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, and is attached by 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 and the evenness of the extraction and allows for a visual check of "channeling" or the condition in which water is able to pierce a hole in the espresso puck during the brew process leading to poor extraction. Often, baristas use knockboxes to store their spent espresso grounds after they have pulled a shot.
For example, if your coffee tastes a bit salty or sour, the grounds are under-extracted, which can be remedied by a finer grind. But what if only some of your grounds are too coarse, and others are too fine – and maybe some are just right? Having uniform grind size throughout your brew basket makes it easier to isolate and adjust this variable in order to get the level of extraction you want. The only way to achieve that is with a burr grinder. Miller — as well as a handful of our other experts — recommends the Barazata Encore Coffee Grinder ($129).
Since semi-automatic espresso makers require you to dose the coffee yourself, grind and pack it, they give the brewer more control. You can tinker and master the art of making espresso. You can learn to pull the perfect shot. Still, fully automatic machines are a good option for someone who wants quality espresso at home, but wants to put in less effort (and skill). According to our expert from Students of Coffee—and our own online research—a semi-automatic machine is the best way to make espresso.
If you’re ready to drop serious money on a high-quality espresso machine that produces smooth, complex shots, our pick is the Rocket Espresso Appartamento Espresso Machine. The machine lets you cycle quickly between steaming milk and pulling espresso: It uses a heat exchanger, rather than the more typical thermoblock, which means that the Rocket’s boiler heats all the way up to milk-steaming temperatures when you first turn it on. When you’re ready to pull shots, the heat-exchanger sends a burst of cool water through a copper tube in the boiler, bringing the temperature briefly back to espresso-friendly levels before heating back up.