Ask the Experts: What's the Difference Between Pressurized and Non-Pressurized Filter Baskets?
We sell several semi-automatic espresso machines (such as the Saeco Aroma or Via Venezia, any of the Brevilles or DeLonghis that feature a pressurized portafilter basket. This is a major functional difference from other machines, like the Rancilio Silvia or Rocket Espresso semi-automatic espresso machines, which have non-pressurized baskets similar to commercial-grade machines. In the photo to the right, you can see the physical difference between a non-pressurized basket (on the left) and a pressurized basket (on the right).
OK, so they look different -- but what do they do that's different? Well, we think it's all about forgiveness.
Pressurized baskets have an internal screen that filters the coffee into a small holding area with a single tiny hole in the bottom. The espresso collects in the holding area and then the machine's pressure builds in order to force the coffee through this hole. We consider these baskets to be more 'forgiving' because they allow for a wider variety of ground coffee -- since the coffee is in contact with the water longer, and is forced into a holding area prior to brewing into your cup, the consistency of the ground itself is not as important and you're able to pull a good shot regardless of the grinder you may have. It is a bit illusory, however, because the pressurization produces a 'fake' crema, not the result of fine espresso extraction, rather the result of aeration of the espresso as it is forced through the small spout.
Espresso machines with pressurized baskets are a great option for people with lower end blade or burr grinders that find their coffee grounds aren't as uniform as is necessary for higher end espresso machines...but they shouldn't expect that they'll be able to pull the high quality shots they could pull out of a non-pressurized basket.
Since non-pressurized baskets brew directly into the cup without forcing the espresso through a tiny hole, inconsistent or too coarse/fine grounds will result in poor shot extraction -- it won't be pulled in the correct time or have any crema. While there is a curve in learning how to pull shots with this type of basket, it's definitely worth the time, as your tastebuds will no doubt agree.