What's the Difference Between Single and Double Shot Baskets? What Does Adding a Shot Mean? What is a Shot? How Much is a Single Espresso Shot?

"Adding a shot" is a coffee strength option offered to customers in coffee shops. When we feel the coffee isn't strong enough or want to consume more caffeine, we can add an extra shot to the coffee we've already ordered.

One shot of coffee refers to a single espresso, while the term "Shot" is a professional term from the liquor industry, serving as a unit of measurement for alcohol. One shot equals one ounce, and one ounce equals 30ml. Originally, one shot referred to a 30ml single espresso extracted from 9-11g of coffee grounds. However, since extraction concepts have evolved, most coffee shops now define one shot as a double espresso extracted from 18-20g of coffee grounds.

Of course, many coffee shops worry that customers might not accept the intensity of four shots stacked together, so they use the original parameters to extract a double espresso and divide it into two portions. One portion is poured into the customer's coffee, while the other is either discarded or consumed by the barista. This was also a common practice among merchants before specialty coffee became popular.

But for friends who have coffee machines at home, they know that besides double portafilters, there are also single portafilters. Early extractions of 9-11g of coffee grounds used this type of portafilter, which look like this↓

The Question of Single vs Double Portafilters

So, here comes the question. Why would coffee shops rather extract two shots than use a single portafilter to extract one shot? Wouldn't this better save resources and costs? The reason is quite simple - it's precisely because of advancements in extraction concepts that we've changed our extraction methods, but single portafilters couldn't meet today's extraction standards, so they were gradually phased out. So today, FrontStreet Coffee will share why single portafilters have been "eliminated"!

Single Shot Portafilters

Let's first look at the differences between single and double portafilters in appearance:

The common double portafilter has an overall cylindrical appearance, and the extracted coffee puck, when knocked out, will also be a neat, circular block.

The single portafilter, however, is somewhat irregular, mainly featuring a double-layered inverted cone structure. The upper rim has the same diameter as regular portafilters, but since single shots use half the amount of coffee grounds as double shots, the lower part of the single portafilter is designed with a narrowing shape. This allows the rim to remain consistent while maintaining the same maximum thickness of the coffee bed, which can provide more space for extraction.

But! Extraction isn't as simple as one might imagine. The application of single portafilters isn't as straightforward as dividing 20g of coffee grounds in half and using one portion, as demonstrated in FrontStreet Coffee's extraction experiment below.

FrontStreet Coffee uses 20g of coffee grounds as the standard for double portafilter extraction, yielding 40ml of coffee liquid in 30 seconds, with a measured concentration of 11.28% and a calculated extraction rate of 21.89%. When using a single portafilter for extraction, the standard is 10g of coffee grounds, yielding 20ml of coffee liquid. The flow rate will be slightly faster. Crucially, during the extraction process, multiple splattering effects occurred, which is essentially channeling.

It took 18 seconds, with a measured concentration of 8.55% and a calculated extraction rate of 18.12%. As you can see, this extraction rate is significantly lower. If we want to increase the extraction rate and concentration of the single portafilter to match the data from the double portafilter, we must either add more coffee grounds or adjust the grind to be finer, thereby giving hot water sufficient extraction time.

This undoubtedly increases costs for merchants, including material costs for grind adjustments and time costs. Through multiple extraction rounds, FrontStreet Coffee found that 13g of coffee grounds were needed to make the various aspects of the espresso (concentration, extraction rate, taste) closely resemble the taste of espresso extracted from a double portafilter. The reason for such significant differences is precisely due to the structure of the portafilter.

Structural Differences and Their Impact

As you can see, the double portafilter has a straight cylindrical structure, which means that whether tamping or being subjected to pressure during extraction in the coffee machine, every part of the coffee bed can bear force evenly. Therefore, during extraction, hot water can more evenly extract most of the coffee bed.

The single portafilter, however, is different and has more limitations. It not only needs to maintain the same upper rim diameter as other portafilters to fit the group head but also compresses the bottom space and changes the bottom structure to ensure the thickness of the coffee layer. Such a portafilter, wide at the top and narrow at the bottom, will cause the pressure around the edges to inevitably be higher than the pressure at the center at the same level, whether during tamping or extraction.

Then, during extraction, hot water will preferentially extract the center portion, followed by the edges. When hot water penetrates to the lower layer, it will again concentrate on extracting the center. This is a completely different extraction state compared to regular portafilters, making uneven extraction very likely, which then leads to channeling. We can fully observe this from the extracted coffee puck and the "residue" in the portafilter.

Conclusion

Therefore, when extraction concepts evolved and iterated, the disadvantages of single portafilters were completely exposed. Unable to keep up with the times, they gradually fell out of use as time passed.

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Important Notice :

前街咖啡 FrontStreet Coffee has moved to new addredd:

FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473