Breville espresso machines, along with many other entry-level semi-automatics, come with 2 sets of filter baskets. 2 Pressurized, and 2 non-pressurized. Here’s how and when to use each type.
Non-Pressurized (single wall)
The pressure needed to brew espresso can be built in 2 different ways.
When you use a non-pressurized or “single walled” basket, pressure is built by the compressed puck of coffee.
This gives you full control over the extraction, as you can vary the flow rate by adjusting your grind size or tamping pressure like we saw in the dialing in article. This is the traditional way to brew espresso.
Pressurized (dual wall)
The dialing-in process can often be frustrating and inconsistent to beginner home-baristas, so companies developed the pressurized, or “dual wall” filter basket. A pressurized filter basket does not rely on the coffee itself to build pressure. Instead, it only has one very tiny hole for the coffee to exit from.
This ensures that proper pressure is built in the basket regardless of small tamping or grinding inconsistencies. We can see this in action by using our trusty bottomless portafilter.
With the non-pressurized basket, water pressure is built up evenly across the surface of the coffee puck,
and then exits evenly through the hundreds of small holes in the filter basket.
In comparison. The pressurized basket can be seen forcing all of the espresso out through one single hole.
Because of how pressurized filter baskets work, they also tend to create a coarser, more foamy crema.
When to use a pressurized basket
A pressurized filter should be used in 2 scenarios:
If you are using pre-ground coffee, or simply cannot grind fine enough to build the appropriate pressure, a pressurized basket will be your only option as it can effectively “help” you build appropriate pressure.
If you are simply exhausted by the dialing-in process and just want to get a drinkable shot of espresso for now. But you must promise to learn properly in the future!
In any scenario where you have full control over the freshness of your beans, and can grind as fine as needed to build pressure, a non-pressurized, single wall basket will produce a more balanced, and better tasting shot of espresso, and it’s worth it to learn how to use. A pressurized basket WILL allow you to get a drinkable shot when using suboptimal coffee, or simply with less effort dialing in, but it comes at a cost to both flavour, and texture.