This Low Pressure Rehash

“Study hard what interests you the most in the most undisciplined, irreverent and original manner possible.”

– Richard Feynman, November 30, 1965

shear_vel_jam

At the time I had absolutely no idea I was looking at a representation of sheer-jamming in two-dimensional granular materials with power-law grain-size distribution. At all. To me this was obviously a portafilter, those big circles were boulders, the small ones fines, and the picture was showing me the school of tamping towards maximum density was rather flawed. “Hopefully that is interesting?” Christopher Hendon had asked me, and after staring at it for a good day or two, I thought I saw what was so interesting. But to be honest it was really Hendon who told me what was interesting, so I’ll just quote him: “what matters is the difference between particle A and particle B, and then what matters is not how hard you push, rather the forces at their interfaces. And as you can see, this is inhomogenous.”

Computational representations of ice seem pretty far removed from coffee, but if you replace jamming with tamping and ice with coffee, you realise quickly the physical interactions of jamming and tamping, ice and coffee, are the same. The x and y axis on the picture are spatial co-ordinates, so it was easy for me to see that when force was applied it was distributed towards the centre. The more force, the less evenly the material was distributed.

But I was still well away from understanding the idea of homogeneity or what forces applied at interfaces meant just yet. I needed data to help tell me the story, so it was time to do some science, retire some filters, and refract.

Ask a Good Question

So Hendon may be a computational chemist with a pretty good by-line in old-school platinum chemistry and electrocatalysis, but he’s also provided some damn good presentations on coffee. In his presentation “Performing a Good Experiment” Hendon says that to be a good experiment, you need to ask a good question. I thought I had a damn good question to ask: can you make better coffee with higher extraction yields and less variance at low pump pressure, compared to 9 bars? So I lowered my pump pressure to 6 bars, and started taking samples. Hendon had already told me that I’d get a higher extraction and less variance if I did this, but I still think he was a little surprised I took him at his word and went for it. He was right though – my extraction percentage went up, and my variance went down.

How much? Over 20 samples (n) at 9 bars I had an average (M) extraction yield (EY) of 19.08%, with a standard deviation (SD) from the mean of 0.72%. At 6 bars this was M = 19.58, SD = 0.33, n = 20. This was a statistically significant difference (p = .018) with my variance dropping by over half. And taste? Never been this good. This was at a 1:1.55 ratio, as this was how we’d always pulled our shots, and I had never reached great tasting extraction yields at a more progressive 1:2 ratio. I had a strong feeling though I could raise both EY and flavour by stretching those shots out at low pressure, but I was also mindful of another part of Hendon’s “Performing a Good Experiment” presentation: determine your dependent and independent variables.

Know Your Variables

So what were my variables? Dose, time, and yield seemed obvious, with dose being set at 20g for a 20g VST basket. Time and yield were triangulated to achieve at a 1:2 ratio of 40g in 30 seconds – straight out of 9 bar theory and one I had never really questioned. All my initial testing was set up to achieve these metrics.

There was also brew temperature, or the temperature set at the boiler for our La Marzocco GB5, and that was set to 93˚C – again, never questioned, that’s just where you set the temperature at 9 bars. Sometimes higher at 94˚C – I’d even worked with roasters who demanded 96˚C set on the machine – but ever since starting with the Mythos it made sense to me to lower brew temperature slightly to compensate for the heated grinds.

Roast age was important to me as far as degassing goes – so I made sure I always used beans 10 days post-roast leaving adequate time to de-gas, and before flavour fell off a cliff after day 14. I had no Scace device at the time, so I could only ensure at 9 bars the dial read “9.5” with three groups engaged, and down low read “6” with three groups engaged. Before each morning of testing I’d set the volumetrics for my ratio using scales, each group individually set. For initial testing I used a Pullman 58.5mm tamp, and my entirely scientific manner for determining tamp pressure was to place my thumb and forefinger halfway down the outside of the side of the tamp, and stop when the tips of my finger hit the top edge of the basket. My method of grinds distribution, including collapsing, I laid out in this post here. Testing with the refractometer followed Matt Perger’s technique here, with a few more added alcohol wipes in between and plenty of sample stirring – oh, and a small fortune in VST filters (thanks Roger!).

I’d ride out the first hour as the grinder warmed up and service got busy, then I’d randomly start pulling shots off the bar. I decided I’d have a +/- 0.1g tolerance with 20.1g my target dose, as I wanted to mimic real-world conditions – also why I was randomly pulling shots during service. I had no desire to create “laboratory” conditions as I wanted my results to be indicative of how I ran my shop, not how I ran a lab. You could consider that a weakness or a strength, but I was never intending to have these experiments submitted to a journal for peer review – I was doing this to help me make better coffee. In my mind internal validity – or the ability to compare my results between my experiments – was an important factor to maintain.

With that in mind each evening before testing I would tear apart the Mythos, wash the burrs with soap and Isopropyl, then align them as best I could. I also wrote how to do that here, and if you’re a Barista Hustle Facebook member (you should be!) have a look at Mat North’s amazing pictographic post for Mythos alignment. And go get to whale hunting …

I usually cleaned my burrs every fortnight, after around 100 – 120kg coffee. Mat, on the other hand, cleaned his every 8kgs. Consider my results then to be at one end of a spectrum. For comparison sake however, during one lot of testing before cleaning the burrs I had an EY of M = 20.24, SD = 0.29, n = 10, and after cleaning M = 20.75, SD = 0.16, n = 10. I was running tests every week at this point, so this was five working days difference – half a percentage in extraction yield added from cleaning the burrs with soap and aligning. I can’t tell if it was just cleaning that added that half percent, or just alignment, or both together – unfortunately there was no way I was going to be at work for the eleventh hour pulling apart the Mythos and not make it worth my time. If the burrs came off they were cleaned and aligned. I have other tests where I didn’t use filters, and they showed the same trend – at least half a percent difference, sometimes a full percent, in EY pre- and post-clean and alignment. What those results didn’t show however was the difference in clarity. My coffee simply tasted better after cleaning and aligning.

Did you notice the variance as well? 0.16? I got that down to 0.02 for one test the week after this lot, and after that it stayed well under half a percent – always. And I have the Puqpress to thank for that.

Death of the Barista – First Blood

First blood? Perhaps that was when we decided to weigh our shots, or place temperature stickers on our milk jugs, or use volumetrics to measure our shots, then used scales to do the same. Or was it when we placed timers on our grinders, and soon enough scales will be there too. We’re slowly but surely abstracting away user error in espresso preparation. The Puqpress was always coming, perhaps the Eazytamp lead the way. I remember first coming here to Australia eight years ago and starting work in a small cafe with a lever-like contraption for tamping coffee. And somehow we still have around the Swift grinder with its 2g variance dose to dose. Automation is inevitable, it’s a natural process of evolution, and the Puqpress is part of that evolutionary step.

And I’m happy for it. Because coming home, cooking dinner for my wife, and my hands aching while I cut potatoes is a shit thing to have to deal with. Wringing dry a cloth and pangs of pain shooting up my wrist is a shit thing to have to deal with. Tamping that little bit hard by accident and the pain seizing up my arm for a moment is a shit thing to have to deal with. Going through 10kgs of coffee in four hours while trying to maintain a consistent tamp pressure and high level of energy and concentration, is a shit thing to have to deal with. RSI straight-up sucks and I no longer have to deal with it. Because I have a Puqpress. And it’s glorious. Can’t afford AU$1600? Get an Eazytamp 5 Star Pro. Your wrists will thank you.

The Puqpress comes with a stock standard 58.3mm tamp, but I asked for a 58.5mm tamp – I wanted to make sure I could maintain my internal validity with the Pullman tamper. It has an adjustable tamp pressure, going up in 1kg degrees, from 10kg to 30kg. I set mine to the lowest setting of 10kg as I wanted to grind as fine as this would allow me, which is also why I stopped collapsing and just kept to palm-tapping. Day 10 post-roast, burrs washed and aligned, I started taking samples that morning: M = 20.18, SD = 0.02, n = 20. Yield? In grams, M = 38.9, SD = 0.75.

Was that the Puqpress, low pressure, no collapsing, 58.5mm tamp, or all combined? Fuck knows – that’s the realm of multivariate statistics and a) I probably don’t have big enough a sample set, b) I’d need better and tighter laboratory conditions, and c) fuck multivariate statistics. It’s the last subject out of three statistic papers I’ve had to take for my Behavioural Studies degree, and I guarantee you the only way I passed the previous two was because you’re allowed a double sided A4 piece of paper into the exam, hand written or typed, with whatever you want written on it. You better believe I had that in 6pt type, margin to margin, and highlighted the shit out of it – and so far I’ve got Credit and a Distinction out of this strategy. Defining, testing, and analysing the variables involved in coffee is a problem yet to be figured out, but it will be by multivariate statistics – and that’ll be the cornerstone of super automatics, but not this post. With the Puqpress in place and believing all my variables were now neatly lined up, it was time to answer the original question and pit 9 bars against 6.

Nine Bar vs Six Bar

Day 10 post-roast, burrs washed, burrs aligned, and for the first time in three months I was raising the pump pressure back up to 9.5 on the dial. With my 4oz cups neatly stacked atop the machine, I started pumping out 20 samples during service after an hour of warming up.

Some problems immediately presented themselves. My metrics were simple enough – 20g dose, 40g yield set with volumetrics, in 29 – 34 seconds. I’d already decided to reject any shots outside these metrics, along with any visibly channeled shots, as this is what I’d do during a normal service. Within 20 shots I already had three rejections for long or short shot times and four rejections for visible channelling. This was kind of unique – I could not recall a single instance of channelling in those three months at 6 bars, and now I had four within 10 minutes. Strike one for variability against 9 bars, strike two for failing to consistently hit the shot time metrics. I also hadn’t realised how coarse I’d gone at 6 bars as I was far finer now at 9 bar. Otherwise the shots poured fairly well, and while they didn’t taste great compared to what I’d been drinking down low – they didn’t taste bad either. I wasn’t expecting that. But hey – more surprises were on the way.

At 6 bars, and besides an annoying five minutes dialling in to a coarser grind to hit my metrics again, there were precisely zero channeled shots, and precisely zero falling outside the shot time metrics. Two hours later I had 40 shots pulled, lined up in front of me and neatly labeled, and it was time to refract.

Results

9 bar: M = 20.32, SD = 0.26, n = 20

6 bar: M = 20.41, SD = 0.17, n = 20

The yield SD for 6 bars was 0.83g compared to 1.17g for 9 bars, so there was that at least. Time was negligible really, 0.09 seconds separating the two means with a slightly higher standard deviation for 6 bars.

Fuck Refractometry

I raged at this result. For days. To see a statistically significant difference between the mean for 6 bars compared to 9 bars a power analysis told me I’d need a sample size of at least 80, four times what I had. And even then I thought it wouldn’t fucking matter – 0.1% difference in extraction yield would mean nothing to anyone casually looking over the results, especially when we’re lead to believe a higher extraction percentage equates to a better result, and forget about the flavour.

But the shots at 6 bars tasted better! But how do I convince you, the reader, that my subjective taste experience was better than the scientifically objective numbers the refractometer was showing me? I told anyone who would listen how crazy it was we can only measure “how much” we extract from the coffee, but we can’t measure “what” was extracted. Because whatever flavour compounds low pressure was extracting, it was subjectively better than 9 bars in comparison. But I have no objective evidence to prove that statement, because we rely on what really should be called a qualitative measure than a quantitative one. It was fucked.

And I would have continued to rage after these results, and more than likely I would have run that experiment of 80 shots at 9 bars, 80 shots at 6, and proven there was a statistical difference between the two. But I didn’t need to because Andy Schecter had already run his own experiment. His experiment helped crack open the door to figuring out this low pressure lark, as he’d already provided a solution for me.

The Effect of Bean Origin and Temperature on Grinding Roasted Coffee

All coffee ground shattered statistically the same, independent of processing method, degree of roast, and origin of bean. Cold coffee makes a more narrow fines spread. Dot point summary of Christopher Hendon, Matt Perger, et al’s peer reviewed study released in Nature two months ago. Also known as “Bad News For Mythos Owners”. Heat, according to this study, was not a good thing for shatter transitions.

With beans starting from around eight to nine days post-roast and organising them into batches, cleaning and aligning the burrs regularly, setting volumetrics daily, VST baskets, 10kg tamp pressure from the Puqpress, and a low water debit and low pressure – I knew heat was bad news because I still had variance. The grind temperature was one of the last variables left for me to figure out, but at least it was within a known range. Low pressure, along with my other controls, had a huge effect on mitigating any variance caused by the Mythos and it’s heat element. That was the main reason why I dropped to low pressure in the first place – to mitigate any variance caused by unpredictable shatter transitions of the beans at high temperatures. Variance caused by heat was a non-event for me.

But Andy, while busy changing the coffee lexicon from flow rate to water debit, or producing point of view videos of his EK43 prep, had also decided to do a test with beans at low temperature and room temperature. He wanted to see if he could replicate the results of Hendon et al’s study.

In his mind he didn’t have any luck. In a three-by-three test, performed twice, comparing room temperature beans at 20˚C to frozen beans at minus 16˚C, Andy found a negligible difference in EY. To me though I felt this absolutely proved the theory. There was a 34˚C difference between the two conditions, and yet the frozen beans still achieved a comparable result to the room temperature beans. Thinking these results through, I couldn’t help but think of my own experiment.

Because to me the frozen beans achieving a comparable EY to the room temperature beans was along the same lines as 6 bars achieving a slightly higher extraction yield than 9 bars – with a coarser grind. Temperature a known driving force for extraction – but so too is surface area. More surface area achieved through a finer grind should correlate to a higher EY. Conversely, a coarser grind should correlate to a lower EY. Yet in my test, the average EY at 6 bars was 0.1% higher than 9 bars. Maybe there was something to this low pressure lark after all, all I needed to do was pull this string a little further.

Remember Kids, Extraction Percentage Ain’t Nothing But A Number

I remember the first week Matt Perger opened up the Barista Hustle Slack to the general public. There was utter and absolute radio silence that first week. And if any of the other 1000 or so people who signed up were anything like me, they were silent because they were scrolling further back through each page. On every channel they would’ve found knowledge being dropped from Matt himself, and from World Barista Champions, World Brewer’s Cup champions, luminaries of our industry, and veteran baristas and roasters. Fuck me, learning espresso as an 18-year-old all I had was a ripped, tatty, stained-to-shit copy of David Schomer’s “Espresso Handbook” along with a bunch of voodoo hand-me-down dogma bullshit to contend with. I had to sift through shit managers beside shit roasters with shit baristas trying to find the tiny, fleeting, shiny gold nuggets of wisdom that shed some small shimmering glimpse of light inside the inner frustrating mystique of espresso. And these nuggets were now being tossed out left and right like candy. And I chowed down on that shit like a kid on a cupcake. It was glorious.

The Barista Hustle Slack was, and still is to a lesser degree, a brilliant medium for communication between peers, and a great way to foster a community around creating great coffee. Seeing Christopher Hendon readily reply to questions and queries on the #water channel motivated me to message him privately, ultimately leading me right to this point here. But the BH Slack quickly became a small satellite orbiting the behemoth that became the Barista Hustle Facebook page, and wandering into my attention on a post about low pressure came Mat North, from Full Court Press, in Bristol England.

We started conversing, I showed him the results from my experiment, and he reminded me of his post here, and how the extraction percentage is just a number – it also needs to be correlated to taste. I’d been chasing high numbers, going for those marginal gains, and I hadn’t really been paying much attention to taste. To illustrate this point, Kegman Kipp, way over in California, had asked me to pull a 1:3 EK style to see what I got. I achieved a 23% mean over five shots – and every one tasted horrid. Sure, easy strawman there to create, but it reminded me (and that’s what chasing high EY numbers do to you – you forget) that flavour should be king. Chris Baca showed here how a refractometer should be a tool to guide your palate, Scott Rao showed here how that tool can be used, and Matt Perger said himself on the BH FB page – “More extraction + better flavour = better”. Note the “+”. I’d missed that momentarily.

Kipp was one of the first people I contacted on Slack, and we struck up a productive friendship over our shared usage of the Mythos. He lowered his pump pressure when I asked him, and his results mirrored mine. This was however only after turning off his pre-infusion. For a month he was getting glimpses of the flavour low pressure can provide – but he was living half in the 9 bar world, and half in the 6 bar world. Low pressure demands commitment – pre-infusion needs to be off.

We would occasionally have conversations about him swapping over to an EK43 but he kept coming back to one simple point: he bought the Mythos because, in his own words “3 OG WBC champs and an Irish bloke WBC 4th placer have pretty good taste buds”. In his mind solubility created by the heat was the ticket to why Mythos espresso tasted so good. That stuck in my mind.

Finally, into the conversation Gregory Scace walks – so famous they named not one, but two pressure and temperature measuring devices after him. In two replies to Andy’s experiment he finally allowed me to fully understand that picture Hendon had originally sent me. In a moment of clarity in the middle of the morning rush, floor packed with customers, death-stares everywhere, on top of the grind, adjusting coarse and fine, wiping the tray, raking beans forward, stacking cups and smashing shots – solubility, heat, tamp pressure, pump pressure – it all finally made sense to me.

Fuck Yeah Science

The issue with describing an extraction as even, Greg explained in his reply, is that there’s actually no such thing. The temperature at the top of the puck is equal to the brew water temperature, but “the coffee at the bottom of the coffee cake comes nowhere near it – ever”. Factor in a seven degree change in temperature at the bottom of the puck compared to the top, he continued. Heat is a known driving force of extraction, so at the top of the puck the coffee is being extracted, but cooler water at the bottom makes extraction there a lot harder. But a solution of coffee and water is being created at the top of the puck – what I guess we’d call the actual “espresso” – which has to make its way through the rest of the puck out into the cup at the bottom. The concentration of this diffusion is called, funnily enough, the concentration gradient – which is stronger at the top of the puck than at the bottom. This further complicates extraction at the bottom as the water getting through at that point is actually a mixture of dissolved coffee solids in colder water – so you’re basically shit out of luck extracting flavour from the bottom of the puck. This idea is not new, Maxwell spoke about this in his post here, asking us to think about what our real dose is. How much, he asked, of the dry dose is actually being extracted during the espresso process? So really, what’s your real dose, and what does this mean to your extraction percentage read from the CoffeeTools app?

But in that moment of clarity behind the machine, Kipp’s idea of solubility hit me. As the grinds were already hot, the difference in heat between the brew temp and the grinds temp was smaller so equilibrium between the two can be reached quicker than if it was lower or more variable. Faster temperature equilibrium means the water can get to work on extracting flavour from more of the coffee faster than if it were lower. As it was already at a higher temperature at the top of the puck then water at the bottom wouldn’t be as cool either. Mat North had said that with the Mythos at least the grinds were within a known temperature range. We didn’t have that before, but the Mythos constraining temperatures to under 50˚C, now offered us this information.

So the brew temperature of the water was able to reach the bottom of the puck faster, adding to the already sped up extraction at the top of the puck. But could we make it reach the bottom faster, and in an even fashion?

Is that picture making sense yet? Again, from Hendon: “what matters is the difference between particle A and particle B, and then what matters is not how hard you push, rather the forces at their interfaces. And as you can see, this is inhomogenous”. Inhomogeneous? That would be the forces at the interfaces of particle A and particle B. Those particles? That’s your particle size distribution, and grinding finer creates a larger amount of little bits, and a smaller amount of bigger bits. If you follow the pictures on that original link, you’ll see how finer particles essentially distribute themselves evenly into a confined space with some slight agitation. In this case the confined space would be a portafilter, and we’ll just go and call that slight agitation “palm-tapping”. Tamping hard or towards “maximum density” creates inhomogeneous or uneven forces at the interfaces of the particles. So when pressurised water arrives the velocity of the water will be uneven, as it’s passage through the puck is past areas of uneven packed force. Uneven passage creates variable extraction. What’s needed is an even distribution of energy throughout the puck – a controlled tamp pressure.

In my case I had the Puqpress, Kipp had the Eazytamp, and in both cases we were tamping down at a controlled 10kg of pressure. I tried at 20kg and ended up with a mean of 19.46, SD = 0.43, n = 10. At 30kg I didn’t even bother testing – nothing emerged from the portafilter for over a minute, and adjusting the grind at 6 bars gave me coffee grinds looking close to French press. 10kg seemed to be the optimum tamp pressure for 6 bars – I’d hazard a guess this tamp pressure would change dependent on pump pressure, and would be why we grind fine and tamp hard at 9 bars. The world’s a different place down low however. Down low we grind fine and tamp light. Kipp found great results on the West Coast; I found great results in Queensland.

But grinding fine, while we know allows for a greater surface area, also creates resistance to the pressurised water. And at 6 bars that resistance is close to nothing compared to 9 bars, so consequently the shot time will blow out. But Greg also pointed out another essential feature needed for a consistent espresso extraction – time. Surface area, heat – and time. So it didn’t matter if our shot times blew out past 30 seconds. We could compensate for that with the brew temperature, bringing it down slightly so the extended “dwell” time the puck would have with the heated water wouldn’t over-extract our shot. I was already at 93˚C, taking it down half a degree to 92.5˚C, while extending my shot time to 40 seconds, gave me my best result yet: M = 21.06, SD = 0.30, n = 10. If I thought it couldn’t taste any better than I already had it, this espresso was beyond amazing. This was no longer about marginal gains – it felt like a different coffee.

But Mat wasn’t finished with me, saying. “I reckon if you lowered your dose, your EY would be even higher”. It took me a while to understand what he meant, but when I did, it made sense – a lower dose meant to hit my shot time of 40 seconds, I’d have to go finer again. Not only that, but setting my tamp pressure to 10kg would mean I’d have to go even finer again to compensate for the lighter tamp by comparison. Finer upon finer and I’d have a much greater surface area, and extracting within the same time limit I just lowered my volumetrics slightly to keep my 1:2 ratio.

That volumetric compensation was pretty shit – I set the weight a little shorter than I should have – and I hit a 35g average compared to my target 38g. Which would probably help explain why I was down to a mean of 20.28% EY, SD = 0.30, n = 10.

But don’t forget kids – extraction percentage is just a number. Let me instead try and explain that morning to you.

Ctrl-Alt-Delete

So this is it. If you’ve followed me all this way I’d like to commend you for your perseverance getting though not only this small novella, but also the two other parts of the trilogy here and here, with a slight departure here. During this time I’d like to think I’ve built up at least a small modicum of trust with you, because that’s all I have to trade on when I describe what happened that morning.

The recipe was simple: 6 bar pump pressure, 10kg tamp pressure, 92.5˚C brew temperature, between 40 – 50˚C coffee grind temperature, 19g dose in a 20g VST basket, 38g target yield, 40 second shot time. Staff member number one arrives, I pour a doppio for her, she takes a sip, frowns, looks at me and asks “what’s this?”. I ignore her (I can be a shit boss sometimes …) and instead fire back “how’s it taste?” “Amazing” she replies. “What single origin is it?”. I smile back. “It’s our blend”. She frowns and keeps sipping. If you can imagine a metaphorical ctrl-alt-delete being performed on someone’s brain, that was what her face was showing me. I completely understood – the first shot I pulled for myself earlier I had one of the tradies working in our building come up to chat with me. I have no idea what he said. I was staring down at my cup, trying to comprehend what I was drinking. Sweet, dense, lip-smacking acidity, voluptuous, concentrated, complete ctrl-alt-delete, reset my brain, because what the fuck am I drinking?

Staff member number two arrives, I pour another doppio. He sips. A slight grin emerges coupled with a frown. Ctrl-alt-delete. “Ok” he says. “What am I drinking?” “Our blend” I reply. He laughed slightly, not moving from that spot, a full two minutes of silence from him as he occasionally closed his eyes looking down at his cup, sipping away. Ctrl-alt-delete.

The owner arrives, we’re busy now; I pull his shot in between customers and hand over a piccolo to him. He sips, looks back, his frown bordering on confused anger. “What the fuck is this?”. I smile back, “how’s it taste” I ask him. “Holy shit” he says as he puts his glass down on the bench, finger pointing at it accusatory. “That” he points again at the glass. “Is the best damn coffee I’ve had here. Hands down. I can’t remember a coffee like that before. Holy shit. What’d you do?”

What did I do? I just followed down the path Hendon sent me on, and physics provided the details. It’s quite possible I’m interpreting those physics wrong, or attributing characteristics to mechanisms that don’t work the way I think they do. So call this my interpretation of low pressure theory – in the end it works in the cup, and it makes sense to me. I’ll let you figure out if I’m wrong, but here’s a recipe for you to first try at least.

Low Pressure Rehash Recipe

When we used to “dial in” every morning, it would always involve adjusting the grind to hit our 30ml in 30 seconds, 9 bars of pressure, 93 – 94˚C, tamping as hard as we could or at “30 pounds of pressure”. Then we got scales in, ditched Mazzer’s for EK’s, changed our ratios up to a 1:2 or more, weighed grams in, weighed grams out, extended the circumference of our tamps, nailed temperature stability for our machines (mostly) – but all this and we were still dialling in with incomplete information. You never adjusted brew temp, you had no idea what temperature your grinds were, and you had no idea if you were tamping at a consistent pressure. If you did experiment at low pressure, you probably adjusted the grind coarser, tamped hard, kept the brew temp at 94˚C, extracted in 30 seconds or less – and you would have come up with an under-extracted terrible tasting espresso. Tamp pressure and grinds temperature, in tandem with low pressure, never made it into the conversation because we had no idea what the fuck they were.

But now we do. And with that understanding we can really start to dial in our espresso.

Let’s start with pump pressure. But first you can’t keep water debit out of the conversation as it’s essential to your pressure. Think of watering your garden pot using the garden hose with a sprinkler attached, then replace that hose with a firehose – that’s the difference between a slow and fast water debit, and a nicely watered plant and one blasted over the neighbours fence. It’s a measure of volume of water delivered within a certain amount of time, and a good metric to try and hit is between 200 – 280ml in 30 seconds. Before lowering your pressure use the right tool for the right job and correct your water debit with restrictors – if you can. Which I hope you can. It’ll make your espresso taste better at 9 bars and simply magical at low pressure. It’ll also give back the body and thick mouthfeel you may feel you lose compared to 9 bars, while making your extraction more consistent. It’s your water debit that feeds your pump pressure, enabling that consistency. With a low pump pressure and slow water debit in place there’s a few things now you can achieve which you can’t at high pressure:

  • We get a slow movement of water through the puck – let’s call this velocity. This allows both diffusional and temperature equilibrium throughout the puck. This is mainly at the top of the puck still, but more at the bottom if you have a known raised coffee grinds temperature. Through that temperature you have a lower dissipation of heat as the water passes through the puck.
  • You also mitigate any variance caused by imperfect technique – I’ll send you the video I took if you want where I dug a 5mm divot into the surface of a puck, pulled a shot, and while it did show the water initially rushing to that corresponding point beneath the basket –  it never came gushing out or overtly channeled. Within milliseconds the rest of the espresso started forming on the bottom of the basket as well. The next shot I pulled sans divot, poured in exactly the same time. That’s a 19g dose – 18g or 15g, as Mat or Maxwell would tell you, presents problems for channelling based on how thin the puck is. But still – you’ll get far less channelling at low pressure. In my main experiment I had four in 10 minutes at 9 bars, zero in three months at 6 bars.
  • Not only does low pressure welcome one and welcome all with imperfect technique, it’s also forgiving of variable particle size distribution – again, because of velocity. Slow movement means bigger bits extract at a proportionally higher rate than they would have at a higher pressure, as contact time has been increased.

What about tamp pressure?

  • “Even distribution of force throughout the puck” is another way of saying “even force applied at the interfaces of each particle”. So the tamp pressure needs to be light enough to not introduce uneven force at these interfaces. 20kg was too much, 10kg produced amazing espresso. It could be that 15kg might do the same, or even the original 30 pounds, or perhaps even as light as 5kg. But it needs to be reproducible – and that’s what products like the Puqpress and Eazytamp provide – reproducible and consistent tamp pressure.
  • This consistent tamp pressure means the low pressure water is not meeting uneven resistance throughout the puck – it has a clear passage to the bottom, meaning we now have a true velocity, set by the pump pressure and fed by the water debit. You never had this clear passage before, it was always muddied by imperfect tamping, collapsing, made worse by high pressure. So now we’re extracting from a larger percentage of our puck than we were before, as the water has a clear and consistent pathway through.
  • A lighter tamp also means a finer grind. A finer grind means we can control the  water velocity, thereby controlling the extraction time as a function of temperature and diffusional equilibrium, while also gaining more surface area.

And brew temperature?

  • This is a function of how we dial in at low pressure. A fine grind slows down the water velocity, while a high grinds temperature produced by the Mythos speeds up temperature and diffusional equilibrium. So we run the risk of over-extracting when using the Mythos. Half a degree down – for me – compensated for this.
  • What if you’re using frozen beans? I do at home, and its great – it gives me a known temperature as well as an even particle size distribution. So I go in the opposite direction, 94˚C.

And time?

  • Again, we’re dialling in with complete information now, so time needs to be experimented on, with the understanding that we need to provide enough time for temperature and diffusional equilibrium while compensating for the finer grind slowing down velocity. It will hit an equilibrium however, and once it’s there, extraction really begins. So for me, that took 40 seconds before I started encountering slightly bitter, dry flavours characteristic of over-extraction. Frozen beans were completely different. I ground fine enough to choke a Slayer and had some pours upwards of 1 minute 20 seconds. And it tasted great.
  • Can I draw shot times out at work to 1 minute 20 seconds? Fuck no! Going up to 40 seconds was rough enough getting though 500 cups in a morning. An extra 10 seconds was a lifetime. But I adjusted – not just in workflow, but in dialling in. Brew temperature was kept constant at 92.5˚C, grinds temperature was constant between 40 – 50˚C, pump pressure was constant at 6 bars, tamp pressure was constant at 10kg, dose was constant at 19g, yield was constant at ~38g –  and all I changed was the fineness of the grind to hit 40 seconds.

And dose?

  • VST recommend a +/- variation of 1g – so I took them at their word and shot down to 19g. VST baskets are manufactured to promote faster flow through the basket by having more filter holes than stock standard baskets. So already you’re going fine to compensate for this faster flow and the restriction it causes. Now you have a lower dose with less depth for the water to penetrate, which also leads to a faster flow. So you grind fine again to compensate.
  • How does this affect acidity? No idea – but it does. In an amazing way. In a previous life when I was selling wine I always held acidity to be the backbone of a great wine – not to be confused with screw-your-face-up sourness. Instead you should be looking for lip-smacking acidity. It holds up all other flavours and suspends them there with full clarity. It’s no different with espresso, and that one gram drop in dose made the acidity shine.

And that’s the recipe, that’s how you dial in with complete information. You’ll need to experiment, but it won’t take more than a few shots to start seeing what direction you need to go in. Trust your tastebuds, correlate with a refractometer, and try and understand all these variables as sitting on a spectrum. You just need to find where on each spectrum your coffee, roast degree, machine, and grinder, can get you.

Conclusion

When viewed through this lens this low pressure rehash is really a clearer understanding of the relationship between variables. Water debit is related to pump pressure. Pump pressure is related to tamp pressure. Brew temperature is related to the coffee grinds temperature. Time is related to fineness of the grind. These variables combine to influence your ratio, while also promoting or demoting successful temperature and diffusional equilibrium. Physics guides all of this.

If I’m going to quote everyone else, I may as well quote myself here, as I’ve said this before and I feel it needs to be said again: “none of this is really new, it’s part of basic espresso theory we’ve all been taught … What is new is our understanding of the physics involved, and for that we need a new paradigm of thinking.”

I’m not alone in this thinking. Mat has written a brilliant piece here, outlining his own experiences with low pressure, with his thoughts on the possible mechanisms involved. I share and agree with them all, and while I may not yet fully understand the “how” – I know what it tastes like in the cup. Perhaps consider these two pieces the first sentence in a broader conversation, continued on by anyone else who decides to untwist the nut and go low.

It took me three months to cast off the shackles of 9 bar theory, lower my pump pressure and my brew temp, under-dose, tamp light, grind fine, and pull long. Along the way I’ve had the immeasurable help, either outright, tacitly, or unknown, from Christopher Hendon, Mat North, Chris Kipp, Matt Perger, Andy Schecter, Gregory Scace, and many others. But it was always the physics that lead me here. This low pressure lark is not a rehash – it’s how espresso should’ve always been made. It’s just taken us a while to get there.

Michael Cameron

(Agree with me or not here on Twitter, and find answers to questions like “what did Michael do at work today?” on Instagram here – every like gives me one more VST filter to use …)

 

Hashtag Mythos Workflow

“A symphony is no joke.” Johannes Brahms, 1833 – 1897

It was Colin Harmon and his Tamper Tantrum presentation that got me interested in the Mythos One. His matter-of-fact delivery and seductive Irish lilt, accompanied by his persuasive post here, convinced me this was something I wanted to try. When our coffee supplier, Supreme Roasters, offered us a Mythos One as a replacement for our ailing Mazzer, I jumped at the opportunity. I’d spent the best part of the past decade dealing with Mazzer’s. I was done with them.

It’s been on our bar for over nine months now, full time, five days a week, going through around 60 kilos a week. This has given me ample time, a large sample set, and a huge amount of empirical data to find a system that for me is fast, efficient, consistent, and produces excellent espresso. When I first started researching the Mythos One, Colin’s voice was the only one I could find that was really meaningful for me, beyond an incidental rehashing of the press release followed by a spec list. Google kept coming up short, so call this my contribution – apologies in advance for the cursing and poor humour.

Thou Shalt Clean the Machine as if It Were Fresh From The Factory

This is your starting point, Espresso 101 – you need to ensure your machine is clean, cleaned regularly, and cleaned thoroughly. This piece from the Daily Grind covers pretty much everything I would say, with the added emphasis of clean your fucking machine. I know it’s hard, we’ve all been there – but at the end of your shift that’s when you dig deep and do a professional job. And clean your fucking machine.

I always, always, spend at least two shifts, usually three, closing with new recruits. This is not just to show them how I want the machine cleaned, it’s to show them how to do a shitty, tiring, and repetitive job with some goddamn dignity. To do it without complaining. To stick their head down and just get it done. And to do it right, each time, every time. I know with my staff that I don’t need to worry about how clean the machine is. Like knowing if the sky is blue and the ocean is wet, my machine is clean, as if it were fresh from the factory. But a clean machine also demands the respect of good tools.

Craftsmanship Requires Good Tools

So I’ve already spoken about VST baskets here, so not wanting to rehash the argument – just get some VST baskets. I like this post here by Five Senses, which explains their experience with VST baskets (and also contains some valuable information on dose, head room, and consistency). Please – use VST baskets.

While I’ll stick to my assertion to not use IMS baskets, I can wholeheartedly recommend IMS shower screens. I think it’s arguable what they can achieve in terms of higher extraction yields (does anyone have any objective data and comparisons yet?). However, what they do empirically achieve is less need for cleaning. Whether it be the coffee gunk that gets in between the mesh and the holes in traditional screens, how much coffee sticks to the screen after each shot, or washing it clean at the end of each shift – IMS screens are just easier to do this with. If it’s easier to achieve cleanliness, then we are aligned with the idea of “clean your fucking machine”. Not everything we do has a first order effect on extraction yield or subjective taste such as VST baskets. Sometimes second order effects – like cleanliness – mean we have a cleaner “canvas” to work on, meaning a clearer picture towards higher extraction rates. Being easier to clean also leaves more time for you to scrub the shit out of the bottom of your portafilter …

(#Pro-tip: might I also humbly recommend if you do not have Teflon or other coatings so the oils don’t stick, if you’re stuck with the black pitch of oil each afternoon stubbornly stuck to the portafilter, that you use 3M Scotch-Brite – not the cheap knock-offs – wait for the portafilter to dry out on it’s own, then vigorously scrub with a dry Scotch-Brite. The friction created from both dry surfaces, and whatever voodoo 3M uses to differentiate their green scratchies from the rest, has an immense effect on the built-up oil, essentially rubbing it straight off. Remember the moment you first use 3M Scotch-Brite on your portafilters. Your life will forever be divided into pre-3M and post-3M. But stay away from the outside chrome – it’s nice to keep that shiny for as long as possible …)  

Tamper Size Matters

I’m well aware of Socratic Coffee’s post on the effects on tamper size. I think it’s great what Socratic are doing, I understand the experimental design, and I believe the objectiveness they sought with this design has been achieved. But for me, I wouldn’t base a decision on ten samples or draw any conclusions from it – I’d be questioning it.

I have found a significant difference between tamper sizes, and I’m not alone. Matt Perger has placed his considerable reputation and name behind the belief tamper size makes a difference. There’s Greg Pullman himself manufacturing 58.4mm tampers and above, as well as VST also selling 58.35 tampers (+/- 0.1mm). The inimitable Chris Baca writes about his experience here, and Ben Kaminsky explains his testing achieved higher extraction yields with at least a 58.4mm tamper in this talk here. Then again, Mat North didn’t find a significant difference. Empirically I’ve seen better results from naked portafilters using a 58.5mm tamp, and far less channeling – so if you conclude yourself from Socratic Coffee’s post that tamper size has no effect on extraction yields, look to the second order effect of less mess in the cup, and less wastage from channeling. Lack of channeling should be reason enough for any barista to go with at least a 58.4mm tamp, but taste the results yourself, see it in action, retire some filters and refract the shit out of some samples. Experiments should have external as well as internal validity, so if they found no significant difference in extraction yields based on tamper size, then so should you. Or perhaps not, and that’s all part of the scientific endeavour.

In so many research papers I’ve had to read there’s always what feels like a disclaimer at the end of the conclusion: “more research is required”. So can I politely ask: “Can we have some more data please?” Shit, I’ll draw the conclusions myself.

How Low Can You Go? (Redux) 

Before getting to your Mythos you first you need to understand what it actually does. Through heating the burr chamber the beans are kept between 35 and 45°C. This, along with having no outside vein on the burrs like an EK43, means the Mythos does three things rather definitively – it reduces fines and produces a unimodal grind profile, while allowing the beans to become more soluble. Less small bits, more big bits, and solubility allowing water easier access to extract flavour.

Combining these three features you may find that by lowering pump pressure (mine’s at 6 bars) you’ll allow yourself to target the big bits for an even extraction, increase temperature and diffusional equilibrium, and lower any inherent variability in your technique. I’d strongly recommend to any Mythos owners to lower your pump pressure if you can, or at the very least start playing around with pre-infusion profiles.

A Clean Mythos is a Happy Mythos

So – a clean machine, VST baskets, IMS screens, a 58.4mm tamp (at least), and 6 bars of pressure – that’s your starting point to now begin examining your actual grinder. You should be keeping a close eye on how much time it takes to grind a dose. Yes it will change with different beans, blends, roast age, and hopper level, but if you notice a steady increase your dose time then it’s probably time to clean the chamber out. You can avoid the guesswork entirely by scheduling regular cleaning – which I always do this once a fortnight. I’d do it once a week, but alignment (which I’ll get to in a moment, and is needed after cleaning) is a pain in the ass. Plus I have to do it after service. Which means an eleven-hour day at least. And I’m getting old; I really can’t be fucked with eleven hour days anymore. But like your machine you need to clean your grinder. So make the sacrifice.

And buy a vacuum cleaner. Buy a vacuum cleaner and your life will clearly be demarcated between pre-You-Bought-a-Vacuum-Cleaner-for-Work and post-You-Bought-a-Vacuum-Cleaner-for-Work. There is such a significant improvement in Quality of Life, Post-You-Bought-a-Vacuum Cleaner-for-Work.

To start cleaning your Mythos unplug the grinder and remove the hopper (which you’ll clean out with hot soapy water, rinse well with running hot water, dry as best you can, then leave it on top of the machine while you’re cleaning the grinder to finish drying). Unplug the element and then remove the four screws at the front of the burr chamber. I stripped the shit out of the first screw when I initially attempted to remove it, so be careful. And store them somewhere safe after you’ve removed them.

(#Pro-tip: do not store the screws in a takeaway cup and leave it on the bench! They get thrown out with the trash and an hour later you’re knee deep in the dumpster out back going through bags trying to find it while sifting through rotten grinds and last weeks discarded lunch. Happened to a friend, try avoid it yourself)

Once the screws are out you can lift off the fixed burr carrier, exposing the grinder side burr (or whatever the fuck they’re technically called. Look, you got the burr carrier with attached burr in your hand – the static or fixed burr – and you got the one not in your hand, still attached to the grinder – that’s the other one). Unscrew both burrs from their respective carriers; taking care again to place the screws somewhere safe (also clean out the flat head slot and the threads of the screws) and now you should have two shining golden titanium coated burrs in your hands. If you have any trouble removing the grinder side burr, which you probably will, don’t wedge a screwdriver into the exit chute to leverage any screws out – use a wrench and hold the auger in place while you unscrew them.

Brush off excess grinds and then wash them. With soap. And a toothbrush. I’m serious! I cover them in detergent, run it under hot water, and scrub the shit out of them with the toothbrush. More hot water, inspect under light, note any stubborn grit stuck in the burr “teeth”, go hard again with the toothbrush, inspect again, then rinse thoroughly under hot water. I dry them as best I can with a clean microfibre cloth and then leave them on top of the espresso machine to dry further. I work on the next, then come back to the first burr. I spray this thoroughly with Isopropyl alcohol, wipe clean with another fresh cloth, spray again, wipe clean again, then set the burr to the side. Literally rinse and repeat for the second burr.

Now the vacuum cleaner! Vacuum the burr carrier out, and use a brush or paper clip to gently prod free any stubborn bits of coffee crud. Vacuum again, clean, brush and prod, vacuum, clean, and so on. Make sure you don’t vacuum directly over the clump crusher though – the oh-so-important piece of plastic covering the grinds exit chute. The interleaved plastic triangles are long enough that if inverted towards the burrs by the vacuum cleaner sucking them up, they will catch on the burrs later on.

(#Pro-tip: if you didn’t have a problem with static before, if you even just touch the clump crusher – you’re going to have a problem with static now. Just try not to even touch that thing until it needs to be replaced …)

I still use a paperclip to dislodge any built-up crud in the chute itself,  and then use a microfibre to clean out as much of the chamber as I can. Shine the torch in from your phone or the like to give you better light, and make sure you have zero coffee grinds on the surface you’ll rest the burrs on. Move onto the burr carrier you removed and clean the shit out of that as well with the microfibre, again making sure there are absolutely no coffee grinds on the surface you’ll rest the burr. Now you’ve cleaned all that you can, it’s time to reassemble and align the burrs.

“… What’s this long face about, Mr Starbuck; wilt though not chase the white whale? Art thou not game for (burr alignment)”

Alignment. It’s the modern day quest for Moby Dick. Only without the revenge factor. And the sea. And an actual whale. There’s no Captain Ahab either, and alignment isn’t exactly a clear comparison between themes contained within a classical piece of literature and modern day mechanics. But besides that pretty much the same. Just with burrs. And no whale.

Alignment is important, but I only learned of it’s importance from these people – so I definitely need to give credit where credit is due, and excuse the cliche but these guys know their shit: Nick (@nickw) and Tom (@dsc) taught me everything I know about alignment on Slack. Nick has a very cool video here, Tom’s advice is littered throughout the entire pantheon of home barista sites it seems, and Spencer (@spencerwebb) has a well-written piece here. I’m adding my own experience here, following the same principles, only applying them to the Mythos One instead.

When talking about alignment there are essentially two directions you need to concern yourself with. There’s radial alignment – which I think of as how one burr can move side to side, up and down, North northeast, or South southwest and the like – and ensuring that within the space they can move allowed by the screw holes, they both perfectly line up concentrically. Then there is axial alignment – how much the burr can move either forward or backwards on an angle – with the aim being to ensure both burrs are perfectly parallel to each other. Let me be perfectly clear here – testing both radial and axial alignment is a fucking brutal. But the results are well worth it. Unlike Ahab you can taste the whale. Ok. These analogies are really falling to shit right now …

So testing alignment is some pretty high tech shit for the average barista. You’re going to need:

  1. A non-permanent marker pen
  2. Scissors
  3. Printing paper, or tin foil
  4. Patience. A whole bunch of patience

For radial alignment on the Mythos, start with the static burr, or the one you removed from the grinder. Attach the burr, then screw in the screws lightly – you should have some sideways movement of the burrs. Now cut three small strips of paper, and place them between the outside of the burr, and the inside lip of the burr carrier, spaced evenly apart by thirds. The lip is quite small, and it’s a finicky affair fitting the pieces of paper in, but with time, patience and dedication you’ll make them fit. If the burr still has sideways movement, remove the pieces of paper – let’s call them “shims” – fold the shim in half, then repeat the procedure. Be mindful of how much the paper or foil can compress as well. Eventually you’ll have the three shims equally spaced apart, and the burr won’t have any sideways movement. Now tighten the screws like you would when changing a tyre – a little at a time for each one. When you think they’re close enough in, remove the shims. This bit sucks as they may be stuck pretty hard in there, and you end up ripping them halfway, leaving half in your hand and half still stuck between the burr and the carrier lip. Don’t be disheartened; just repeat the procedure again, being careful this time to not tighten the screws too far before removing the shims.

The grinder side burr is far more difficult, if only because you have such a small space to fit your fingers and shims and then tighten the screws. Just hold onto that patience. The “shim” point here is on the inside of the burrs, and the outside of the bottom part of the auger. The same process applies, folding the shims if needed so the burr has no sideways movement, placing three shims equally distant around the inside of the burr, and tightening the screws slowly, leaving enough slack so the shims can be safely removed without moving the burr. Your axial alignment is now done.

For axial alignment, start with the static burr or grinder side burr, and only colour in one burr’s edge. Now screw the static burr carrier back in, plug the grinder back in and turn it on, then slowly start turning the dial finer until you start to hear the tell-tale “chirp” of the burrs touching, or “zeroing”. Dial back a little towards the coarse side, unplug the grinder, unscrew the burr carrier, and inspect where the marker pen has been ground off. It should have evenly come off around the entire burr. If not and there’s one section that hasn’t been touched – take a shim, lightly unscrew the burr until you can fit that shim under the burr, directly beneath the area where the marker didn’t come off. Colour in the edge again, plug in the grinder again, screw the burr carrier in again, zero off until the “chirp”, remove again, inspect, shim up again, rinse, repeat, shoot yourself, rise from the dead, repeat the axial alignment, colour in the burr, screw the burr carrier in again, check radial on the static burr, die again, yell and scream into the nothingness, unplug, plug in, face the darkness, find your inner strength, place a shim on the static burr, scream, colour in the burr, scream again, beat your chest, cry, curl up in a ball, rock back and forth, look at the Mythos, wipe away the tears, stand up tall, check radial and axial alignment again, scream once more, align that motherfucker, then go home, hug your wife or boyfriend, kiss the kids, watch some television, have a long hot shower, wash away the pain, clean your aching soul, sleep the sleep of the righteous …

And be fucking blown away by how amazing your coffee tastes in the morning. And look over to the Mythos, furrow your brow, and whisper to yourself “next fortnight Mythos One – we will do battle once again.”

The shitty thing about alignment though, is alignment of your burrs relies on the machined parts of the grinder serving as anchor points for your shims. If the machined parts – the outer lip, or the inside bottom part of the auger – are not machined well, if the tolerance allowed means they don’t line up either concentrically or parallel or both, then you’re shit out of luck getting perfect axial or radial alignment. At least with shims though you’re going to be far closer than you ever could be simply “eye-balling” it and banging the burrs in. So not perfect, no – but closer, and “more” aligned than you had previously. You should taste the difference.

Don’t be alarmed if in the morning your grinder time for your dose goes up. Better alignment means better grinding which means less fines and boulders spat out, and a substantially improved and uniform particle size as a result. This in turn means the beans move slower through the burrs, as they are essentially being “processed” better. Eventually you’ll notice the difference between a post-alignment dose time and a pre-clean dose time, and be able to act accordingly.

About Those Burrs …

They’re titanium coated and touted to last 50,000 cycles, or the equivalent of 1,200 kilograms. My first set lasted 700 kilograms, and there was a marked and rapid decrease in extraction yield that told me it was time to change. So random shots taken off the bar aren’t just tested for tamper size or pump pressure effects, it’s also to graph the inevitable decline of extraction yields as the burrs get used. But be careful to inspect the new burrs when they arrive to ensure there are no dents or scratches in them. My second set were scratched and dinged up pretty bad, and I’m not alone in receiving burrs from suppliers in this state. Burr quality and shipping standards – that’s a whole other rant. But these golden burrs are expensive – make sure you get what you pay for.

Bean Management

Whatever side of the roast age debate you sit on, for consistent and repeatable results from the Mythos – and any grinder for that matter – you need to have some kind of bean management in place. For me, I rest the beans for at least seven days, and aim to be through them by day fifteen at most. I have our roaster also label each bag by batch number two, and I ensure not only that we consecutively use roast dates, but also batch numbers as well. Whatever you do, make sure you consider the impact of roast age and associated gas dissipation on consistency.

As far as first order effects and second order effects go, the level of beans in the hopper won’t have much effect on extraction yields. At three kilos of beans with a full hopper (if you’ve got the big hopper installed) or the last 90 grams in the neck, you should have a consistent extraction yield, all other variables being equal. But you sure as shit won’t have the same dose. The auger is supposed to ensure an even and consistent flow of beans into the burrs, but it’s no that effective really. I’ve actually never found an auger on any grinder that can do this effectively, so let’s not blame Nuova Simonelli for that one.

The clump crusher also has an effect on the flow of ground beans out of the chute, and if it is damaged or clogged up, this will also affect dose consistency. Upon installation of a new clump crusher (and do not do this yourself if you can avoid it. You think alignment is bad? Try installing a fucking tiny piece of plastic in a 1cm small cube of space while ensuring the plastic forks of the crusher face downwards. It is not fucking simple) the forks take around ten or so kilos to “settle” in, from there maintaining a consistent flow of ground coffee out of the chute. But it only lasts so long. To avoid estimations of how may kilos it possibly lasts for, I just change it at the same time I change my seals – once a quarter.

Finally, on older versions of the Mythos One there is a black plastic covering over the exit hole of the hopper. Originally I believe it was thought this would also help control the flow of beans into the auger, and therefore aid consistency. It doesn’t. It’s heat-glued in place and breaks off easily. Rip that fucker off. Just don’t do it when the boss is around – they may freak out.

Because of these three factors, during busy periods I keep the lid off from the hopper and constantly rake the beans forward, so they sit directly over the neck of the hopper. An even weight of beans going into the auger means they will grind at an even rate, allowing for a consistent dose and less time fucking about adjusting your dose. Which fuck extraction yields – that’s why we keep a hopper full of beans in there when we can, Mazzer or Mythos or whatever grinder you’re using.

To Weigh or Not to Weigh?

It’s not even a question – weigh your shots. It’s not hard, it doesn’t slow you down, and the implementation of weighing shots offers far more in consistency, taste, and efficiency – by orders of magnitude more – than sticking to timed doses or just “eye-balling” it. Weigh your fucking shots.

For my Mythos workflow (and Mazzer’s before that) I weighed my shots at the grinder, in a container rather than the portafilter itself. You could weigh the portafilter and have a workflow similar to this at Prufrock. You could use putty, or tape, or something else, to ensure all your portafilters weigh the same. You could take a metal grinder to the portafilter itself and grind off the required weight to equalise all your portafilters. You could get an Ohaus scale or the like, make room on the bar for it, dose into the portafilter using the handy portafilter holder on the Mythos, weigh the shot, go back and have a second shot time programmed to one gram or two, adjust your grind, go back and weigh again, adjust down or up if needed, then tamp …

… Or you could invert the portafilter handle, secure a 1cm thick platform on top, place a cheap eBay jewellery scale on that, and dose directly into a $2 75ml plastic Decor container. The 1cm thick platform is important as it allows you to simply push the container forward to trigger the dose using the portafilter dose button. It also serves the purpose of stabilising the load cells in the scale so you get an accurate reading. The 75ml Decor container has a lip that perfectly fits any VST or 58mm basket. Once inverted you could save $62.35 and simply shake it there, or do a modified “Holdswirl”. Palm tap, collapse if needed, tamp, then pull. As soon as you’ve dosed your shot just return the container to the scale, ensure it’s tared off, and start the next dose. Beside the grinder I have an 8oz cup, a Mazzer conical burr fitted in the top, and a parfait teaspoon inside that. I discard grinds into the container if the grinder over-doses, and top up my dose from the container if it under-doses.

I aim for a 20.1g target, with a 0.1g variance. This may seem tight, but I don’t manually tamp, I have a Puqpress. This saves me enough time to be diligent on my dose. But even when I was using a 58.5 Pullman tamp, I had a target of 20.2g, and only a 0.2g variance. All the data I have so far points to a 0.2g variance over or under the recommended VST basket dose as not having a significant effect on extraction yields, time of the shot, or physical yield of the shot. I’m sure I could push that variance out even further to see where the ceiling is, but this works for my workflow so I have no real reason to push. Also having no discernible effect is the fact I top up my dose from the grinds bin. I’m never topping up more than half a gram at most, so it seems in this case that as long as you stick within the target range, with a sensible variance, you’ll hit your target extraction yield – even accounting for “old” grinds topping up to your target dose.

(#Pro-tip: what the fuck is the Mazzer conical burr for? The steel alloy they are made from does a magnificent job of discharging static. Why do you get static? That’s a whole different topic, but weighing at the grinder and dosing into a plastic container, while also keeping the burrs and chamber clean regularly, and something I’m sure that has to do with touching the clump crusher, along with some weird voodoo shit or possible wrong doings in a past life, all result in a metric fuck-tonne of static on any given day. In a high-volume environment the Ross Droplet Technique isn’t really viable – this however is. In practice, after dosing into the portafilter, I invert the container, give it a little tap to dislodge any grinds that are stuck, move it over to the Mazzer burr, then brush the bottom of it over the burr for a second or two, before back onto the scale and starting the next dose. That sounds far more complicated than it is – but believe me, it’s quick, and it stops static dead)

Symphony of the Mythos

Each morning I set the volumetrics on my GB5, using a scale to hit my target ratio – not a shot glass, or other form of volume measurement. Yesterday’s leftover beans get turned into cold press (or cold brew if that’s what we’re calling it) as I want a “fresh” reading for the volumetrics, based on the roast date I’m using that day. On a Monday it takes a while for the grinder to “settle in”, as I’ve had it turned off for the weekend. So throughout the week I leave it on, as it takes 24 hours for it to reach temperature equilibrium, according to Nuova Simonelli USA. Kegman Kipp, fellow Mythos owner and receiver of personally signed Christmas cards from Mr Schomer himself, spent 14 days with his element unplugged and fine tuning his shots as much as possible, with none coming close to how day 15 tasted with the element on for 14 hours. Leave it on overnight if you can – you should taste the difference.

The ‘Symphony” here relates to the complex interaction of all of these factors together, and how everything I’ve written above leads to one thing you need to do – watch your dose weight. Gas dissipation and batch changes in beans will mean the timed dose will change each day. But it doesn’t take long to dial in a time that comes close enough to hitting your target dose, and the Mythos tends to dance around this target within half a gram or so. From here any adjustments in dose from or to the grinds bin are minimal. Once I have a grinding time I’m happy with, I turn the numbered grind dial to zero (you knew it moved right? Well if you don’t know now you know) then start pulling shots.

Changing the grind now is simply a matter of watching the weight on the scale and how that relates to the time for the volumetrics. If weight goes down dramatically – over half a gram – I coarsen the grind to; if it starts dosing too high I fine up the grind. With practice you realise you don’t need to ‘test’ a shot to see if your time is too fast or slow, you just trust the weight. You should always be hitting your target time, by only adjusting your target weight through grind changes.

You could compensate for the change in weight by simply upping or lowering your timed dose. More or less time grinding means more or less grinds in the cup or basket, and no need to fuck about with a grinds cup to top up or dump into. But that’s ignoring the evidence at hand. Say your dose weighed 19.5g – you want 20g. So you adjust the time and dose your next shot. This shot, now at your target dose through changing the dose time, has pulled in 35 seconds. That was always going to happen, only now you change the grind to compensate, and you get a dose that is over by a gram. Not only have you upped your dose, you’re coarsened the grind by widening the aperture between burrs, allowing more beans into the burrs, and out into your cup or basket. The problem is compounded, and now you have a 21.5g dose, you’re tipping grinds out to compensate, and more importantly – you’re wasting precious time. This is high volume remember? We need this to be a production line. So start paying attention to evidence. A significant decrease or increase in dose weight, while keeping grinder time constant, does correlate to fineness or coarseness of your grind, which logically carries over to a fast or slow shot time.

Ah fuck, but only if you have your beans covering the exit chute of the hopper. Which is difficult at the end of your busy rush when you know during the afternoon you’ll be lucky to get through two kilos, let alone one. What I’ve found is the lower the beans in the hopper the lower the dose weight is, so as the bean level goes down I compensate by gradually extending the timed dose, and watching my shot times instead for an indication of where my grind setting should be.

That alone should be the clearest indicator that the hard part here is making sure you have everything else that can be effecting that weight under control, or you’re at least factoring it in. This is the game you play each day behind the machine – keeping variables constant while watching the dose weight. Weighing at the grinder, for me at least, seems to offer a stronger cognitive link between those variables – hopper weight, roast date, or batch changes – and all those small, imperceptible differences in humidity, a slightly off tamp, 0.3 grams off this time, 0.2 grams too high the next, all those things that lead to you not quite hitting your target time or yield. A symphony is definitely no joke, and that’s the challenge the Mythos presents.

But that’s pretty much it. Everything else you have to worry about – bean management, tools, cleanliness – that’s all basic espresso management. For the Mythos I’d just dial down your pressure to ~6 Bars, keep it clean and the burrs aligned, left on as often as possible, and weigh your dose accurately. As far as “Barista Friendliness” goes the Mythos is fucking great. To be able to dial in the time of the dose and the grind itself from a forward facing user interface is incredibly helpful while you’re moving fast under pressure. If our volume allowed for it, I used to think I’d use an EK43 any day. But the more I’ve come to use the Mythos alongside the EK, the more I’ve come to appreciate the unique flavour it gives my espresso – usage idiosyncrasies be damned. It’s not better than the EK43, and the EK43 is not better than the Mythos. They both fit a need, and both produce espresso that results in incredibly flavour. For me, the Mythos is a high volume beast, and that suits my purpose. We used to have 90 gram retention problems, bimodal bullshit from conical burrs, clumps like clay, and a grind change mechanism that required at times both hands just to turn it one fucking degree – and that’s if your hands didn’t burn on the neck. The Mythos was clearly made by baristas for baristas, and I find it invaluable to remember how far removed it is from where we’ve come, and how good we have it right now.

Michael Cameron

(Send me your views, trolls, spelling or grammar corrections, and random hearting on twitter; you can find me here. Alternatively you can join the conversation on the Barista Hustle Slack, or the Barista Hustle Facebook page – I’d love to post my Mythos alignment pics for the fifth time. A nine-stack rosetta pour is nailed every time you double-tap over on Instagram).

This Low Pressure Lark

“If I have seen further, it is by standing on the shoulders of giants” (Isaac Newton, 1676)

I can only imagine how it would feel to find that perfect shirt to wear out. And having found that shirt, ironed it, hailed a cab, headed into town, you turn around and see that shirt. Your shirt, but not yours, on someone else, and not you. Your shirt. But better.

I’m pretty sure it would be similar to how it’d feel to write my post last week, then find this post by Maxwell Colonna-Smalls … which led to this post by Matt North (literally titled “Marginal Gains – Maximising Extraction through Flow Rate and Pressure”) … which in turn cycled back to Maxwell’s post covering 15g basket – which of course included discussion of flow rate and low pump pressure. Let’s not forget to mention posts here and here by Matt Perger also mentioning pump pressure and flow rate. It might be a similar feeling. Or maybe I’m just overstating how shitty it felt to think I’d stumbled upon a Great Truth of Espresso, only to realise I was simply standing tall on the shoulders of others. I spent a sentence making analogies to waterfalls – Maxwell wrote 1000 words, and he had pictures.

Truthfully though in the back of my mind, when following this thread of low pressure I always felt I was playing catch up. Maxwell, both Matt’s, and countless others, had caught up already to the idea of how physics form the basis of the modern espresso shot. I’m still attempting to catch up, and in doing so I think it’s instructive to see how this style of espresso differs when contrasted with the traditional 9 bar shot. So let’s start with that – and if anyone else out there has already covered this, consider this “borrowing” the concept …

Making espresso with 9 bars of pressure means we need to grind fine, with the fineness of the grind itself creating resistance to the pressurised water. This resistance means the water has to work incredibly hard to move through the coffee and get to the other side, out of the filter basket holes, to where it wants to go. On it’s way, this pressurised hot water extracts flavour from the coffee – and therein lies the whole premise of high pressure extractions. The fineness of the grind also enables a larger surface area of the coffee to be exposed, allowing for a fast extraction typically around thirty seconds. But the high pressure creates some problems that need to be worked around through both equipment and technique.

The first problem is channelling. Everyone should have learned back in barista school that water is lazy. Say it after me: “water follows the path of least resistance”. So distribution of the ground coffee is crucial to ensure there are no weak spots or unevenly distributed pockets of coffee or air within the basket. Otherwise high pressure water will simply gush through the puck like a water blaster at a bucket of sand. Along with the actual distribution of the coffee, tamping is equally important. Tamping unevenly will create the same problem as distributing the coffee unevenly – looking sideways at the puck, there will be one side “thinner” than the rest, and conversely an opposing larger side. Water will take longer to travel through the larger side and less to travel through the thinner side, leading to an uneven extraction. The tamp also needs to be fitted to the edge of the basket. A tamp that’s short of reaching the edges will allow another avenue for water to channel through the gap created.

The physical act of tamping presents problems as well. Resistance to pressurised water does not just come from the fineness of the grind, but also with how compact the grinds are themselves. Traditionally we were taught the “thirty pounds of pressure rule”, so we tamp hard and as consistently as possible to around this level to compact the grinds to an even density. But however hard we tamp, it needs to be consistent, as the fineness or coarseness of the grind, along with how hard we tamp, all contribute to flow rate through the puck. A consistent tamp should correlate to a consistent flow rate, or so our 9 bar theory says. But this doesn’t take into account how this density actually plays out, with the physics involved instead distributing the energy towards the middle of the puck under tamp pressure, not evenly throughout the puck. Effectively the harder you tamp, the denser the middle of the puck gets, but not both the top and the bottom.

Also with 9 bars of pressure water moves quickly, which doesn’t allow much time for the water to do it’s job of extracting flavour from the coffee. The temperature also combines to speed up flow. With the boiler set to between 93 and sometimes up to 96 degrees celsius at the group head, this temperature lessens resistance as the heat increases solubility. Our fine grind should balance out both pressure and heat to allow the water to reach some kind of temperature and diffusional  equilibrium with the coffee, but perhaps not enough time. Luckily the pressurised water compresses the puck towards the end of the shot, with this compaction increasing resistance. The pressurised water also blasts the fines – the little bits, or little guys that form part of the particle distribution of the grinds themselves – towards the bottom of the basket, clogging up the filter holes, in a process sometimes known as“fines migration”. Not enough fines migrate so nothing can get through, but enough to aid resistance.

Basic 9 bar extractions are simple enough to understand in theory, but putting it into practice there are so many points of possible failure there – all going back to the fact that it’s highly pressurised water blasting though a small puck of coffee in a tightly confined space. I mean that’s how we get espresso, but repeatability is such an elusive outcome here. So taking a different tact, let’s actually list what needs to happen to get an even extraction, after we grind:

  1. Evenly distribute the coffee in the basket.
  2. Tamp the grinds down in a level manner.
  3. Tamp the grinds down in a level manner, to an even density.
  4. Tamp the grinds down in a level manner, to an even density, with a fitted tamp.
  5. Tamp the grinds down in a level manner, to an even density, with a fitted tamp, one coffee after another.

Now look at what needs to happen while we actually pull the shot:

  1. Our grinds have been evenly distributed, tamped down in a level manner, to an even density, with a fitted tamp, consistently one shot after another.
  2. Enough fines then need to migrate to the bottom of the basket, in a consistent manner shot after shot, to slow down the flow rate to enable temperature and diffusional equilibrium.
  3. The puck also needs to compact at the right time, to the right amount, in a consistent manner shot after shot, to also help in slowing down flow rate allowing temperature and diffusional equilibrium.

For shits and giggles, what about looking at what needs to happen before we grind or pull the shot? In the hopper here’s what we need:

  1. Your beans are roasted to an adequate development and roast level.
  2. Your beans were stored in a bag with a one-way valve.
  3. Your beans were sufficiently degassed, or ‘aged”.
  4. Your beans are from the same roast date, and better yet, the same batch.
  5. You have enough beans in the hopper to defeat the “popcorn effect” (I’ve yet to find an auger that manages this consistently).

What about the grinder?

  1. Your burrs are not blunt – better yet, cleaned regularly.
  2. Shit, your entire burr carrier chamber is cleaned regularly.
  3. The burrs themselves are aligned correctly (An Ahab action if ever there were one).
  4. Heat has been managed as effectively as possible (I could go on about heat, and how it affects variability, but for now I’ll keep that conversation for another time).

All your shots are extracted from your machine, so what about that?

  1. Your machine is clean. And I mean clean – factory fresh clean. Any part of the machine that has been in contact with the coffee has been cleaned with coffee detergent, then cleaned with fresh, hot water.
  2. Your seals are functional.
  3. Your screens are functional.
  4. Your brew water temperature is consistent.
  5. You’re using VST baskets. (And stop it. Just fucking stop it. VST baskets or piss off. Not IMS baskets. Not La Marzocco Precision baskets. Not the stock standard shit-ass sucky things that get packaged up with your home espresso machine or whatever they give to you with your $25k Slayer. You’re using VST baskets. No one in the industry has put more research and development into baskets than Vince Fidele. They have a proven track record, tried and tested, repeatedly – you’re using VST baskets).

What you have listed here are twenty-two potential points of failure for an even extraction – give me an hour, an espresso, a glass of water, and a captive audience, and I could double or triple that amount. And even with what I have listed, I know damn well half of you reading this are thinking “what about this or what about that?”

You see, if you get none of this right, if none or only some of these variables are lined up, you have no hope of getting a consistent shot. How that shot performs informs how you approach grind changes. This should be self-evident to any barista who’s spent time on the line. If none of these variables are accounted for, or interpreted in the wrong way, you will most certainly be lost in the noise. Tamp not level, shot gushes out, change the grind to fine – next shot chokes. Tamp down too hard, shot slows down, change the grind to coarse – next shot gushes. Your tamp is not fitted, temperature inconsistent, burrs are blunt, not using VST baskets, beans too young, not enough in the hopper – you’ve got no fucking idea – so enter stage left the Great Coffee Superstitions: “It’s a Tuesday, shots always suck on a Tuesday”, “Yeah it’s quite humid today, maybe close a window”, “Do these beans look darker? I think they roasted this batch a little darker”, “This machine is totally broken, did someone fuck with the volumetrics? And all the way to my all time favourite: *shrugs shoulders* “Just one of those days, you know? Coffee huh? it’s a motherfucker”.

All variables funnel out from that shot, built upon one another, after one another. Look at it as an even extraction being on one side of a window, you on the other, and all those variables muddying your view. It’s only when we clear the mud that we can see an even extraction.

You can clear some mud easily enough. You can thoroughly clean your machine – and that should be part of your daily routine. You can clean your burrs regularly, keep a record of how many kilos have been through them, vacuum it out regularly, align them with shims. You can get consistently roasted beans. Keep your hopper filled. You can buy VST baskets, a fitted tamp, have your machine serviced regularly. None of this is too hard, or too much to get done. These are variables you can control, and should be controlling.

Controlling your technique though, making it repeatable? And this after attempting to deal with a particle size distribution of your grinder that you cannot change? 9 bars of pressure, blasting though your puck, with the only thing standing between a 20% extraction and a ruined shot being you, this Rube Goldberg technique and workflow, and the physical limitations of your grinder? That’s hard. But that’s how we do it, because 9 bars of pressure is how we get shit done round here.

But Maxwell discovered 6 bars of pressure enabled sweet extractions, with little to no variability. Matt North moved down to 6 bars and discovered his average extraction went up to 21.28% – “In fact, extractions below 21% are now in the minority rather than the normal occurrence”. Matt Perger, when referencing the difference in pressure from the top of the basket and the bottom of the basket – “I love even extractions. So why not lower pressures?”

Exactly. Why not lower pressures? And if you do lower pressure, what difference is there compared to 9 bars of pressure? I tried answering this in my previous post, but I think in trying to broadly outline my argument, I messed up my delivery. I need to simplify it. So here’s another attempt:

First and foremost, a low pressure means a low flow of water. This enables a number of things, either happening concurrently or consecutively:

  1. Low flow of water allows for a slow infusion of water into the puck. This slow infusion mitigates uneven particle size distribution, as rather than blasting the little bits to the bottom of the puck and blocking up the filter holes, the natural expansion of the beans as they saturate means they expand “in place”.
  2. Any uneven distribution of force when tamping is mitigated, as rather than have these high or low density areas either allowing water through or blocking water, they instead follow the even same expansion upon contact with the water.
  3. Steps 1 and 2 mean that once the puck has fully saturated and the pressure built to whatever you’ve set, this pressure spreads in an omnidirectional manner evenly throughout the entire puck.
  4. The slow flow of water also enables the water to reach temperature equilibrium with the coffee within a timeframe that allows for even extraction for the particle size distribution of your grinder.
  5. Not only does it allow for temperature equilibrium, but also diffusional equilibrium between the water and the coffee within a set timeframe, again allowing for even extraction.

The variability of the particle size distribution of your grinder, or the set mode of that distribution, has been mitigated by low pump pressure rather than exposed by high pressure. The variability of your tamping technique has been mitigated by low pump pressure rather than exposed by high pressure. The variability of your tamp pressure has been mitigated by low pump pressure rather than exposed by high pressure. Is this starting to make sense? What this logically leads to is variability between your shots plummeting, while extraction yields go up.

This has an immediate and exponential effect. With a significant amount of mud cleared from your window, machine and grinder cleanliness, bean quality and management, technique, grind changes – all this sharply comes into focus. You tighten up, with a clearer vision of what needs to be tightened up, all without any background noise. It’s a virtuous cycle, all caused by one thing – less variability in your shots facilitated by low pressure.

Less variability will not come however without some adjustments and experimentation to your technique, workflow, and recipes:

  1. Any calcium build-up in your machine that 9 bar pressurised water will have blasted through, now creates a barrier low pressure water will have a harder path to pass through. Keep an eye on flow rate – you may get an earlier-than-before signal that it’s time to service your machine. Have a look at your filtration system also while you’ve got the technician there.
  2. Distribution is still incredibly important. You need to be palm-tapping at least, and collapsing if your dose is still too high in the basket. The finer you grind the easier this distribution becomes.
  3. If your tamp is not fitted to the basket, the slower flow rate will allow the water more time to channel through the gap caused by the under-sized tamp. This runs kind of counter-intuitively against the idea the grinds saturate then expand “in place”, I can only theorise that perhaps the water channels too quickly through the gap before the puck is saturated enough. Either way, swapping out a 58.4mm and above tamp for a 58mm tamp had dire effects on extraction yields. At this point you really should have at least a 58.4mm tamp.
  4. Your brew water temperature will need to come down to compensate for the extended dwell time caused by the slow flow rate.
  5. This will need to be calibrated to how long you pull the shot for, which in turn will affect your yield. If your grind is kept at the same grind setting as your 9 bar shots, you’ll initially want to go coarser to allow water to actually flow through the puck – the slower flow rate caused by low pressure means the smaller grind size increases resistance.
  6. And this will cycle back to grind size and tamp pressure …

Which leads to two remaining questions. It may be a lark but you can go low, with 6 bars at least allowing entry to the club. But once inside you quickly realise it’s now about how fine you grind and how hard – or how light – you tamp. One allows less dispersion in grind particle size, the other allows that smaller dispersion in the first place. Both lead to even less variability with high extraction yields that are easier to obtain. All other variables can be worked out in a systematic manner, but these final two are rather tricky when thinking of repeatability and consistency. “How fine you grind and how hard or light you tamp” may not make too great of a title, but once you go low you quickly realise that’s a question in need of an answer.

Michael Cameron

(You can join the conversation over on the Barista Hustle Slack, or on the Barista Hustle Facebook page. Alternatively feel free to lodge your dissent or agreement with me in 140 characters or less over on twitter; you can find me here. As always an abandoned puppy finds a new home every time you double – tap over on Instagram).

How Low Can You Go?

“Most of the world’s observables are easily described by a simple set of physical laws. But, as we begin to focus on more detail we quickly realise that our simple laws are not refined enough to describe the more complex interactions. It is these complex ideas that frequently show up in a cup of coffee.”  (Christopher Hendon, 2016)

Over on the Barista Hustle Facebook page, there’s been some discussion surrounding flow rate and water debit. I was going to reply there, but a 1900 word comment to a post may have been a little over the top … Instead I’m going to lay some of my own thoughts out here. So settle back in your chair then and get comfortable – I’ve had a lot to think about  …

I liked the explanation given on the difference between “water debit” and “flow rate” over on the post in question (have you signed up yet? Go do it!) – water debit being “the measured flow rate of water out of an empty portafilter with the pump on”, flow rate “the measured flow rate of espresso out of the portafilter during a shot”.  Pump pressure was left out of the initial explanation but I feel it’s an important contributing factor – you can’t talk about water debit without talking about pump pressure. However they’re easily confused, or misinterpreted.

When it comes to pump pressure I like going with the analogy of a waterfall, with “flow rate”, or “water debit” (which I’ll be calling it) being the amount of water that rushes over the edge of the cliff, within a set time. How hard the water hits the lake or river below is what I’d call pump pressure. That second definition there is important when thinking of how we measure “flow rate” during a running shot. It’s not through measuring how many mills in how many seconds as we do with water debit. Rather we measure that output in grams as the shot yield – a ratio to the dry dose also measured in grams, correlated to the time it took for the shot to reach the yield we wanted.

I think it’s important to see that water debit is only important up to when it hits the puck. At that point, with a fine enough grind, it would cease to flow based on the resistance it’s met. It’s the pump pressure that picks up the baton and starts moving the water through the puck. Restrictors on your machine (literally restricting the flow of water out of the group) are one of the few options available to slow down water debit. Until you do install restrictors it’s best to see water debit as a set variable you need to work with.

It’s worth pointing out that water debit and pump pressure both lie, and operate on, different spectrums: slow to fast water debit, and low to high pump pressure. So ignore pressure profiling and pre-infusion for a moment, and instead focus on restrictors slowing down water debit, and your pump pressure being lowered. So now we have slow water debit and low pump pressure. This is where things get a little hairy because we need to look over to the side at our grinder.

The grinder’s particle distribution is set – a gross simplification but this being the mix of small bits of coffee and big bits of coffee that result when the beans hit the burrs. I know – very scientific. Heat will mess with it, but until grinder technology definitively deals with that issue, we need to look at grinder particle distribution as another set variable we cannot change. Pump pressure, a variable we can change and fix in place, needs to now be looked as accommodating the set variables of particle distribution and water debit. As far as grinders go embrace it’s particle size distribution, and hope that at the very least whatever that distribution is, it produces it consistently. If you know your particle distribution creates a large number of fines (looking at you EK43) or a large number of boulders/intruders (hey Mythos One) then we can start slowly pulling all this together and connect the dots.

So lots of small bits and not so many big bits mean you dial in your shot based on the extraction of the small bits. You don’t worry about the big bits because at best within the time frame it takes to extract the small bits, there hasn’t been enough time to extract anything from the big bits. At worst the even extraction of the small bits drowns out the under extraction of the big bits. With lots of big bits, you dial in your extraction based on the big bits, not worrying about the small bits as the over-extraction of the small bits is drowned out by the even extraction of the big bits. It can be a bit of a head scratcher but once you grasp the concept you realise what we’re trying to do is optimise whatever majority of particle size we have – either small bits or big bits.

Still with me? The particle size also has important implications for distribution in the basket. Now we need to go up a level from particle size distribution, and focus instead on what we all know – grind aperture, or how fine/coarse your grind is. A finer grind is less size disperse – so more small bits, less big bits. Less difference in size between those small bits and big bits has an important implication for water debit and pump pressure, by placing less importance on initial distribution in the basket, and tamp pressure compacting the puck.

So grind fine and distribute with palm tapping and collapsing. This is more to prevent initial weaknesses in the puck the water debit may expose (especially if it’s fast) which the pump pressure will exploit later when it kicks in (especially if it’s high). Next, when it comes to tamping you need to look away from the idea of “maximum density” as something we wish to achieve, and instead focus on “maximum amount of force required to distribute energy evenly throughout the puck”. This is an important distinction. You have big bits and small bits in the puck – tamping hard will not move the big bits past the small bits, no matter what the force is. While with some grinders there are by far more small bits than big bits (thereby mitigating this factor, and hey again EK43) a heavy tamp also runs the risk of squishing the density together in the middle of the puck, and not at the top or the bottom. Variable pressure will simply move these “high density” or “centralised energy” points around to different parts of the puck. Once you have reached full pressure – be that low or high – the great equalising force of pressurised water can only be exerted throughout the puck based on either the initial evenness of tamp pressure energy distribution, or worse the variations in that distribution. We need a different solution.

If you’re still with me, thanks for the company and your perseverance, as this is where I finally get to the point. Low water debit along with low pump pressure is important because it eliminates both particle distribution and tamp pressure as variables, or at least lessens any negative impact they may have. Low water debit cancels out any imperfections in the puck as it’s initially presented to the water, meaning when the low pump pressure kicks in, it will evenly begin saturating the puck. If you can control the tamp pressure and evenly distribute energy throughout the entire puck, then the low pump pressure will also evenly start passing through the puck, enabling an immersion style of brewing. The slow and even saturation of the puck will promote even expansion of the coffee, either mitigating variable tamp pressure, and/or furthering even extraction. The slow contact time promoted by low pressure water enables the entire puck to reach temperature and diffusional equilibrium between the brew water temperature and grinds. Given the nature of modern espresso machines, that temperature remains constant throughout the entire extraction as the column of water passes through the puck. Once the puck is entirely saturated flow will begin speeding up due to conductivity.

So with a fully saturated puck – whereby tamp pressure energy variability has been mitigated or eliminated, and with the puck also reaching temperature and diffusional equilibrium – you can grind finer to compensate for what would have been a faster flow at a coarser grind. A finer grind, and with that less dispersion in particle size, means you can now dial in an optimum time for how much contact the small bits/big bits ratio of coffee should have with the temperature controlled water. You dial in how much time this needs by measuring output of the shot by weight. Shot weight is varied by grind size. Triangulate your fixed dose to this shot time and beverage weight, and dial in your brew temperature to compensate for the increased contact time the coffee has with the water. You’re now making the low pump pressure work with the limitations you have, rather than high pump pressure work against those limitations.

High pump pressure was preferable once as it was reasoned that by grinding fine you create resistance to the initial water debit and the high pump pressure. It was this resistance that would work to extract flavour from the coffee. Along with this pressurised “hard work” it would also blast the small bits to the bottom of the basket clogging the holes up, thereby artificially slowing down water debit, and the ensuing flow rate of espresso. It was this clogging process along with the fine grind resistance of the entire puck that enabled the temperature of the water to have enough contact time with the coffee. But when viewed through the lens of particle size distribution, actual coffee distribution in the basket, and even distribution of force throughout the puck, you can start to see how this theoretical basis works against the physical realities of your equipment and the over-reliance this has on technique being consistent.  Again – we need a different solution.

So this is worth repeating – with a slow water debit and low pump pressure you can target the small bits for optimum or maximum extraction, while ignoring the big bits. Alternatively you can target the big bits, and hope the small bits will be drowned out by the big bits. In this way you can ignore the variables you can’t change, tweak some of the variables you can change, and fix in place the remaining variables that you can change, but probably shouldn’t. You achieve all of this by slowing down water debit, lowering pump pressure, grinding fine, and focusing on a tamping technique whose energy produces an even distribution of force throughout the puck.

None of this is really new, it’s part of basic espresso theory we’ve all been taught since the days of David Schomer,”Espresso Coffee: Professional Techniques”, and Illy “Espresso Coffee, The Science of Coffee”. What is new is our understanding of the physics involved, and for that we need a new paradigm of thinking. 9 bars worked when we thought we had to make the grinder fit the espresso machine. I think we need to now look at the espresso machine fitting the grinder, and an integral part of that is water debit – but more importantly, pump pressure. And this begs a parting question: in the immortal words of Chuck D, “how low can you go?”.

Michael Cameron

 

(I hate comments under articles – it’s a personal thing – so they’re closed. Instead, make sure you join the conversation on the Barista Hustle Slack, or the Barista Hustle Facebook group. If you feel like perusing my past conversations with the Optus twitter support team before engaging in 140 characters, you can find me under @strivefortone. Alternatively, feed my inner narcissist and double-tap that shit all over the show while admiring my #epichashtaggame on Instagram – an angel gets it’s wings every time I get a like … )

 

Introductions

Cooking has always been a hobby for me, something I do at home, not something ever done professionally. I once auditioned for Masterchef Australia, got through to the final day of auditions before the final 1000 would be flown to Melbourne. I cooked crispy skin duck breast, with duck fat pan roasted potatoes, with an asian inspired red wine reduction. I practised that dish so much that in the end, with 45 minutes allotted cooking time, I was sipping on the remainders of my red wine while letting my duck rest – still with five minutes to spare.

When they called me and said that unfortunately I didn’t fit in with how they wanted this season’s “mix of contestants” to be, I smiled, nodded, and said I understand. Because I did understand. Waiting around for my heat to start, listening to the other contestants auditioning, I was struck by how little I gave a fuck about the minute details of my dish, or any dish for that matter. One person had spent the night before foraging for mushrooms. In a public park. In the heart of the Brisbane CBD. I was never going to be like that – cooking was a hobby, a passion, not something I realised then that I wanted to pursue as a career.

What all the judges did note however, and what has stuck with me, is how entertaining they found my application letter. If you’ve read any of my previous posts, then that was pretty much how I wrote my application. I took the piss, but I was serious at the same time. While reading over my application he had in front of him during my third and final interview that day, one of the judges remarked how far I would go if I was to instead write about the food industry just like I wrote my application. I knew then I wasn’t in, but those words have stuck with me.

I may not want to cook for a living, but I do make coffee as an occupation. I manage a busy inner-city espresso shop, that turns over a fairly large volume of coffee. I’ve been making coffee ever since I started full time in hospitality, a little over 17 years ago. I wouldn’t say I’m passionate about it, I think that is the wrong word. Rather I have a desire to make coffee to the best of my ability, and that desire has never wavered. In pursuit of fulfilling that desire I have continuously refined my knowledge, technique, and general coffee know-how, each year discovering new facets, areas, and dark corners I can shine a light on and learn more from.

With this idea in mind, it was a revelation discovering Matt Perger’s “Barista Hustle” website and subsequent weekly email newsletter. It felt like a giant leap forward in learning how to make coffee better, outshone only by the opening to the public of his private Slack group, a group made up of coffee professionals from World Barista Champions, renowned home enthusiasts, and industry veterans. Creating a Facebook group only increased the variety of conversations and revelations surrounding making great coffee.

It has been a conversation I have been immensely proud to have been a part of, and help contribute to, and one I hope to continue with here. Both the Slack group and Facebook page are not really conducive to 1500 word essays expanding on my thoughts about coffee, and considering I continue to keep this site running, I feel now is the time to begin contributing again. I’m not saying I know all the answers on how to make great coffee, but I do have over a decade and a half’s worth of experience in standing behind the grinder and pumping out shots. This had led me to a number of views that I hope to express here. I can only hope you find them at the least entertaining, with some interest attached …

I will not be keeping the comment pages open here. Instead, I urge you to join the conversation happening on the Barista Hustle Slack group, sign up to Matt Perger’s Barista Hustle newsletter, and head over to the Barista Hustle Facebook page. I look forward to continuing any conversations further through the Slack group or Facebook page. By way of introduction, my name is Michael Cameron, and I make coffee.

“The domain name … is about to expire.”

I was going to write again next week. Something witty. With a recipe. Reminisce maybe and tell a story. I like telling stories. About when I grew up, where I grew up, how I grew up – all stories of my youth, of my past, of what I was way back when. I’d add a recipe at the bottom. I like cooking, I’m good at it. The food would taste good, the recipe tell it’s own story. So next week I was going to write. A witty story from the past. With a recipe at the bottom.

Then an email arrived. “The domain name for your blog strivefortone.com is about to expire soon …”. I thought to myself the week had surely flown by. But it had been a year. And I still hadn’t written. No wit, no tales, no no measuring with kitchen scales.

I got fired that year. For being drunk. Not at work that is, I wasn’t quite that functional an alcoholic yet. I wasn’t even sure if I was an alcoholic then. But I’d come home from work, sit on the air-con unit outside, smoke cigarettes, and drink beer until Big Bro came home. Then we’d get a burger, sit on his couch, and watch TV. I’d smoke some more cigarettes and have a few more beers, and then I’d turn up to work, after my staff had started, and sit at my desk eating muesli from a takeaway cup and wonder why a few months later I was told my employment was being terminated. I actually laughed when I was told. I thought it was a joke. I remember being angry, walking out, my boss shaking my hand then looking down at his feet. “Yeah sorry mate, but I need your key too.” Should have been plenty of time after that to write a witty story. Even just cook. But I didn’t. I drank beer and smoked cigarettes and never wrote a witty word and never planned a recipe for the bottom.

Two more jobs? Three more? There was the suburban specialty coffee shop with the ex-army boss and his wife. Working 25 hours a week and cooking again I started getting some semblance of shit together. I made some beautiful coffee there. And calmed down a little. Breaking up with my now ex-fiance had clearly, at this point in self-reflection, had me go just a little fucked up. Sitting at home on New Years Eve smashing back the best part of a 24 box of beer and staring up at fireworks in the sky can bring about it’s own special brand of insight. Time to get my shit together. I think I might be drinking too much. Coughing, then staring down at my yellowed fingers I thought it might pay to add smoking to that list as well. And procrastination. There was way too much of that going around.

“The domain name for your blog …” Fuck had it been a year already? Two years and no words and I’m paying this $34 because I’m sure I’ll start writing again I just can’t seem to get past this block but I got ideas man. I got recipes. After this beer. After this cigarette. I love cooking. Just not so much that I want to keep writing about it. I want to pivot, turn to something else that I’m confident in. Like coffee. I want to write about coffee. But I’ve got to stop drinking. Got to stop smoking. Got to start writing. This is getting embarrassing. It’s been over three years now. And I haven’t written a witty story yet. And I know now there won’t be a recipe at the bottom.

“The domain name for your blog strivefortone.com is about to expire soon …” 

She said “hey”. Dechen said hey. I didn’t even know how to pronounce that name. Her profile looked cute. “Looking for a partner in crime” it said. I could get criminal I guess. But I didn’t even know what she looked like. All her profile pictures were weird ones of her in a bumper car or dressed up for Day of the Dead. We messaged back and forth. A day later we were Facetiming. I told her a witty story. She laughed and a week later we had coffee. A week after that we made pasta, kneading the dough and rolling it out. We made pesto together, we ate together, laughed and joked together. She wasn’t ready though. Not yet. Her wall was too high and I couldn’t climb over.
But brick walls are there for a reason. There to prove how much you want something. But it wasn’t like I “wanted” her. I just couldn’t stop thinking about her. So we tried again. And she said no again. And then I tried again. And she said no once more. I kept climbing but I couldn’t reach the top.

I got a tattoo. I grew a beard. I gave up smoking then realised I’d have to give up drinking too. I played ukulele with her on her couch, outside on her balcony. I listened while she spoke of her flatmate. I counselled her on how to deal with him. I sold her my iPad. Taught her how to use it though we both knew she knew how the damn thing worked. We watched Game of Thrones and once I brought around an entire picnic, with three different styles of pork, and I slept on her couch because I went well overboard with the food and it scared the shit out of her. She wasn’t ready yet. Not yet.

Then she went to Italy, and we spoke some more, and we talked in the morning then said good night before we slept. We were nine hours apart and closer than we had ever been before and when she returned home, that day in January, I finished work early, caught a taxi to her house, and kissed her full on the lips for the first time in forever.

A year later I proposed. Six months more and we were married. Four months later and I got an email.

“The domain name for your blog strivefortone.com is about to expire soon …” 

And I thought to myself “fuck this it’s time to write.”

 

(My) Teriyaki Chicken

Twin Bro

We’re young, maybe three, on an adventure in the backyard. The wooden shed at the back is always good to explore. We spot some cans on a shelf, out of our reach. We’re inquisitive, maybe just nosy; we want to find out what’s in those cans. I grab a stick, or maybe Twin Bro does, and we prod at the shelf inching the cans towards us. After a short time gravity takes over and the cans tip on their side; paint cascades down over us. Drenched in paint and crying in unison, we sprint back out into the yard.

Ma spends the afternoon there with us, hose in one hand, scrubbing brush in the other.

It’s the middle of the night and Twin Bro has spiders in the bed. He wakes us up, crying. I turn on the light and Big Bro checks under his sheets. The spiders are gone and we go back to sleep. It’s an hour later, and the spiders are back. Big Bro turns on the light and I check under his sheets. The spiders are gone. Took months for the bastards to finally leave him alone.

Out in the sunroom, windows on all sides, it’s the middle of summer and flies are everywhere. We’re four years old, maybe five. The crashing sound summons Ma, who discovers us swatting the flies against the windows. Using the buckle of a belt. Her timely intervention saves the windows, but three flies do not survive.

We’re eight years old, outside our fathers flat. It’s the school holidays. After three days we’ve watched four movies about American Indians, have broken the plastic firing submarine for the huge battleships game, worked an hour with dad at work and been paid $10 each, and had homemade fries for dinner each night. Dads asleep on the couch, snoring. Big Bro’s watching TV, and Twin Bro and I are bored. We go outside to explore.

Outside the flat are overgrown flowerbeds and broken concrete. An old, worn down wooden shed is at the back. Inside we discover a bulging milk carton on the dusty concrete. Our eyes triangulate between the milk carton, a nearby rock and each other. We nod quietly, bend down each side of the rock, lift it up together, and waddle over to the carton. We’re smiling now, as we heave the rock into the air, quickly take a step back and cover our ears, excited at the popping sound that’s sure to come.

It doesn’t pop. It squelches then bursts, instantly drenching us in slimy, cream-coloured, rancid old milk. The smell assaults us, we yell, we scream, we sprint up the stairs into the flat, straight for the bathroom. The shower is flung on; clothes and all we climb in, giggling, laughing, and giggling again. We woke up dad; he pokes his head round the door, starts shaking it. We just laugh and giggle some more, washing the milk off.

It’s Mothers Day, we’re ten years old, outside in the backyard playing soccer. Big Bro goes to kick off, and when his foot hits the ball, an earthquake hits our town. It’s massive. Ma’s on the porch; it’s wobbling in unison with the rumbling quake. She’s yelling for us to get inside. Twin Bro and I race into the kitchen, diving under the table. Ma’s bottle collection, lined along shelving across the living room walls, is crashing to the floor, a carpet of shattered glass. Big Bro is still outside, racing around the house, yelling and laughing, falling over and getting up, manic as he circles the house. Ma keeps yelling: “get inside!”

That night as we sleep, the aftershocks keep hitting, and I crawl into Twin Bro’s bed. We cling to each other as the rumblings continue, for that entire sleepless night.

It’s our last year of Primary school; we’re twelve years old. The 9 am bell is still 45 minutes away, and we’re out on the tennis courts, playing against each other. Within ten minutes it’s turned to doubles, us against our friends, and right up to that opening bell we’re still undefeated. During morning tea we sweep through 15 minutes of tennis, still victors on the court. Come lunchtime we blast through two teachers, intent on ending our reign. A body blow with a tennis ball retires one, the other claims a bad back and shuffles back to the teachers staff room. The class below us is playing on the next court; their top player is sent over. We dispatch him back quickly, bruised ego to go with his bruised body – we never let a gentle return lob go unpunished. By the time the bell goes at the end of lunch, we’re playing against each other again, the court to ourselves.

It’s the following year, we’ve moved towns and moved school. It’s the first class on our first day, and the teacher is angry. The class sense he’s cracking, they become louder, disobedient, disrespectful. The teacher tells them as much, and then, unbelievably, slams his books down on the floor and storms over to a nearby window. He opens it, crawls through, and disappears out of the classroom. This was not like school back home. I look at Twin Bro and we both look out the open window; it sure looked inviting that day.

We’re 18 years old now, on the first day we’re legally allowed to drink in a bar. We head down to the local pub, intent on a quiet beer and a game of pool. We order our beer and sip on it as we wait for a game. Two old timers are finishing up, and as one triumphantly pots the black, we insert our coin and begin to rack up. The two men, stunned for a moment, bluntly point out the blackboard. We slink back to the table after writing our names down on the board, embarrassed as the two laugh at our inexperience. They sense an opportunity, and when our turn comes up offer us a game of doubles, with a friendly wager to start: a jug of beer for the winners.

Perhaps at this point we could have told them, that from the age of seven, we’d had a pool table in the lounge room. We’d played daily, mammoth multi-set games, for the best part of the past eleven years. We didn’t though; we just smiled, shook hands and asked who broke. They told us the challenger always breaks, so we broke, for the first and last time that evening.

As their losses kept piling up, like the empty jugs of beer on our table, their manner went from rude to ungracious to downright hostility towards our winning form. The beer was not dulling our effectiveness, instead unleashing more daring and ambitious shots from us, each one corralling the other to do better. In a desperate act, the men switched tact, betting top shelf liquor on each game rather than beer. This now necessitated one eye being closed as the balls multiplied on the table, and I took it to a new level by simply closing them when shooting for the black. And sinking it. Twin Bro evolved it slightly by looking over at the two men as he sunk the black. We never missed. Or lost. All night …

… Until they took umbrage with our antics (mainly mine my brother informed me years later) and challenged us to a different game, involving us, the alley out the back, and their fists. The bartender thought it best for us to take our leave.

So we swayed down the footpath towards home, and on the side of the road spotted the chassis of a lawnmower in the back of a parked ute. Taking ownership of the mower, I jumped on the front and Twin Bro raced me down the smooth asphalt, my frantic yells of ‘faster! Faster!’ echoing through the suburban streets. They were abruptly silenced as quickly as Twin Bro abruptly stopped – in front of a bark covered garden. Physics took over and I was flung into a bush, bloodied knees and elbows all askew. Remorse swept over my brother, and after checking for vital signs helped me back onto the mower. He drove me all the way back home, screaming the siren call of an ambulance as he ran.

Ma woke us the next morning, our heads throbbing, dried blood on my sheets, and quietly inquired about the lawn mower sans engine parked neatly in the driveway.

We’re thirty years old and I’ve traveled six hours across state. It’s late in the evening and we’re out on the porch. We sip on a beer and talk about the past. Mostly we can’t speak, the tears are flowing down our cheeks, our stomachs are buckling, we can barely breath, we’re laughing so much. We talk about the future and our dreams together; we plan our battles and talk up our chances. It gets late, we’re both tired; it’s time to go to bed. I get up and hug my twin brother, say I love him. He hugs me back, says he loves me too.

Hey Mr Peko-Train, this one’s for you.

(My) Teriyaki Chicken

          

We peeled potatoes side by side together, when we were young; cooked a cup of hot chocolate in the microwave for ten minutes too. We’ve barbecued together, cooked a roast together, had a forgettable Thai meal with his girlfriend once. Cooking has always been a constant for us, even from a young age: when asked what he wanted to do when he grew up, my four year old twin brother replied “feed the skinny people in Africa” … (Big Bro wanted to be a lawyer – even then I guess he liked the idea of arguing with people …)

So when I was writing this post I tried thinking of a recipe my brother would like. Stumped, I reached out and sent a text: “what’s your favourite meal to eat bro?” “Enchiladas” he sent back.

Right … well as much as enchiladas have chicken in them, so does my Teriyaki Chicken, so this is the closest your going to get bro. Hope you enjoy it.

Ingredients:

  • Tamari or Low Salt Soy Sauce
  • Sesame Oil
  • Shao Shing (Chinese cooking wine)
  • Rice Wine Vinegar
  • Mirin Seasoning
  • Palm Sugar (I use the ‘pouring’ kind, easier to measure out)
  • Tamarind Pulp
  • Fresh Chilli or Chilli Paste (optional …)
  • Fresh Lime
  • Soba Noodles (not the drunk kind … drum fill please …)
  • Ginger
  • Garlic
  • Fresh Coriander
  • Capsicum
  • Brown Onion
  • Celery
  • Carrot
  • Button Mushrooms
  • Baby Bok Choy
  • Chicken Breast (or thighs, de-boned and diced. I use two breasts for this recipe)

First … The Marinade:

This needs at least an hour to marinate (which is the most my patience has allowed) but would definitely benefit if left for longer.

(a small aside … I’ve made this recipe at least half a dozen times over the past month, and each and every time I’ve made an initial effort to record the quantities used … and then kinda forget half-way through. I’m a little slack in this regard, I’ll admit. So I’m guessing it would probably be best to be a little prudent, and use these quantities as a rough guideline; in my mind they are fairly approximate, and I’ve always believed that when it comes to marinades, more is definitely better. Hope that helps …)

First, grate a 1 by 3 cm cube of ginger, followed by around four to five cloves of garlic. Place this in a mixing bowl with the finely diced root of the coriander leaves (make sure you wash them thoroughly). Next, add around two cups of soy sauce, and around two teaspoons each of the rice wine vinegar, shao shing, mirin seasoning and sesame oil, a good squeeze of lime juice, with a tablespoon of the tamarind paste and double that for the palm sugar (which is why I use the pouring kind, it’s easier to measure). Either play Russian Roulette with a whole chilli, seeds in or seeds out, or use a teaspoon of chilli paste to add to the mix.

Mix this together well, and then submerge the chicken breasts, scoring each side of first around half a centimetre deep. Cover then refrigerate for at least an hour.

That is seriously the hardest part of this entire recipe.

Next … The Vegetables:

Take the capsicum, carrot, brown onion, celery, mushrooms and baby bok choy, and slice them up ready to be quickly stir-fried, making sure you have rinsed them all thoroughly first. I like to julienne all the vegetables apart from the mushrooms and bok choy: mushrooms aren’t all that easy to julienne, I just roughly chop these, and the bok choy (after rinsing!) I simply sliced length-wise. Place these aside.

Finally … Pulling it all together:

Take a large pot with a lid, or pan with a lid, place the chicken and marinade in (scrape the sides of the bowl …) cover with said lid, then leave to simmer for ten minutes or so (your chicken, your cooking time). After ten minutes, turn the breasts over, leave the lid off, and cook for a further five to ten minutes. Take off the heat, replace the lid, and leave to rest for at least ten minutes.

While the chicken is cooking, boil some water on the stove (in a pot, mind you, in a pot …) and cook the soba noodles for around four to five minutes. Rinse these thoroughly with cold water, then douse rather liberally with sesame oil, mix it in well, then set aside.

As the chicken is resting, fire up a pan to maximum heat (and in our household, open the windows and place a broom below the fire alarm, ready to bash it quiet when it inevitably goes off) and quickly stir-fry the all vegetables, except the bok choy. As it cooks, add a dash of the mirin seasoning, soy sauce and rice wine vinegar. As the bok choy takes about half the time, if that, to cook than the rest of the vegetables, stir-fry this last, after removing the other vegetables.

It’s all plain sailing from here … Place the noodles in the bottom of a bowl, add some vegetables (there should be some juices at the bottom too, add these!) then the thinly sliced marinated chicken, and pour over oodles of the chicken marinade. Finish up with some roughly chopped coriander leaves and a few drops of sesame oil.

So again, not quite enchiladas, but fairly close. Kinda. Hope you enjoy it.

Michael Cameron