A friend shared his recent distress with the front street, that is, when he was making coffee, he found that the drain was a little clogged, and the flavor of the drink was also a little complicated, and the flavor was not clear enough. So he bought a sifter to sift out the fine powder, and the result was that the water was not clogged, but the taste was very dull. This completely confused him.
Fine powder is a double-edged sword
Fine powder here refers to "very fine powder", which is about the same thickness as the grind of espresso, less than 250 microns. No matter how expensive the grinder, it is inevitable that the ground coffee will inevitably appear very fine. But a good grinder will produce less fine powder when grinding, and a grinder with poor grinding quality will produce more fine powder when grinding.
Since these powders are much finer than normal hand-poured-over particles (600-800 microns), the flavor compounds are released faster than those coarser than the coarser coffee powders during extraction. So in essence, the extraction rate of the fine powder will be higher than that of the coarser coffee powder. Because of this uneven extraction at the microscopic level, the flavor of the coffee is richer and the layering is more obvious.
Of course, this has to be done when the fine powder does not occupy a lot of the total powder, and some of the fine powder is not enough to subvert the whole cup of coffee. When the amount of fine powder is large (less than 250 microns of coffee powder accounts for more than 10% of the total powder), the first problem that arises is that the fine powder will clump together and block the drain hole. Causes slow launches. Secondly, more fine powder and longer extraction time will make the coffee have a bitter taste. Essentially, this "uneven extraction" is out of balance. Sieve powder
In the face of this phenomenon, the first and foremost method is to replace the grinder with better grinding quality, but obviously this method has a high budget and generally needs to be considered twice. Another alternative is to purchase a fine powder sifter, after grinding into coffee powder, the fine powder is artificially removed with a sieve, which can also solve the troubles caused by fine powder.
But at the same time, it also loses the surprise brought by the fine powder, because the artificial sieve powder sifts the fine powder too clean, the cleanliness of the brewed coffee will be relatively high, but at the same time, there will be a watery and dull flavor performance.
Sometimes, sifting out the coffee powder will make the brain can't calculate, Qianjie is fortunate to meet a case, a friend weighed 15g of coffee beans, ground them into coffee powder and sieved out the fine powder to brew, originally used a ratio of 1:15 for water injection, in fact, 225ml of water was also injected, but after he injected it, he still didn't remember that 15g of coffee powder is less than 15g after sifting off the fine powder. Of course, this is just a very fortuitous case, but it reflects that the more things that are done, the more uncertainties there are.
Add the fine powder back to the brew?
In order to solve the problem of clogging the fine powder while avoiding the dull flavor, many people have expressed his whimsical ideas. Among them, the sieved fine powder is re-added for extraction, and the timing of the addition is very important. The operation is like this, first use a sifter to sift out the fine powder, and then brew normally in sections, when the last section is ready to be filled with water, pour the fine powder into the filter cup and inject the last section.
In fact, this practice avoids the bitter taste caused by the extraction of fine powder for too long, which can not only retain the flavor provided by fine powder, but also avoid the phenomenon of fine powder blocking the drain hole. (What's more important is not to waste ground coffee).
Use the sifter wisely
It is not that the water is slow to sieve the powder, usually the need to use the sieve powder, is the phenomenon that the powder bed is all mud-like after the water is blocked, and these are obvious problems of too much fine powder.
Sometimes the slow draining is caused by some habits, for example, using an electric grinder, there is always some fine coffee powder stuck to the powder outlet at the end, and after patting these coffee powders into the powder cup, they are at the top, and when they are poured into the filter cup, they become at the bottom, so that they can block the drain hole without a lot of fine powder. 
Alternatively, shake the cup to layer the coarse and fine powders. If you look closely, the structure of the freshly ground coffee powder is that some relatively large particles of coffee powder will stick to the powder layer around it. If you don't shake it, it will separate the coarse powder from the fine powder, and the fine powder will hold itself together, which will make the water flow slower.
Or, in the water injection after steaming, the water is usually injected in a circle from the center to the outside, so that the water injection also pushes the powder layer to the surrounding area to form a powder wall, and the main fine powder is pushed to the edge of the filter paper in this way, which will not hinder the speed of draining. If the fine powder attached to the powder wall is washed into the powder bed, it will also cause slow draining.
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