How to find the right grinding scale for hand-brewed coffee? How to use the No. 20 screen? How to calculate the pass rate?

The grinding scale of coffee beans is a difficult parameter to grasp. Different bean grinders have different scales, and different people have different views on particle size. Therefore, in the absence of a unified description, people who want to share grinding parameters can only use analogy to describe their particle size, such as coarse sugar, fine sugar, flour and so on. Then, a careful friend saw the clue of Qianjie and asked: "Qianjie Qianjie, why do you always use the pass rate of screen?"

As mentioned earlier, everyone has their own understanding of particle size. This leads to the fact that the coarse sugar he said may belong to the state of fine sugar in the eyes of another person. Then it is difficult to accurately convey the degree of grinding to each other! When there is a deviation in communication, then even if the same bean is used, it will have a different taste due to different grinding parameters. As a result, Qianjie used this "screen calibration method"! Although it has some limitations, it can ensure that friends can use roughly the same degree of grinding when cooking, minimizing the differences between each other! So let's share how this screen should be used in Qianjie today.

Screen calibration method first of all, we need to understand that any bean grinder, regardless of its price, no matter how fine it is, the coffee particles it grinds are not absolutely uniform! What do you mean? It is in the grinding of coffee beans that a wide range of particles such as 0.1mm~1mm may be ground at the same time. We cannot control that it can accurately grind all the particles to a uniform size, so all we can do is to keep most of them in the ideal range.

And this ideal range, preferably within the 0.6~0.85mm range. A small number of other particles, even outside this range of particle size, will not have much impact. After knowing this premise, we can begin to learn the screen calibration method! First of all, we need to prepare a 20-size screen, which can be bought on all major shopping platforms at a very suitable price. However, it should be noted that sellers often split the screen for sale, so try to choose an integrated screen instead of a single screen, otherwise it will be more troublesome to use.

The pore diameter of the sieve is 0.85mm, and its main function is to separate coffee particles larger than 0.85mm and less than 0.85mm. And the value we want to take is the amount of powder that can pass through the filter. Qianjie recommends that the thickness of hand grinding is 80% of the pass rate of the screen, that is, in a serving of coffee powder, 80% of the powder can pass through the screen. The calculation rate of the screen is very simple, the specific operation is to take 10g coffee beans, and then choose a grinding scale that you think is appropriate to grind it! After grinding, put it into the sieve and shake it horizontally until there are no particles falling. (it is expected that the time will be about 5 minutes, a little waste hand! )

Then we weigh the amount of powder that has fallen and divide it by the total amount of powder to get the screening rate! For example, if the amount of powder dropped is 7g, then its over-screening rate is 70%. If you want to achieve 80% over-screening rate, you need to fine-tune the grinding degree and re-measure the over-screening rate until you reach the target.

The reason why the over-screening rate should be controlled at 80% is that this screening rate can be applied to most coffee beans with a high fault tolerance rate, even if their baking degree is different, it can also avoid most of the overturning sites (such as blockage, or water too fast). However, it is mentioned in the front street that it has certain limitations! The limitation is that the pass rate of the screen is set according to the quality of the bean grinder! If it is some poor quality, fineness of bean grinder, then the grinding particles will be very uneven. Not only have too much fine powder, but also have too coarse particles! If this is the case, Qianjie suggests that the cooking time should be used as a reference for the degree of grinding! Taking the three-stage cooking in the former street as an example, when the cooking parameters were normal (15g powder, 1:15 ratio, grinded properly), the cooking time would be about 1 minute 50 seconds to 2 minutes 10 seconds. If the time is not in this range, it means that the grinding is too coarse or too fine, and then we adjust the grinding according to the judgment.

Of course, not only the time, but also the state of the powder bed can be observed. Under normal cooking, the sedimentation of the powder bed is a process of uniform decline, if the water level drops too fast, then it is too rough; if the drop is too slow, clogged, and the appearance of the powder bed is muddy, it is the cause of grinding too fine! At that time, we need to make corresponding adjustments, so that the grinding can return to normal and make delicious coffee.

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Front Street Cafe

No. 10 Baoqian street, Yandun road, Dongshankou, Yuexiu district, Guangzhou, Guangdong province