plunging the thermocouple to increase boiler temp / steam pressure

askthecoffeeguy

So we adjusted the thermocouple by a half rotation on my BFC on Wednesday, and it appears to have made a substantial difference to both the quality of our coffee and our ability to produce volume under pressure!

The main reason for the adjustment, followed by dropping water from the boiler and then allowing water levels to normalise, was to increase steam pressure in the boiler by creating a greater head of steam, so that we could improve milk production during busy periods, but as an unintended consequence we've also increased water temperature in the boiler - which had dropped off a bit anyway from continuous usage

But now I'm noting that the machine has a bit more 'pulling power' - in that it has a slightly increased ability to run  tighter shots with a bit more power, shaving a few seconds at most off each extraction - which  doesnt seem like much, but when you combine this with quicker turnaround times in the milk production, it means that we're able to get the coffees out faster when we need to most

I'm yet to measure the water temperature at the group head - but the main proof is in the cup with I would suggest remarkably improved definition of the flavour profiles of the coffees we're using - with some exceptions - and I would estimate that the boiler temperature has increased from 92 to 94 or 95C

The one exception is that the Colombian Huila SO coffee that we use tastes unpalatable IMHO after the modifications, whereas previously it was 'unique; and 'distinctive', now it is sour and overly acidic, which, through a process of trail and error my roaster and I have put this down as directly attributable to the increase in boiler temperature!

So it definitely doesn't work well for all coffees - but I've had no problems with the seven or eight other coffees that we use on a regular basis, which if anything seem to be significantly enhanced  IMHO but the alterations - an unexpected boon of temperature adjustment on a HX machine (BFC Synchro)

Have others played around with temperature and if so what have been the results?

Cheers,

ACg

mycuppa

A very interesting topic ACg and one that I personally have a tendency to spend way too many hours testing and thinking about. It is very easy to chase your tail with this one and sometimes I've not ended up any wiser. There was a move about 3-5 years ago towards higher temps. This was when the likes of LM, Expobar and other machines came onto the market with adjustable PID's - allowing the operator to very easily wind it up or down and then test the results in the cup. It was also when running SO's started gaining traction and it became more evident that some bean types preferred higher temps whilst others preferred lower. A few of the roasters around town started talking (and believing) that higher temps were generally much better for their "cafe" blends as it was addressing some basic (or even fundamentally major) sourness from the extraction. Whether this attempting to overcome a technique or roast issue is not clear. It certainly appeared that higher temps were the go and talk about 93 - 94 became the holy grail. Of course, some (or I should say most) of this testing was performed without the appropriate temp measurement equipment. And who's to say machine X running 93 is the same as machine Y running 93. When I do my testing in the roastery, I use a 2-group multi-boiler PID with the left group setup to 90 and the right group setup to 93 - just so I can get a reasonable assessment of a new SO or blend. This may not translate to all my cafe customers as some will have similar equipment, but others may not. The testing I do is just for my memory bank. One of my roaster colleagues uses a high proportion of Colombian in his blend (anywhere from 40 - 60 %) and his coffees certainly do prefer a cooler machine. The best coffees of his we have enjoyed have been from a really old Boema 1 group commercial that runs at something like 89 (estimate only). I have an old La Pavoni T2 Bar that runs pretty cool (I think) and to this day I still believe the coffees from this machine are some of the best I've tasted. The other one that sticks in my mind..........we supply quite a few large offices that have big Super-Autos. Most of these machines run pretty cool, yet the coffee I would normally suggest running at 93 in a cafe commercial espresso machine, tastes superb on the cooler Autos. So, there is both a case for cooler temps and a case for higher temps. Roasters with experience, who actually cup their batches on various types of equipment will get to learn what beans, blends and more importantly roasting techniques suit higher or lower temps. Sadly, there are some roasters out there who don't cup religiously, or are limited by what equipment they can test on, so may never get to fully understand the affects of temp on flavor. My personal thoughts........... Yes, to a certain extent temp plays a big part and I've seen some pig machines with seriously wrong temps pull awful coffees. Sometimes I think it's more a case of a machine may not be right and a slight tweak gets it running better. The bean and roast can also play a critical part and I like to think that it's a 50/50 situation split down the middle of how the roast was produced and then what temp it was extracted. Matching this is secret squirrel business. I see the biggest challenge is that you take roast batch A and then run it on machine X at different temps and notice differences (or what I like to refer to as preferences). Yet if you took roast batch B of the same bean/blend but prepared (roasted) differently and then performed the same experiment you may be surprised with the results being somewhat contradictory. Thus you can chase your tail.

beanflying

Interesting topic for me too.  After playing with a blend recently I noticed a slight sourness to it from my 1 group Lever which is currently being run in an open fronted garage (colder due to winter). Took the blend home and ran it on the Syphon (around 93C) and on the Pavoni running a little hotter than normal and lost the sourness. So I finished up giving the P/Stat a tweak to just under 1.1bar from just on 1. Result is the slight sourness has gone. Back on some of Jeff's Suuweet blend and it the shots weren't as good so back closer to the 1 bar again. Net result is don't be afraid to tweak carefully just a little either side of where your machine is currently set. There is some interesting reading here on what a 0.1 bar rise does to the boiler temp (only about a 1 degree C rise)  http://www.home-barista.com/hx-love.html so while some might think a 10% increase large the resulting temp change in the boiler is only small.

askthecoffeeguy

I've also often wondered about temperature profiling during extraction - conventional wisdom has it that a flat profile is better but I'm not sure that this has been adequately put to the test - although surely its only a matter of time before some savvy manufacture puts out a machine with these specifications and markets it as the latest new thing in espresso machine technology... p

beanflying

I have seen some temp profiles taken of lever shots not very flat at all, just tasty ;D