Water Temperature

Role

Temperature affects extraction, but in espresso the effect is entangled with puck prep, flow, and machine stability. Treat temperature as a tuning variable, not a rescue for poor distribution.

Adjustment

Higher temperatures can help extract dense light roasts; lower temperatures can soften harshness in darker roasts.

Caveat

Temperature effects can be less direct than expected because flow and puck mechanics also change the shot. ^{1This source is no longer available.}