What is the difference between a single flour bowl and a double flour bowl? Is 1 shot coffee a single espresso or a double?

When buying a coffee machine, a single powder bowl and a double powder bowl are usually included, so that we can switch between them according to different needs.

The limited amount of powder used in a single bowl is 9 - 11g, which is used to extract a single serving of espresso; while the limited amount of powder used in a double bowl is 18 - 22g, which is used to extract double espresso. Domestic coffee shops usually use double powder bowls, that is, 18 - 20g of coffee powder is used to extract 36 - 40ml of coffee liquor. When the customer feels that the coffee is not strong enough, he can ask the barista for a "shot" request, that is, adding one espresso/single espresso to the original.

Logically speaking, at this time, baristas should directly use a single powder bowl to extract a single serving of espresso for production. But in fact, very few coffee shops do this. Basically, you either directly use the double espresso as one serving, or you use a double powder bowl to extract the double espresso and pour half of it out, and the remaining half will be poured out or drunk by the barista. The former is due to changes in the extraction method, but the latter puzzled many friends, so they asked Qian Jie: "Why would people rather dump half of the concentration than use a single powder bowl to produce it? "It's simple, because espresso extracted from a single powder bowl is difficult to meet our current requirements, both in terms of taste and stability.

What is the difference between a single flour bowl and a double flour bowl? We can see from the picture that the biggest difference between a single flour bowl and a double flour bowl lies in their shape. The double flour bowl is a cylindrical structure, the whole body is vertical to the end, and the powder cake that is knocked out after the extraction is also a regular cylindrical shape.

The single-serving flour bowl has an inverted cone shape and is divided into two layers. The upper layer has a larger diameter and the lower layer has a smaller diameter. The reason why this design is made is to allow a small amount of coffee powder to be fully extracted!

The reason why the diameter of the upper layer of a single powder bowl is relatively large is that it needs to match the diameter of the brewing head so that the powder bowl can be successfully inserted into the brewing head. The reason why the lower layer is designed to be folded is that a single powder bowl can use less powder, only half of that of a double powder bowl. If it is designed to have the same structure as the double powder bowl, then the thickness of the powder bed will be thinner, which will reduce the amount of coffee powder that hot water comes into contact with during extraction, and the extraction efficiency will be less high. Therefore, the single-serving powder bowl can be designed to increase the thickness of the powder bed, so that a small amount of hot water can contact enough coffee powder for adequate extraction.

In other words, the function of a single powder bowl is to use a small amount of coffee powder to extract a small amount of coffee liquor, and then this cup of coffee will have the same concentration and extraction rate as the coffee extracted from the double powder bowl. However, most coffee guys, including Qianjie, found through experiments that the extraction of a single powder bowl is not as simple as everyone imagined. The following is an experiment conducted on Qianjie, which you can refer to.

Here, Qianjie uses two powder bowls to extract an espresso. The coffee beans used are the Qianjie classic Italian blend in the Qianjie bean list. Then, we measure and taste them to see if the taste and concentration of the two are consistent with what everyone imagined. The amount of powder extracted by Qianjie using double powder bowls is 20g, and the extracted espresso liquor is 40ml. The use time is 30 seconds. The measured concentration was 10.52%, and the extraction rate was 21.80%. The taste is expressed by chocolate, butter, nuts, and caramel. The taste is balanced, the taste is solid, and the finish is long.

Then there is the espresso extracted from a single powder bowl. The amount of powder extracted with it is 10g, and the coffee liquor extracted is 20ml. The extraction time will be much less than that of a double powder bowl, which is 21 seconds. The concentration was then measured to be 8.21%, and the extraction rate was 17.02%. The taste is not very pleasing, and then the flavor is not so outstanding. The taste is thin and the finish is not very long. Obviously, this is a manifestation of insufficient extraction. It can be seen that the difference between the two is very big. If we want to use a single flour bowl to extract the same taste and concentration as the coffee extracted from the double flour bowl, we can only refine the flour or increase the amount of flour. But the former is not realistic for a coffee shop. After all, you can't constantly adjust and grind it back and forth for a guest's shot;

Although the latter is relatively simple, it will increase costs simultaneously. Qianjie also conducted corresponding tests and found that under the condition of unchanged grinding, a single serving of powder needed to use more than 12.5g of powder to extract the same concentration and taste as those extracted from double powder bowls. But the cost increase mentioned here on Qianjie is not just as simple as the increase in powder quantity, but also the instability in extraction. The stability of extracting coffee with a single flour bowl is very low, which is why coffee shops would rather use double flour bowls to extract one more serving of coffee than use a single flour bowl-the extraction of a single flour bowl is not stable enough.

Why is the extraction from a single powder bowl unstable? The reason why Qianjie introduced the structure of the two powder bowls in detail in front is to pave the way for the explanation here. That's right! The reason for the instability of single powder bowl extraction lies in its powder bowl structure. Qianjie mentioned earlier that the structure of the double flour bowl is a straight column, so this makes the forces on each part of the coffee machine relatively uniform when distributing powder, pressing powder, and when extracting under pressure. This will make the extraction more even. The single-serving powder bowl needs to maintain a uniform diameter and at the same time allow the powder layer to have sufficient thickness, so a two-layer structure is designed. It is this structure that makes it difficult to uniformly apply the force to each part, whether during powder pressing or extraction. Especially when the amount of powder is large, the pressure on the four sides will always be higher than the pressure at the center of the same level. What does it mean? That is, when we fill coffee powder, the coffee powder around us will be compressed more firmly than the coffee powder in the center. This then leads to hot water preferentially/intensively extracting the coffee powder in the center during extraction, causing uneven extraction, which is the so-called channel effect. So basically, it is difficult for us to knock out a complete powder cake when using a single powder bowl. Because the forces applied to each part are completely different, the powder cake is difficult to form and is wet.

To sum up, you can know why coffee shops would rather use double powder bowls to extract one more portion of coffee than use a single powder bowl. It is because its extraction stability is low and we cannot guarantee that we can use it to extract an ideal coffee. Of course, it is also because China is now increasingly advocating that coffee extracted from double powder bowls is one serving of espresso, which naturally reduces the chances of a single powder bowl appearing.

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