What is the difference in the ground thickness of coffee? How finely should the espresso powder be ground? How thick should the hand punch be?

The so-called extraction is to dissolve the flavor substances in the coffee by using water as a medium. Before extraction, we need to grind the coffee beans through a bean grinder, because only in this way can the flavor substances in the coffee be dissolved more quickly and more easily. And this is what we often call coffee grinding.

The priority of coffee grinding tends to be higher than other extraction parameters, because, as Qianjie said at the beginning, the fineness of grinding determines the speed of dissolution of flavor substances. According to scientific research, the surface area of coffee beans after grinding will be about 1000 times larger than before. When the finer the grinding, the more the surface area increases, and the shorter the linear distance of water from the powder meter to the center (affected by the cutter head); the thicker the grinding, the less the surface area increases, and the longer the straight distance of water from the powder meter to the center.

The increase in the surface area will give the coffee powder more contact with the water, and the straight distance to the center determines the time it takes for the water to penetrate into the coffee powder. In other words, the finer the coffee powder is ground, the more the surface area is and the shorter the straight line distance from the surface to the interior is, the faster the hot water dissolves the flavor substances, and vice versa. Therefore, no matter which method of extraction, the grinding of coffee beans tends to have the highest priority. We need to find the corresponding degree of grinding before we can start the extraction of a good cup of coffee.

What kind of grindness does different coffee extraction methods correspond to? I believe this is an answer that many friends need to know! However, because everyone uses different bean grinders and coffee beans, and because the degree of grinding can not be defined as a standard, we can only share with you according to a general scope. For example, coarse sugar grinding, fine sugar grinding, or flour grinding and so on.

As for which extraction method should be used and which grinding degree should be used, you can skip this article to explain in detail "Coffee Grinding reference". Or we can calculate the grinding thickness of the coffee directly from the average extraction time of the extraction method (of course, if there is a reference object)! The longer the extraction time is, the thicker the grinding degree will be, and the shorter the extraction time is, the finer the coffee powder grinding will be. For example, the extraction of espresso. We need to extract the coffee in about 30 seconds (for example, not necessarily), so the size of the coffee powder must be very fine! Only in this way can hot water dissolve all the flavor substances in the coffee powder in a short time.

But because the extraction method of espresso is pressurized and involves many factors, we can change the angle, such as hand coffee and siphon pot. The average extraction time of hand-brewed coffee is about 2 minutes, while that of siphon pot is less than 1 minute. Therefore, the coffee powder needed in the siphon pot must be finer than hand-brewed coffee. So by analogy, we can calculate the coffee powder grinding required by different extraction methods. (except for chic coffee such as Turkish coffee) then again, the reason why coffee grinding can not define a standard is very simple, because the size of the coffee powder we grind is not absolutely uniform! This is a point that is often mentioned in the front street.

Why are the ground particles not absolutely uniform? No matter what the quality of the bean grinder is, the ground coffee powder will not be absolutely uniform. There are both big and small ones. This has something to do with the characteristics of the beans and the cutterhead and motor of the bean grinder, and it is precisely because it is not absolutely uniform that the coffee we make is more layered. Therefore, we measure the grinding quality of a coffee powder according to its uniformity, the higher the uniformity, the better the grinding quality, and vice versa. (below is a 15g coffee powder ground with Ek43. The granules from left to right are large, medium and fine.)

No matter what kind of bean grinder uses what kind of cutter head, its grinding process will be accompanied by grinding. Rolling will promote the growth of fine powder, the more times of rolling, the longer the grinding time, the more fine powder (the particles from different cutters are also different). The existence of the right amount of fine powder helps to increase the sense of hierarchy, but at the same time it is also a double-edged sword! Too much fine powder will easily lead to blockage and unequal extraction. Therefore, we can know that a high uniformity of coffee powder is also important for brewing (the amount of fine powder accounts for 3% to 5% of the total powder).

How do the characteristics of coffee beans affect grinding? And the characteristics of coffee beans will also affect grinding, friends who have used hand grinding beans should be well aware of this. The feeling of grinding beans with different characteristics is completely different. Some beans are difficult to grind, others are finished with a few clicks. This is mainly affected by the roasting degree and density of coffee beans.

The deeper the coffee beans are roasted, the lower the density and the higher the brittleness of the beans, making it easier to grind. Because just like a cookie, we only need to break it in half with a little break. The lighter the coffee beans are roasted, the higher the density and the lower the brittleness of the beans, making it more difficult to grind. But we need to note that the higher the brittleness of coffee beans, the more likely it is to breed fine powder. Still take a cookie as an example, will there be a lot of small pieces after we break the cookies in addition to the two pieces of the target? This is because the cookies are more crisp. Applying this principle to the grinding of coffee beans is the same! Under the same grinding, the more crisp the coffee beans are, the more fine powder will be ground, and the overall grinding degree of the beans with low brittleness will be finer.

In addition to the degree of roasting, the treatment of coffee beans, planting altitude, bean species will affect the density of coffee beans. The higher the density of coffee beans, the finer the grinding we need, because the beans with high density are more difficult to extract, while the beans with low density need to be ground according to the degree of roasting and treatment. The deeper the roasted coffee beans, the thicker the grinding required because of the need to prevent the extraction efficiency from being too high. If the density is low because of the treatment, the adjustment of the grinding degree can be determined by the state of brewing and the taste of the coffee.

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