History
The first whispers of the bottomless portafilter appeared rather recently when, in 2004, Barista Guild of America cofounder and coffee specialist Chris Davidson developed a bottomless portafilter with some colleagues to see what its brewing capabilities might be.
In French, it's also called ‘porte-filtre sans fond’, which means ‘portafilter without a bottom’. This type of filter allows baristas to brew espresso more precisely than with a spout-equipped portafilter. You can see whether there's channelling, if the grind is right, or if the coffee was incorrectly pressed.
Other than the ability to observe the espresso, bottomless portafilters also allow for conserving all the crema, rather than losing some of it when transferring between spouts. This turns out to be quite practical for latte art, but it also improves the coffee's overall taste.
Bottomless portafilters are much easier to clean than their spouted relatives. No brushes needed, just a good sponge will suffice. It also provides more space under the brew group, which allows for using taller glasses.
