Catch up

I have been pretty busy, in the most positive of ways. There is so much potential for collaboration, exploration and rewarding experiences in coffee.

It’s been a while since I wrote here, so I thought I would do a little summary of the projects I am involved in, a bit about each and the hope of expanding on each in the near future. I have always loved the medium of a blog to get ideas and thoughts down on paper.


Water for Coffee

Several weeks ago, myself and Christopher H Hendon released our self-published book on the topic of water for coffee brewing. This was the culmination of research over the past couple of years. The book has sold really well and the coffee community definitely appear to be enthralled and interested in this amazing topic.

One of the most positive aspects of being able to create a book like this and get it out around the world, is how the dialogue and discussion suddenly widens. There will always be more we can learn with a topic like this, as it is with much in coffee.

An immediate and fundamental point to consider, which has been gained from the input of readers is that of standard water measurement. We are interested in the individual aspects of the water’s mineral composition and how the role they play in the extraction and flavour organising process. However, it has become abundantly clear that the standard unit with which to communicate hardness in water is Calcium Carbonate (CaC03). This basically means that if a specification is written with CaC03 as its reference you then have to figure out a conversion to get your actual amount of calcium for instance.

We have explored this concept in a written corrigendum (an error to be corrected, esp. an error in print). This is available here and is supposed to accompany the original volume. Research into this topic continues, by ourselves and by others. This is an evolving project and we intend to release a volume two next year with additional content.

The particular point to take from this is that it is very important to know that these two ways of expressing mineral content exist. This is specifically important when interpreting a specification and when understanding the result from a measurement device that may measure in either expression.

For example take two interpretations of the SCAA water metric.  The larger box interprets the numbers presented by the SCAA as straight ion whereas the other box denotes the same numbers when considered as CaC03, therefore resulting in a lower actual ion reading.

scaa water

More research

Coffee is full of hidden details that can be better understood and explored though scientific practice. A personal fascination of mine is coffee grinding. I have written about this at length before, here and here.

There is doubtless much research to be done with grinding, as it seems that when one question develops an answer, then several more questions arise, with the potential of several more tests to be done. Like the Water book, research here has greatly benefited from collaboration.

I feel there are several aspects to grinding coffee. There is the distribution of particle size, from the very small to the not so small and what this means for extraction. It’s very hard to test a single variable however, as by grinding coffee differently (by changing the grind) we may be effecting heat transfer during extraction or flow rate during espresso brewing. There is then the issue of dosing and distribution.

One of the topics that was explored in a previous blog here and has been expanded on by others is the impact that the temperature of the bean has on the particle distribution of the ground coffee when the burr setting remains constant. This presents a good test as the variables are controllable and the answer we are looking for can be relatively easily measured. Well, you need a laser particle analyser, which Chris managed to wrangle for a day’s use in our shop.

Myself, Chris, Matt Perger, Cristian Klatt from Mahlkonig and others, are currently finalising a paper to be submitted for review and hopeful publication on the effects of heating on particle distribution. The paper will include some other interesting and surprising findings.

One of the revelatory perspectives I have found and like to present, is the 3 various ways that a particle analyser can display the same information. Below is an image of one set of data interpreted to represent volume percentage, surface area contribution and number count.

partivle dist

I find this a tremendous display of how the question asked can completely change the answer based on the same topic, in this case data on ground coffee. Volume % denotes how much of the overall volume of the ground coffee is taken up by that particular size of ground. A boulder or larger particle will take up a lot of volume and present itself as prominent on a graph that interprets only volume. Smaller particles will take up a fraction of the space and will appear less important in this interpretation. When the data is adjusted for contribution to surface area, everything changes and the smaller pieces become far more influential and start to dominate the interpretation. They may take up less space but they contribute a lot to surface area. Lastly we have number count. This changes everything again. In this espresso grind the particles under 100 microns contribute to roughly 20% (this number is derived only from this data and one grinder model) of the volume but this twenty percent is made up of a hell of a lot of those small pieces. When we change the data interpretation for number count the data suggests there are almost no pieces over hundred microns. Fascinating stuff!


Colonna – Sourcing and roasting

We have started a roastery, well just about. We have a premises, some rather special green coffee and various equipment making its way through customs. We are tremendously excited by this project. I could explain the concepts behind the project here, but an interview by Sam Maccuaig for Sprudge does a great job. You can find it here.

A lot more on this venture coming soon.



Sanremo are an interesting company, one undergoing a massive change of direction. This started with a collaboration with John Gordon a few years back and resulted in the Opera espresso Machine. This machine will be presented in its final updated V2 form at Host in Milan in a few weeks. It will be accompanied by other new projects that Sanremo have been exploring. This year I was asked to become part of an international development team. Together we are working on new equipment aimed at the cutting edge of what’s possible.

I joined this project not only because it provides an opportunity to get behind the scenes, to learn more about, and be involved in the technology that we utilise to make delicious coffee, but also because the company proved to me to have a flexibility to become inspired by a concept or a goal and to approach it creatively and to make it happen. The international group I’m working with is of an amazing quality and it’s very exciting to see where we can go together.

If you are at Host I hope to see you there and to serve you some Colonna coffee; that is if a certain roaster makes it through customs in time.


WBC development board

I guess you could say I am currently retired from competition. Never say never, but I won’t be competing for at least 3 years. I took the opportunity to become involved in the WBC development committee which is currently exploring how we can evolve and develop the World Barista Championship. Being so heavily invested and involved as a competitor, it is fascinating and rewarding for me to get behind the scenes. The coffee competitions have played a huge role in the speciality coffee community and I am sure they will continue to do so.

It’s intriguing to assess something that is already very successful and to look at where it can go. It is easy to criticise something like the WBC, I myself have been a critic of certain aspects during my competitive career. I do think the competition can improve, but it’s also important to be aware of what works, of what makes it special and to maintain that whilst addressing the elements that can improve.

Unfortunately (but also naturally and sensibly) I can’t divulge the details of this process. You’ll just have to wait and see what changes in the coming years.


National Coordinator SCAEUK

Speaking of competitions, I have taken on the role of National Coordinator of the UK chapter of the SCAE.

Much like the WBC board, getting involved in the running of the UK chapter really appealed to me. I am working with a great board over the next couple of years. Our goal is simple really. To take the potential and support for these competitions and to maximise and explore it, creating as much value as possible for all of those involved.

There is a lot of support for the chapter and that has a huge impact on what we are able to do. In summary we are looking to expand the nature of each event, hosting the competitions and the heats at venues that reflect the speciality coffee community. We are looking to further the success of the UK Barista championships but to also make the most of the increasing popularity and potential of the other competitions.

For updates and info keep an eye on the chapter’s website here.

That’s all for now.

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What’s Your Real Dose?

Chatting away with Jonathan at Repack espresso(conveniently located near my house) this morning was the beginning of this blog. I thought the conversation provided a neat narrative for considering the impact evenness and extraction can have on how we percieve brew ratios.

We chatted about the conceptual differences between an EK coffee burr espresso recipe and other grinders, in this case, his Anfim grinders.

What is your real dose and for that matter real extraction?

Let’s say that we both start with a 16g dose and dial a coffee in to achieve a desired extraction and strength.. Jonathan dials in a single origin coffee in his store (a roaster and coffee we also use in our store). I however dial this coffee in at our store and use an EK with coffee burrs. My recipe that achieves a flavour of both strength and extraction that I am happy with is predictably a longer shot – 16g in to 39 out. This tends to be common practice for an EK. Most of our shots are around this mark. Jonathan’s is predictably shorter – 16g in to 34g out.

There’s a touch of dryness on Jonathan’s shot but its really good. After chatting about our recipes he tries a longer shot but as is often reported it was thin and over extracted tasting.

It’s easy to think we are using the same dose in and exploring the same yields out. But we are not.

The difference is all about evenness. Conceptually its easy to recognise that a more even grind means we allow the water to access more of the coffee at once. This then means that the we can hit a higher extraction without the over extraction taints we have correlated with certain refractometer numbers. For example EK shots often taste under extracted at 20 percent, whereas as similar under extracted taste is achieved at a 17 percent reading on another grinder. This isn’t exclusive to grinders though. The physics of even extraction that can be improved with lower flow rates/pressure (as explored in the previous two posts) present a similar phenomenon. Extractions that peak at a higher number when the brew is tasting its best compared to before.

In both cases we are extracting more evenly, and nowhere is evenness more impactful than when brewing espresso.

As these change, so does the use of reference points, such as brew ratio and extraction.

So, back to the title, In both cases – lower extractions that taste balanced and higher extractions that taste balanced- are the doses of coffee we are starting with actually the same? Well, as a dry weight on the scales, Yes. But, as far as the water is concerned, No.

If the grind is less even or we are extracting from less of it from some reason, then we are not actually using 16 grams, maybe we are only using 14g. I don’t know for sure, but for arguments sake, let’s assume it’s 14. From a grinding point of view , if we get a load of boulders, as we may from a Robur, then that “coffee material” is not fully accessible to the water. Part of the 16 grams is tied up in the bolder, essentially taking down the dose you are actually brewing with. The same goes for the physics of brewing, lets say the water passes through the coffee less evenly, either because of distribution, flow rate or evenness of grind. The water will be using less or more of the dose, effectively completely altering the brew ratio which we so often discuss.

This then impacts hugely on the refractometer reading, especially when converted to represent extraction.

When we type in the TDS% reading to the mojo app, we also type in our starting dose and shot weight. The calculation that takes place considers that we were extracting from the whole dose, in this case 16 grams. What if using a less even grind actually meant we only really used a dose of 14 grams? If we then type this as our starting dose into the mojo we would get a much higher extraction reading.

So in essence, are EK shots really that much of a weaker ratio than other espresso shots? For example the two recipes myself and Jonathan decided upon when using different equipment seem very different on paper, but in reality they may be much closer than they first appear.


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Pressure & Flow Restriction

It was terrific that the last post was so well received. It would seem that from others’ experiences and some more of my own that a lower pressure/flow has the potential to improve extractions irrespective of the grinder. The suggestion being that lighter roast coffees are harder to extract from evenly as a pressurised pour over (aka espresso) and that a lower flow rate helps with this.

The dialogue on the topic of pressure has mostly suffered and been stifled by the conceptual differentiation of flow rate and pressure. I was motivated by this misconception and wanted to explore the language and theory in this post.

We can start by stating that flow rate applies only to water and pressure refers to only the pump. In an espresso machine, the pressure determines the flow rate of water, but this pressure is not the hydrostatic pressure of water.  The pressure in an espresso machine refers specifically to pump pressure: whatever technology the pump is based on. Flow rate and pressure are not the same thing when dealing with gases, but all we care about when talking about coffee extraction is the rate at which water is pushed through the coffee bed.  Before we can explore the physics, we must go on the journey water takes through the machine.

When we make an espresso, water is forced towards the group using some sort of pump.  This force comes from applying pressure to the water.  But this does not mean that the water is pressurised.  Where did the word ‘pressure’ come from in terms of espresso machines?  Pressure is an important measureable for gases and most espresso machines force water through the pipes using some form of pump.  This is very different to applying ‘pressure’ to water.

Now that the water is moving, it progresses through the group, followed by exiting the shower screen.  It then comes into contact with a resistant barrier (the packed coffee dose).  Instead of permeating through the coffee, water is continually pumped into an open head space above the coffee. Once all of this space has been used up and there is nowhere else to go the water is forced through the coffee.

The coffee and the holes in the basket are effectively the exit point for the water. They’re simply resistors, so the flow rate is defined simply by the rate in which the coffee travels through these resistors.  We use liquid water to make coffee, which makes the discussion of pressure somewhat easier. Unlike something like air that will readily compress significantly under pressure, water is almost completely uncompressible. For example, at 4km beneath the ocean’s surface water only compresses by 1.8% by volume. Hydraulic cranes work by filling metal sleeves with water that will not compress even when lifting very heavy objects.  We know that water expands when temperatures deviate from 4 ºC, but, in terms of an espresso machine, the density of water is only a function of temperature, not pressure, and this means that we can measure the flow rate in L/min.  Any object in the way of the flow of this water will slow its rate.

It gets tricky here, because in an open system (where the water can leave by for instance flowing out of the basket) means we must consider displacement. The water entering the basket displaces the water already occupying the basket. Given that the basket (including coffee) is the resistor; the rate of displacement defines the “pressure” in the basket. Note that this effective pressure is simply measured by flow rate, and hence if the pump pressure decreases the flow rate does too.  Not because the water itself is less pressurised, but because the force pushing the water is less.  When we increase pump pressure we increase the flow rate of water exiting the shower screen and vice versa for a lower pump pressure.

There is another way to lower the flow rate coming out of the group head called a flow restrictor.  A flow restrictor is basically a little pipe that the water passes through during its path to meet the coffee. It effectively funnels water into a narrower pipe, and like traffic on a motorway getting pushed into one lane, the same volume of traffic will now take longer to pass the same distance effectively slowing the traffic rate.

If we consider a machine that has a pump achieving 9 bar pressure pumping water through the group. We then install a narrower flow restrictor in the path. This slows the flow of water down at the point of the flow restrictor, which directly decreases the flow immediately after the flow restrictor.  Our  pump pressure remains high,  but the rate at which the coffee brews goes down.  We have effectively lowered the flow rate using a flow restrictor rather than just lowering the pump. There are mechanical issues to consider but in essence the flow restriction and pump pressure impact flow rate the same way through different modes.

It’s much easier to just adjust the pump rather than exchange a flow restrictor.

To help illustrate this problem, below is an image that show that as the flow restrictor becomes narrower, there is a greater difference between incident flow rate (i.e. incoming pump pressure) and exit flow rate (i.e. the flow of water after all resistors have acted on the water).  Furthermore, you can achieve exactly the same effective flow rate with any flow restrictor, Simply by adjusting the pump pressure to compensate for the flow restriction.

This first image displays how different in going flow rates create different out going flow rates with different flow restrictors


This second image displays how flow rate going in can be altered to achieve the same outgoing flow rate when the flow restrictors are different.


It would appear that discussing pressure and flow restrictors over complicates the discussion. In terms of sharing brewing parameters it makes more sense to describe the amount of water that exits the group in a given time with no resistance. This way we implicitly understand the relationship between pump and flow restriction on a given machine.  It also removes the obvious variable of grind size, which directly determines how strong a resistor the coffee bed is.

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15g baskets

We have moved over to using 15 gram baskets to brew all of our espresso in store.

I have explored in other posts how our recipes and practices have changed over time. How the value of ristretto style shots became questioned , especially if the goal is the fullest character in the cup. Then how the very definition of espresso has become more malleable and ranging. Longer shots, lungos and the like have gone from being seen as travesties to tentatively and logically considered, to then being fully recognised as positive ways to brew coffee.

Of course, brewing is never in isolation. It is linked to the coffee, grinders, water and roasting. Light roasting can work very well but it is also in danger of not fully developing the coffees character, which is reason in the first place to move away from darker roasting. But baked coffees start to pop up and under developed coffees become very common, both in the flavour form of light grassy sourness or as a brothy vegetal toastiness(where the coffees isn’t developed  but has been roaster darker to compensate).

It can sound obvious, but many roasters I speak too are looking to now roast the coffee as fully as possible before they get the taints associated with pushing it too far – ashy, toasty, heavy. This is a seemingly small but significant conceptual move away from roasting it as light as possible before it is too light. After all, its the roasting process that harnesses the coffees potential and produces flavourful by products. Roasting is a tricky subject and I am excited to explore it in depth ourselves shortly. It’s also great to have more openness about roasting theories within the community, much like the world of brewing has seen, especially as it is all intrinsically linked.

A full even extraction is part of this process of understanding. It’s a complex feedback loop. Roast the coffee to be more soluble and you can achieve shorter shots with higher extractions and vice versa, in that less soluble coffee will need more water to achieve a higher extraction. Seriously underdeveloped roasts will struggle to reach high extractions at all, regardless of the amount of water. Solubility is an interesting indicator of roast and it’s a piece of terminology that is becoming more and more used. Roasting coffees to the same solubility is a concept that I have seen more of. It is also curious to consider how the same solubility could be achieved with different flavour development. But like Extraction numbers in brewing, it has the potential to improve the data and the conversation.

There’s a lot I want to taste in a coffee, I am looking for espresso to have intense complexity accompanied with sweetness whilst also being clean. I also want it to have the body and tactile qualities that set espresso apart (I’m a big fan of lungos, but see them a s different drinks).

In store we have moved to brewing all shots on the EK43. Our preferred recipes often ended between 35 and 45 percent brew ratios. The only downside is that the shots were getting long. Simply put, I didn’t like the way they sat in the espresso cup, they were also often too much. We have In our store always presented espresso as a one size beverage  as opposed to doubles & singles.

Over the years we had dropped down from 20g baskets to 18g baskets. We then thought, hell, why not go even lower?

So we got hold of some 15g vst baskets. The plan was to simply scale down. Keep the same types of ratios and extractions but just have less of the same drink in the cup, effectively reaching a desired portion size.

My initial concern was that it wouldn’t be this simple. The diameter of the dose remains the same, but the depth decreases. This presents questions for both flow and temperature.

Is a shallower bed less or more likely to extract evenly? Also, with a higher percentage of the dose now being immediately accessible to the water, as well as less overall temperature decreasing energy from the dry coffee, will the overall temperature of extraction remain higher?

Our biggest challenges with the drop in basket size have all been to do with restriction in the basket and the ability to get consistently high and even extractions. VST acknowledge the fact that as the basket depth decreases and we use less coffee, the amount of resistance the water faces, changes. The pressure in the basket effectively decreases as the amount of coffee decreases. VST aim to counter this by changing the frequency and size of the exit holes. The goal being to achieve the same resistance basket to basket. Ideally, the same grind should result in the same ratio to coffee to water in the same shot time.

For us it didn’t work. This may be to do with the grind distribution or the roasting styles. With the coffee burrs we just couldn’t get the shot slow enough, and the extractions high enough. We then moved to the Turkish burrs. This did allow us to achieve slow enough flow rates. The extractions went up but they weren’t consistent. The crema was erratic. Finer again didn’t help matters. We were hitting a celling on extraction and it would appear that by going so fine we were actually lowering the extraction, with the bed creating pockets of clumped fines that hindered the flow of the water, in essence having a coffee puck full of channels. This was something I had heard of before but had not encountered so obviously.

Next we took the dose up to 16-17g to increase resistance/pressure so that we could grind a bit coarser and hopefully achieve more even extractions. We collapsed heavily to keep head space, evenly distribute the bed and worked a nutating tamp in to the mix. Results improved. We also dropped the temperature from 95 to 93 to compensate for the potential increase of overall brewing temp and this also slowed the flow down again. This was all with the Turkish burrs. I still preferred the results I could achieve with the coffee burrs in bigger baskets.

The real success came by taking the pressure down to 6 bar. I was thrilled to have someone suggest this to me. On the San Remo Opera this gives us a flow rate of 190g of water in 30 seconds (straight out of the group with no handle inserted). If the pressure and flow are relative to restriction then it makes sense to lower pressure as restriction is lowered.  This has allowed for use of the coffee burrs again. The results in the cup are top notch.

The exploration of this basket size, was as you can see not without its problems, but the successes are multiple – espresso beverages of our desired serving volumes, with full, even and flavoursome extractions, that saves us coffee and money. Happy days.

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