by RayJohns on Tue Mar 22, 2011 9:31 pm
Just wanted to follow up a bit on this thread...
I have since gone back to using slightly shorter extraction times. The super long extraction times (at lower temp) did product some nice espresso, but something about it was just off a bit. I think it maybe extracted too much from the coffee. It was almost like the method extracted too much and the flavors were too bold.
I think part of it was also that some beans seemed to grind down and have more of a tendency to choke out the extraction than others. To combat this, I made the grind a little less fine and did not tamp as much. This allowed the water to go through the coffee a bit more readily. The extractions are still a little longer than the 25 second range, but the flow is better and I think there is also less likelihood of channeling. I would say the pressure on the lever is also about half as much.
Another thing I discovered is that a lot of the problem I was having was from having too much steam in the water that was reaching the group head. It seems the best espressos result from extractions where the water in the boiler has cooled down to where there is almost no pressure (sometimes, in fact, there is so little that I have to flip the machine on to the "II" settings for a few seconds in order to generate enough pressure to push the water up into the group head). In this cases, the flow is very thick and less foamy (less steaming hot water in the group head is the reason I think). This seems to produce the best espresso for most of the beans I'm using.
Along these same lines, I've been giving some though to installing a PID on the boiler. This would allow me to control the temp in the boiler using the PID, instead of heating the machine up, then turning it off and hoping I pull the shot at the right moment. However, in reading over all the "La Pavoni / PID" threads, it seems that the main issue is this: at the ideal brewing temp, there is not enough steam pressure in the boiler (to force the water up into the group head). This is similar to the issue I run into now actually. If I heat the machine up, then turn it off, then in some cases it cools down to where there is no longer enough pressure in the boiler.
My proposed solution to this is to attach a gauge to the machine, along with a small hand pump. My thinking is that the PID would control the boiler temp; when I'm ready to pull a shot, a few pumps from the hand pump would put enough pressure into the boiler and be enough to push the water up into the group head.
Anyway, the main point here was that going back to shorter extraction times does seem to work slightly better. The super long extraction times were interesting, but the flavor was almost too much. Also, when the water was too hot, it allowed too much contract time between the water and the coffee. If the water was lower temp, then it wasn't too big of an issue. Still, however, shorter extraction times seem to produce very nice crema and a more smooth / balanced flavor. A lot has to do with the beans also. It seems some beans just lend themselves to less clogging of the basket with finer grinds.
Ray