Espresso Extraction Standards: Coffee Quality and Filter Basket Performance Comparison

What is a Portafilter Basket?

A "portafilter basket" is a bowl-shaped component installed on a coffee machine's portafilter. Because it holds coffee grounds, people call it a portafilter basket. Since manufacturers typically include default portafilter baskets when purchasing coffee machines, most people don't specifically research them. The general understanding of portafilter baskets is that they serve only as a filter, similar to filter paper.

However, its function is not limited to this. If you've recently researched espresso extraction issues, you've likely seen this sentence: "Poor espresso extraction is mostly due to choosing the wrong portafilter basket." The implication of this statement is that portafilter baskets also affect espresso extraction. So the question arises: are there differences between portafilter baskets? And how do they affect extraction?

Don't know? No problem~ Today, FrontStreet Coffee will briefly explain how portafilter baskets affect espresso extraction!

Portafilter Basket Diameter

If you open any search software and search for portafilter baskets, you'll likely see the numbers "51" and "58." These numbers primarily refer to the currently popular portafilter basket/portafilter diameters. When purchasing coffee machines, besides considering the machine's functions, this value should also be factored into your purchasing decision.

Because different coffee machines' brew heads are compatible with different portafilter basket/portafilter diameters, and these cannot be changed, each coffee machine and its accessories must have unified, fixed diameters. When purchasing related accessories, you must buy ones with the same diameter, such as tampers, distribution tools, secondary shower screens, etc. Otherwise, they won't be usable due to incompatible diameters. It's worth noting that 51mm and 58mm are just two widely used diameters; other diameters also exist. Generally, smaller diameter portafilter baskets/portafilters are mainly used for home coffee machines or older models; while larger diameter ones are primarily used for commercial/mid-to-high-end coffee machines.

The diameter of a portafilter basket creates two effects: one is the surface area of the coffee puck. When the portafilter basket diameter is larger, the puck's surface area is also larger, and vice versa; the second is the puck thickness. With the same dose, the puck thickness in a larger diameter basket will be less than that in a smaller diameter basket. Both of these factors affect espresso extraction: the puck's surface area determines the amount of water contact area, while puck thickness determines the resistance level of the puck.

Portafilter Basket Capacity

As everyone knows, the amount of coffee grounds a portafilter basket can hold is limited. This is because you need to ensure that the tamped puck maintains a certain distance from the shower screen; being too close or too far will affect espresso extraction. Therefore, the amount of coffee used in each basket is limited to a specific range.

For example, the double basket currently used by FrontStreet Coffee has a capacity range of 18-21g, while a single basket's capacity ranges from 9-11g. This is just an example—there are many other ranges that FrontStreet Coffee won't list individually. However, because the portafilter basket's diameter is fixed, the basket's capacity affects its height. Among baskets of the same diameter, the larger the capacity, the taller the basket; the smaller the capacity, the shorter the basket.

In other words, when the portafilter basket holds more coffee, the puck thickness will be relatively thicker. And puck thickness affects the puck's resistance: when the puck is thicker, the coffee machine needs to apply more pressure for extraction. This sounds complicated, but simply put, among baskets of the same diameter and type, the greater the basket capacity, the thicker the puck, the higher the resistance produced, and the greater the pressure needed for extraction. This is the extraction effect brought by the difference in portafilter basket capacity.

It's worth noting that when the coffee dose becomes too low, the structure of the portafilter basket changes. For example, the single basket, often featured as a "negative example," requires changing the basket shape to increase puck thickness due to insufficient coffee dose. But this simultaneously causes frequent channeling, making single baskets an obsolete product of our time.

Portafilter Basket Hole Diameter and Quantity

Besides the basket shape affecting extraction, the diameter and quantity of the filter holes also impact extraction. When discussing this, we must mention the revolutionary "VST" in the portafilter basket world. Before VST appeared more than a decade ago, espresso machine portafilter baskets had a common design flaw: the filter hole diameters were inconsistent. Some were very large, others very small. This led to an awkward phenomenon: oversized holes allowed many fine particles to pass through, increasing the coffee's bitterness; while undersized holes were easily clogged by fine particles, preventing liquid flow. Therefore, espresso extraction conditions at that time were not optimistic. Then VST founder Vince Fedele accidentally discovered this problem and began developing high-precision portafilter baskets: the hole diameters were not only more uniform but also orderly arranged, allowing espresso extraction to become stable.

From this small anecdote, we can see that the impact of portafilter basket hole diameter on extraction is significant. Its size and quantity primarily determine the flow rate of coffee liquid. FrontStreet Coffee will give an example: when the basket holds the same amount of coffee with consistent grinding, the larger the basket's hole diameter and the more holes there are, the faster the coffee liquid flow rate and the less pressure applied during extraction; conversely, when the basket hole diameter is smaller and there are fewer holes, the coffee liquid flow rate is slower, requiring greater pressure. This corresponds to two extremes: fast flow and slow flow. The industry has given each a professional name: "high-flow baskets" and "low-flow baskets." By controlling the size and quantity of filter holes, they adjust flow rate and extraction pressure (which is why there are also pressure-boosting baskets with very few holes).

Conclusion

Above are the main differences between portafilter baskets. However, it's important to know that the opening statement, "Poor espresso extraction is mostly due to choosing the wrong portafilter basket," is not entirely correct. One blogger said it well: "Whether stir-fried food tastes good has little to do with the heat-conducting wok, because the wok is mainly responsible for heat conduction—the specific result depends on the chef." Different portafilter baskets certainly have different characteristics, but the differences aren't too significant, and the extraction logic remains the same. As long as we understand the fundamental logic of extraction, we can extract delicious espresso regardless of the type of portafilter basket used.

Important Notice :

前街咖啡 FrontStreet Coffee has moved to new addredd:

FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473