What is the 'right' boiler pressure setting? wrote:Most home baristas set their espresso machine's pressurestat somewhere between 0.8 and 1.2 bar (measured at the top of the cycle) and then determine the flush amount to bring the group to the target temperature. I prefer the pressurestat setting on the lower end of the acceptable range because it slows the overheating of the water in the heat exchanger. The drawbacks are that it diminishes recovery time and especially steam production, some espresso machines to the point where they no longer can create microfoam well. But if you're preparing drinks only for yourself and perhaps a couple friends, the lower end of the boiler pressure range is easier to manage temperature-wise than the upper end. The barista's job is easier in the former case because the rebound time is long enough that the difference in brew temperature between a delay of 15 seconds and 25 seconds after the flush and the beginning of the extraction isn't dramatic. In contrast, a miscalculation of ten seconds risks producing an over-temperature extraction (very dark initial crema, black edges) for a pressurestat setting at the high end of the acceptable range.

The right boiler pressure for a prosumer machine is therefore the pressurestat setting that meets your drink preparation pace, and to some degree, your experience level. Finally, keep in mind that commercial HX machines in general are less influenced by the flush because of their heavier groups and larger heat exchangers. Manipulating the brew temperature outside of the "comfort zone" of such espresso machines by flushing requires more attention to timing the length of the flush and the rebound time, which compared to prosumer machines is very short (e.g., 10 seconds or less).

Fullsack wrote:...you would save yourself the pain of having to taste a lot of bitter coffee.