Dialing In: Filter Baskets

One of the easiest ways to make better espresso at home is to switch out the the stock basket that comes with your machine to a precision basket. But why? What is that little piece of equipment actually doing? 

RESISTANCE = ESPRESSO

A properly extracted espresso is the result of pushing water through a bed of coffee at high pressure for a specific amount of time- the coffee provides resistance, forcing the water to stay in contact with the grounds and magically transform into sweet, sweet espresso. The coffee bed is what makes up most of that resistance.

But don't overlook that filter basket! The quality of those tiny holes also affects resistance, and can make a big difference in the extraction of your espresso. 

WHO IS VINCE FEDELE?

A couple of factors brought us the precision basket: espresso started changing from the traditional Italian 14 grams of coffee to larger doses- 16, 18, even 24 grams of coffee in the same size baskets. The other factor is Vince Fedele. 

Vince Fedele of VST is the creator of tech innovations such as FireWire and the first external hard drive, smart chargers and other computer related peripherals- and also someone deeply interested in espresso and improving brewing technique. 

Sometime after working with Apple, Fedele developed a high fidelity fingerprint scanner for the FBI (it didn’t work out with the FBI, but we got precision baskets out of it, so it’s not a total wash). One day, frustrated by the inconsistent extractions he was getting, even in his very controlled set up, he ended up putting a basket on the scanner to see what it looked like up close. 

It turns out what looked orderly to the naked eye was actually a wildly different story up close. Holes of different shapes and sizes, some with burrs still attached, some only partially cut, distributed over the surface of the filter. Scanning another filter that was the same model revealed the two baskets to be completely different. 

An irregular basket meant that even with everything else dialed in, the coffee bed would have different amounts of resistance all over. Bigger holes let more espresso through, while smaller or not fully punched holes would let less through, resulting in channeling, uneven extraction and sad coffee (and sad baristas).

This discovery inspired Fedele to develop manufacturing processes to make baskets with uniform perforations, and were also were "tuned" to have resistance proportional to different doses for more accurate and consistent extraction.

Larger dose = deeper basket, more perforations

Smaller dose = more shallow basket, less perforations*

*incredibly simplified explanation. 

Since the introduction of precision baskets, more features have been developed in the quest for the perfect shot, including: 

- Ridgeless precision baskets, with completely smooth sides. This allows the spent puck to knock out cleanly (some people also say the smooth sides help promote a more even water dispersion than a ridged basket. Maybe this is true.)

- Some filters feature a convex surface to encourage flow out of the center of the filter. 

- Nanotech coatings, a super slick coating over the surface of the basket that can reduce coffee grounds and oils sticking to the perforations. 

You can check your filter basket by holding it up to the light and looking at the holes- if you see that they are different sizes, unevenly spaced, or that some of them are partially blocked, it's a good time to invest in a precision basket. 

PRESSURIZED FILTER BASKETS

Sometimes called “Dual Wall” baskets, these look like a regular filter basket from the inside, but from the outside, only one tiny hole is visible. This is to allow for the use of pre-ground coffee (which is more coarsely ground). Because the coffee can't provide the resistance necessary to make espresso, the single hole does all the work instead. 

The extraction is watery, less sweet, and aerates the coffee to create a lot of weird, fluffy pseudo-crema. If you’ve invested in a good grinder, it’s best to skip these baskets entirely. 

WHAT KIND OF PORTAFILTER SHOULD I USE?

Standard commercial portafilters are 58mm, and any 58mm filter basket will be compatible with those handles. Machines that use a 54mm portafilter will use a 54mm filter basket. 

However, depending on the height of your basket, you may not be able to use a spouted portafilter, so keep that in mind when choosing a filter basket. Something that’s meant to hold 22 grams of coffee may be too tall to fit into the portafilter, so you can either use a smaller basket, or a bottomless portafilter. 

One of the great pleasures of using a bottomless (or chopped, or naked) portafilter is watching the espresso flow from the bottom of the basket. You can also use that information to evaluate your extraction and see if you need to adjust anything. 

Another factor to consider is that you don’t want to buy a smaller basket than what you usually dose, but you can always put a smaller dose in a larger basket (the puck will just be a little sloppy). 

THE TAKEAWAY

Espresso is a world full of adjustments and tweaks, and a precision filter basket is the quickest, easiest way for you to improve your home espresso bar. They control a variable that makes a huge difference in the quality and consistency of your shots, and allow you to concentrate on all the other factors you need to consider as you aim for that perfect espresso. Try one and taste the difference!