Grouphead
From Wikipedia, the free encyclopedia
A grouphead is a fixed component of an espresso machine. It is the receiver for the removable portafilter (or group handle). A typical consumer espresso machine normally has only one grouphead, while popular professional machines, such as those used at commercial coffee shops, can contain anywhere from one to seven.
During the process of extracting a shot of espresso, hot water is forced through the grouphead under pressure. The grouphead contains many holes that attempt to distribute the pressurised water evenly over the surface of the grinds in the portafilter basket and thereby achieve an even cross sectional flow.
[edit] E61
The E61 is a commercial grade grouphead, which when combined with the E61 manual lever and pressure relief valve comprise the E61 brew group. The E61 grouphead itself is distinguished by a large exposed disc shaped brass component which provides thermal inertia for temperature consistency during brewing using a heat exchange (HX) system to provide both brewing and steam from the same water reservoir. Before first use, a barista will typically utilize a "cooling flush" procedure to lower the temperature of the grouphead which is usually overheated by the superheated water in the HX-heated reservoir when idle. The E61 grouphead is often utilized without the manual lever and instead with a pump system in many commercial and semi-commercial machines.
