A portafilter (or group handle) attaches to the grouphead of semi-automatic and piston-driven espresso machines, and carries a tamped puck of coffee grounds within its basket. It is usually made of brass for better heat retention, but often is made of aluminium to save costs. The portafilter is attached to a plastic or wooden handle.
The portafilter forms a seal with the espresso machine’s gasket, and directs high-pressure hot water through the coffee puck. After-market retailers also sell bottomless portafilters that minimize the espresso‘s contact with any metal. A bottomless portafilter is one tool baristas use to analyze the quality of the coffee grind. Visually inspecting the espresso flow during the extraction allows for the detection of “channeling”. Channeling is the condition in which water is able to pierce a hole in the espresso puck during the brew process leading to uneven extraction.
The portafilter holds the filter basket, which serves as a filter during the extraction. The filter basket also dictates the pressure in the coffee puck during the shot extraction. The portafilter can accommodate various basket sizes from a single shot, to a triple espresso shot.
A good portafilter is a great tool for making the perfect espresso.