Espresso: The naked portafilter at Blue Bottle Coffee
I was at Blue Bottle Coffee at the Ferry Building. I tried the machiato, and the "Gibralter," which is a super-short cappuccino/latte (photos #1 and #2). Their espresso is excellent: rich and complex.
I noticed that they use a naked portafilter with their espresso machine (see photo #3), which does not have spigots: the espresso comes out the bottom of the bare mesh. The barista explained that by using a naked portafilter, they can clearly see the process of extraction, and maintain perfect quality control. It's reflected in the quality of the espresso. Here is a write-up I found on the web that explains the benefits of a naked portafilter:
I'm interested to know if other cafes in the Bay Area use a naked portafilter, since I'm always on the search for baristas who are obsessed with quality and consistency.
Yes, just about all the "third wave" shops use the bottomless portafilter The original idea was that the espresso would touch less metal and therefore not lose as much temperature. In practice, besides being cool, it is a good teaching aid. You will see any imperfection in the grind and more importantly the distribution of the puck. Any channeling will be obvious where in a traditional set up not so.