What is the extraction channel effect of espresso? What will be the consequences? The reasons for the channel effect of espresso

When extracting espresso, the more common problem is the unstable flow rate, which sometimes flows faster and faster, while this cup of coffee shakes and feels a little thin and the grease is lighter. In this case, the coffee pressed powder is "perforated".

What is "piercing"? When you finish the extraction, pull out the coffee handle and see that the surface of the pressed powder is uneven and there are some small holes, like this ⬇️

Seriously, it would be like this, ⬇️.

These holes are punctured by water during extraction, and when the hole is punctured, the resistance of the whole pressed powder to water is uneven, so more water will pass through these holes, so it seems that the flow rate will increase. And because the water through the hole does not fully extract the coffee powder, the whole cup of coffee becomes thin and the oil is light. Generally speaking, this phenomenon is called "channel effect". How to find the perforation phenomenon the bottomless handle is the easiest to find the perforation phenomenon. Let's take a look at the normal extraction situation and the extraction situation during perforation ⬇️.

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This is the normal extraction of coffee flow rate and oil distribution, we can see that the flow rate is generally uniform, not sometimes fast and sometimes slow, and the overall oil is orderly from dark color to light color.

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This is the extraction condition with the phenomenon of perforation. It can be seen that the flow rate of coffee liquid is faster and faster, and there are two jets. The place where the spray appears is the position of the perforation. It can be seen that the velocity of the perforation is much faster, and the color of the oil is lighter than that of other places. Why is there a perforation? There are three main reasons: uneven distribution of powder, too little powder and concentrated effluent. The uneven density of pressed powder is the high-frequency cause of perforation. When the density of pressed powder is different, water is easy to break through the places with low density and is easy to perforate. In order to solve this problem, the steps of distributing and pressing powder will be carried out before the coffee is extracted. The cloth powder is taken as an example to make the coffee powder roughly evenly distributed in the powder bowl so that the density between the powder layers is not too extreme. On the other hand, the pressing powder is to press the evenly distributed coffee powder into a cake so that it will not be washed away by the water.

Many friends know that cloth powder is needed to extract espresso, but most of the time they are making useless cloth powder, that is, the cloth powder is still unevenly distributed, and the perforation will still appear. The reason comes from not connecting the powder well with the handle, or trying to mix the coffee powder after connecting the powder, as a result, the powder layer becomes more and more solid. It is easier to distribute the powder evenly by pushing the coffee powder into a small mountain bag (high in the middle and low around), then put the powder distributor vertically on top of the powder bowl and rotate it several times. If there is no problem with the cloth powder, then the pressing powder only needs to be flattened.

In the case of a small amount of powder, the water distribution network is relatively far away from pressed powder, in the extraction, the surface of the coffee powder may be impacted by water and cause tumbling, the surface resistance is inconsistent, it is prone to perforation. So in order to avoid this risk, some friends will increase the amount of powder or change a smaller powder bowl.

The function of the water distribution network is to divide the strong high-pressure water column into uniform water flow, but if the water diversion network is blocked by some coffee residue powder, the water flow distribution is uneven, then the water flow distribution is uneven, and it is possible to break through the powder layer under excessive pressure on one side during extraction. In this case, it is also easy to see that the normal outlet state is that the water diversion network will spread the water flow evenly, forming 4-5 water columns. If the abnormal situation is to converge into a water column, then the water diversion network needs to be removed and cleaned.