The Lowdown on Portafilters

What is a pressurized portafilter? How about a non-pressurized portafilter? Is one better than the other? What about those bottomless portafilters — are they necessary or just a random geek accessory?

Gail breaks down the intricacies of one of the most essential elements of an espresso machine — explaining how they work, why you would want one type over another and what purpose, if any, bottomless portafilters have.