Is it me or is everyone else a little surprised at the lack of discussion of pressure profiling?

Most of the interesting discussion, if not just about all of it, has been over at home barista where various people are building pressure profiling units for their one group machines.  Still much of that discussion remains more about how to build it, than about desirable profiles.

Pressure profiling is undoubtedly going to become more readily available.  Though the capacities of the Slayer, the Strada and Cimbali’s new machine are all different, they are all chasing the ability to manipulate pump pressure to improve espresso.  A lot of this desire comes from the profile of espresso produced by lever machines, which have a very different pressure profile compared to a pump driven machine.

Perhaps I shouldn’t be surprised, given my own experiences with pressure profiling.  I was asked, a little while back, about why I hadn’t posted anything about it and I thought I would take this opportunity to explain:

John Ermacoff very kindly leant me a pressure profiler that he had built for a while.  I am not going to go into exactly how it worked, but we hooked it up to one of the groups in my 2 group Synesso.  This meant that I could only use one group at a time because then I had a Cyncra, not a Hydra, so the changes in pressure would influence both groups if they were open.

The machine allowed for almost any profile, and included a manual and automatic mode.  I played with the manual mode for a while, but prefered the automatic mode because it was repeatable and allowed me to make specific adjustments.

The entire time I used it I felt lost.  Juggling dose, grind size, flow rate, volume of espresso and time is enough.  Suddenly introducing pressure variations meant that it was a lot harder to isolate the problem.  If the shot was underextracted then keeping the profile but changing one variable often resulted in chasing my own tale and very quickly burning out my palate.

Changing the pressure even slightly undoubtedly changed the cup.  The impact was always obvious, but rarely did I ever feel as if I had genuinely improved the cup.  By giving me so much control I ended up lost in a sea of variables from which I never really found my way out.

I confess that I didn’t approach this as clinically as I should have.  I didn’t record enough data and often ended up defaulting back to a very simple profile – which seems to be quite a popular one online:

• - A relatively lower pressure preinfusion period, lasting long enough to soak the cake (5-8s depending on dose).
• - A smooth, relatively quick rise to 9 bars over 2-3s.
• - A period of 9 bars lasting 7-10s
• - A declining pressure in the remaining section, from 9 bars down to 8 or perhaps lower.

This is by no means what I would claim to be the perfect profile.  It is one, however, that I could rationalise in my head.  The period of preinfusion at the start would increase the likelihood of an even extraction.  The period of declining pressure in the final third meant that we were extracting the nearly-spent coffee less aggressively, yet still adding volume to the shot – aiding balance, and reducing negative flavours.  Of course you could easily tear this theory to pieces – I just couldn’t find a better way to explain it.¹

One thing that surprised me was how a lever machine acts, as I had initially thought this profile would be quite close to it.  I was quite wrong – though my experiences comes from the use of a Victoria Arduino Adonis and a Scace 2.

In terms of pressure the lever allowed line pressure through when pulled down, as the machine has a heat exchanger for brew water.  Upon releasing the lever the pressure shot up to around 12 bars before almost immediately starting to drop down towards 0 in a fairly linear fashion.  I only found this out after I had returned the profiler, and I wish I could have tried it on the Synesso.  That way I could have dose two identical baskets had a better idea of the influence of temperature on our love affair with lever espresso.  The Scace 2 showed that initially the brew water was very stable – in the first 12-15 second after pulling the lever the temperature barely moved – maybe 0.2/0.3°C.  Then the water gradually began to decrease in temperature, losing 4 or 5°C by the end of the shot.  This makes sense.  When the lever is pulled water fills the chamber above the coffee.  Only once it starts to pass through the coffee, and lose thermal mass, dose it really start to cool off.²

This profile is a very long way away from what most pressure profiling machines out there are doing – or at least what people have said they are doing.  Then again, as I said at the start, I can’t find many people talking much about it.  I guess I had hoped to see more on places like coffeed, coffeegeek, twitter or on various blogs.  Personally I’d be as interested in finding out what isn’t working for people, as much as what is.  When I asked the Cimbali engineer which profiles he liked best, he was a little evasive – in fact very few people are willing to really get behind any one profile.  I know these may change coffee to coffee, but with enough data out there I hope we’ll eventually be able to make a pretty good educated guess, the way we can with things like temperature and dose, based on the density of a particular coffee/blend.

I do have great hopes for pressure profiling, but at the same time realistic ones.  I don’t expect pressure profiling to discover sweetness, or flavours that have previously remained undiscovered in coffees.  I hope they can improve the clarity and presentation of them and help reduce detracting tastes and flavours.  It won’t make average greens taste great, or bad roasts acceptable.

Right now it seems that engineering is, for once, way ahead of the barista.  The pressure profiling machines coming can do almost anything we want – we just need to work out what that is…

I will close this post by saying thank you again to John Ermacoff – I learned a great deal through his incredibly generosity, and can’t wait to see what he comes up with next.

1. If anyone has any info on the effect of pressure at that stage in the shot – on caffeine extraction, oil emulsion etc etc then I would love to see it!
2. Again, correct me if I am wrong here

My predicitons were:

1. Coffee Packaging takes a step forward

Nothing here to report.  I don’t know if anyone has done anything interesting in 2009 with roasted coffee packaging but I certainly haven’t seen it, and I don’t think it has had an impact.  A poor prediction.

2. Improved Green Coffee Packaging

This is a tricky one.  I am sure that this year people have received record quantities of vac-packed, or grainpro packed coffee.  I know that a substantial amount of coffee that we’ve bought this year has come this way.  I also know that it leaves me conflicted over the amount of waste this packaging generates.  An OK, passable, but not great effort at prediction.

3.  Someone invents a grinder worth getting excited about.

Nope. Nothing here.  I know why, from an R&D cost Vs sales perspective, this hasn’t happened.  For some reason I guess I thought it just would.  A complete failure of a prediction.

4.  Decent Coffee Press in the UK.

I am going to claim this one.  You could argue that the quality of writing hasn’t been where it could be but I think this year we’ve seen unprecedented levels of coverage for speciality coffee – mostly in response to Gwilym’s win – but also covering the blossoming of London’s coffee culture.  I hope it continues.  A pretty successful prediction.

5.  Producing countries in the WBC Top 6.

Another utterly failed prediction.  Raul was just outside the top 6, and I think there was some surprise at who made the top 6 and who didn’t.  Nonetheless I can’t even vaguely claim this one as successful.

So…  Barely 1.5 out of 5 I reckon.  Not good work.  I shall have to try harder for my prediction for 2010, or just give up entirely!  I hope next time I don’t confuse speculation and prediction with wishful thinking!

The one interesting thing, in terms of me trying to salvage my credibility, are the two main predictions that I got wrong in 2008 – the rise of pressure profiling and increase in green coffee pricing – have somewhat come true in 2009.

There can be no argument on the pressure profiling front.  From the Slayer to Strada, but also to Cimbali’s rather impressive pressure profiling machine – the technology is now here and seems to have perhaps captured the interest of manufacturers more than baristas but I think it will continue to be incorporated into new machines.

As for green coffee – it may not yet have reached the peak of March 3rd but after a steep drop it is definitely back on the rise:

(couresy of Wolfram Alpha – the rather splendid search engine for this sort of thing.)

I’ll post my predictions for 2010 around New Year.

These last few days have been a pleasant, but steep learning curve.  I know I’ve muttered about pressure profiling from time to time, but I hadn’t really played with a lever machine properly until Gwilym’s WBC prize arrived. ¹
I am not quite at the popeye arms stage yet, but I could see how you could incorporate a machine like this into a serious workout routine.  I have had some delicious shots, but I have had to abandon the traditional time frames I have used for espressos I know well.

Lots of little things make an impact.  The size of basket has a very strange impact – keep the dose the same, but have a bigger basket means that more water fills the chamber above the coffee meaning you will pull a longer shot.  Changing basket but keeping the dose the same has enough of a weird impact using my Cyncra, but this one single variable has a terrifying domino effect on the shot!

Gwilym came by today, he’s on his way to Italy to visit La Marzocco and wanted to pick up some coffee to play with.  We thought it would be fun to pull some shots of the same batch on the Athena that he’ll play with out there.  The impact of even tiny adjustments to pre-infusion time made an astonishing difference to the cup.

As you can see from the photo above I dug out my Gaggia naked portafilter, as I was curious to see what effect the lack of dispersion screw would have.  (This is the first machine I’ve used without one).  Turns out it is nothing noticeable, but then I am not sure how much detail can really, really be discerned from a naked portafilter.  They do still look pretty though.

Shot times appear to have gone out of the window.  Or at least the window has moved quite substantially.  People who go to Naples often seem to come back remarking on the 45 second shot time.  I haven’t had much under 35s that I’ve really liked, though I haven’t played much yet with barely any infusion so that may change things. ²

Now I’ve never been one to worship at the altar of crema, I don’t want more of the stuff, I don’t read too much into its texture or its colour.  However from an aesthetic point of view the shots from the Athena do look remarkable pretty.  Darker espresso roasts than ours mottle/tiger stripe in a wondrous manner (had some very tasty shots of Espresso Rustico from Counter Culture which I wished I had photographed because I think they’d be an interesting reference point for barista competition judging).

I can’t quite put my finger on exactly how the shots change.  I also admit that I’ve had more experience than most with pressure profiling, and the impact of soaks and ramps.  I do know that you can get some very interesting textural and taste based results (I am separating taste from flavour here), but I also know what a knife edge it can be.  I’d love to pull a few hundreds shots on one of these and see how you build a workflow around them, would it lull you into a pleasant and soothing rhythm or taunt you with its crawling pace.  Plus if you pull a choker then there isn’t much you can do except be patient. ³

I consider myself very lucky that Gwilym has kindly let us play with it.  If you are coming to roastery any time soon then I’ll probably try and force a shot or two onto you and talk in an overexcited way.  I am aware this post comes off the back of a post about how silly espresso is, and how we should all love brewed coffee, but from a personal point of view it is rare that I get the opportunity to go through a learning experience like this one.

I’ll try and post more about it all as I learn a bit more and have something solid and interesting to say.  If you have experience with lever machines then I’d love to know your thoughts.  If I have one gripe with the machine (and this is exceptionally churlish, considering I am borrowing a friend’s prize) it is that the cup tray is really quite tiny.  Petty?  Me?  No….

1. Yes, we kindly offered to ‘look after’ it for him for now…
2. For the record I would start the time the moment the lever is sufficiently pulled down that you can hear the water entering the brew chamber.  Other than that it is noticeable how eerily quiet the whole process is.
3. I have been told a couple of methods to interupt the brew, but frankly they either scare me or increase the likelihood of me making a mess of my clothes and I just can’t condone those things.

1 – The spread of the Clover.

I could be really brave and predict that Starbucks will start using
them, but I think the guys at Clover would curse me for jinxing them!

I think I did pretty well here – though no one predicted Starbucks buying them outright.  You could argue that Starbucks haven’t really spread them around, but as I am not in the States I don’t know how often they are cropping up.

2 – World Barista Championships

I am not going to be as bold/stupid as to try and pick a winner but I
think the shift away from a Scandinavian-heavy final will continue.

2 of the 6 finalists were Scandinavian, but neither placed in the top 3.  I feel pretty safe claiming this one!  Congrats again to Stephen!

3 – Coffee prices continue to rise

I am not sure I am going to be able to claim this one.  Whilst things did look good (briefly) for this prediction earlier in the year prices seemed to have slumped at the end of it.  (Don’t worry – I am not going to go on about the media exaggerated financial issues).

4 – Pressure Profiling in Espresso

I am not sure on this one.  Synesso released the Hydra – the first machine with a pump per group as far as I know, LM released their new paddle group, John “The Awesome” Ermacoff kindly built me a pressure profiler that makes my head hurt but makes me happy, and the new Slayer machine also is big on pressure profiling.  All the above says yay, but I don’t feel we’ve come much further on understanding it all.

5 – The continued rise of the Microlot

Again I feel the need to plead my case here.  Certainly this was the year of the Ethiopian microlot – the numbered lots from Aricha and Beloya getting everyone very excited for good reason.  This was the year that Esmeralda divided their crop into micro microlots for the auction.  This was also a year that my understanding of microlots got a little more nuanced, and I felt less sure that they were all I had wanted them to be 12 months ago.  From this point on I leave it up to you dear reader – how well did I predict the year?

(You can add your own half point answers if you feel the need)

Would love to hear your comments on this.  I think I’d like to claim 4 out of 5, but that is up for debate!  Look out for my next set of hilarious predictions come January 1st!