by Looping on Thu Feb 04, 2010 6:23 am having had a very comfortable PID-ed double boiler machine in the past, yet I wouldn't want a PID on my commercial lever machine.
Why? From my point of view a 100% accurate boiler water temperature is not that important as it isn't responsible alone - it is just the starting point of the extraction process.
The extraction temperature varies throughout the shot - at first, the boiler water is still much too high, then the temperature drops during the preinfusion of, in my case, about 18 seconds, while the grounds and the metal absorb heat from the water.
Then there is the surrounding temperature in the kitchen (winter, summer...).
Of course, the grind, the amount of coffee meal, the shape/size of the basket, the tamp (soaking speed), all influence the heat absorption during the extraction.
Then there is the decreasing brewing pressure, after a full start, also influencing the flavour of the shot.
The temperature of the water in the boiler to me is only one parameter of many influences and thus I wouldn't compare the effect of using PID-ed boiler water has in a double boiler machine with the situation in a commercial (i.e. big boiler/massive group, thick tubes..) lever machine.
I've tested so many pstat settings throughout the last months, that my husband drilled a hole into the cup tray to make the pstat easily accessible and now there's a screwdriver sticking permanently in the pstat screw, so I can adjust it anytime
Of course, I still don't have a temperature display. But having measured the brewing water temperature at different pstat settings, I can roughly estimate the boiler water temperature from the boiler pressure indicated on the pressure gauge.
When changing the boiler pressure/water temperature often, I've learned that the boiler water temperature isn't all.
When I lowered the pstat setting as much as possible - and steaming milk over a longer time period had already become difficult - I could measure a low brewing temperature (with a K thermocouple, under the basket, in which lay a one time used coffee puck) but still a shot can taste burnt (not totally, but a little ashy or even having a burnt undertone), depending on the roasted beans used.
Apparently, the boiling water temperature in the beginning of the preinfusion, when the water streams into the chamber, can be too hot for a coffee blend.
Surprisingly, I currently use a blend to be brewed quite cool and despite a higher pstat setting (to be able to better steam milk) it doesn't have a burnt touch in the overall taste (I usually make a double ristretto out of 14,5g of coffee meal in a 14g double basket).
The pstat reacts quickly and is already very accurate. Depending on the sensitivity set, it could take some time until a PID has finally approached the desired boiler water temperature. Now I'm often pulling one shot after another. Then again, the group heating up furthermore influences the brewing temperature of the extraction...
And I don't change the setting often, anymore - it's now set as low as possible to be still able to steam milk well enough.
To sum it up - I don't miss a PID and I don't see a genuine advantage.
It was very useful in my former double boiler machine as it influenced the extraction temperature clearly, controlling a single boiler with cooler, non steaming water (as there was a second steam boiler operating - via pstat, by the way - at a much higher temperature), bringing it to the ideal brewing temperature so no cooling flush is needed as in HX machines.
On the other hand, a commercial lever is a single boiler machine operating with constantly boiling, steaming water in the kettle.
Apart from warping the striking simplicity of an almost non-electronic machine a bit - in my opinion controlling the boiler water via PID is only responsible to some extent for a good shot. Still the used blend must correspond to the machine.
I've retried many blends I knew from my former non-lever machines - and I think trying is inevitable - the lever shot is so different from a pump driven machine, it's like a concentrate, emphasizing the body, acidity and all flavours (also the less pleasant ones).
And when I've found a blend (or single origin roast, needless to say) that goes with my pstat setting (which cannot be lowered anymore in favour of a sufficient steam capacity), I'm all happy.
Only in rare cases I've stumbled over a roast that could be brewed at an even higher temperature.
So I don't alter the pstat setting often anymore, the testing period being over. If I wanted to, I could simply turn the screwdriver handle sticking out of the machine behind the cups. No temp. display, of course. But do I really need to know the current boiling water temperature that is still much too high?
I learned that the commercial lever machine types vary quite a bit. I can only speak on behalf of my Rancilio.
And I'm just a simple user
Cheers
Tanja
