I may have had a breakthrough today.
I've been trying to understand a factor that I prize in great espresso - the sense of "clarity" of flavours. By this I mean that experience you sometimes get in a great shot where you can taste all the component beans and all the component flavours of all those beans - where there is this sense of "definition" of flavour in the cup. This is something I particularly value in truly complex espressos like the Hairbender or the Hines Espresso blend.
Ever since my first home machine review (of the Mia) I've been obsessing over this elusive characteristic. I discovered that I was not able to get any sense of clarity with the Mia or the Astoria. This is not to say that the espresso didn't taste good. But I was missing that weird definition.
I then came to the realization that I had rarely experienced this clarity in shots from commercial machines either. In fact, the only machines that seemed to be able to produce this were the temp-stabilized top commercial machines like the Synesso or a temp-stabilized Marzocco or Mistral. But... that being said... I also had noticed that there were examples of such machines where I was not able to get that clarity - so it couldn't just be temp stability. Hmmm...
I'm currently reviewing a home machine that seriously kicks ass (the Fiorenzato Briccoletta). Now, this machine has a couple of unique characteristics. First - it has a Procon rotary pump like the big boy commercial machines. And secondly - it is plumbed in. Now... as I'm reviewing it, I decided to run it off bottled water. But I didn't want to risk damage to the machine, and also didn't want to have to pay for tons of 5 gallon bottles of Crystal Geyser. So it's hooked up to a FloJet pump system (to mimic line pressure) and a Everpure Filtration canister.
I've been working really hard (with tons of advice and assistance from knowledgable folks who understand Heat Exchanger machines far better than I do) and have reached the point where I can be very accurate not only on brew temp but on temp profile. Thanks to some research by Dan Kehn, I've become able to "mimic" the temp profile of a Linea. But I still was not getting the clarity I'm looking for. Damn it!!
Today I went to reset the brew pressure on the machine as it's been running too high (10.25 BAR instead of 9.25 BAR). After doing so, I pulled a shot that was damn near perfect. Incredible clarity. Wow!! Hunh?
So I started to play around with the setup trying to understand it. In doing so, I came to an amazing discovery. If I had the pump running straight out of the water tank I could see "flutter" in the brew pressure while monitoring it. If I had the pump running off the FloJet but without the water filtration I could still see the flutter. In addition, shots pulled both of these ways lacked the desired clarity.
But when the FloJet and the water filtration unit were combined, the flutter went away and the clarity returned.
The light goes on...
I think, or believe, that the filtration unit is acting as a "dampener" of sorts. And I think, or believe (or perhaps hope) that this clarity is a result of control of the brew temp profile and a consistent brew pressure.
Man... if this is true it's a very cool thing!