What is the reason for the perforated spurt of espresso? The solution to the Channel effect of espresso

Friends who have played espresso machines should know the concept of "channel effect", even if they don't know it. As a novice disaster, we must understand it and solve it.

The "channel effect" channel effect generally refers to the uneven distribution of coffee pressed powder, causing pressurized hot water to break through the weakest part, and the water is inert and passes through the "channel" with less resistance. It leads to insufficient extraction of other coffee powder with high resistance. The most obvious manifestation in the appearance is that the "channel" causes coffee perforated spray, especially if the bottomless handle extraction is used, and the embarrassment is that the coffee liquid is sprayed on the bezel of the coffee machine.

If the shunt handle is used, the manifestation is uneven liquid separation, unstable flow rate and gushing phenomenon. After extraction, knock out the pressed powder and you can see that there is a perforation at the bottom of the pressed powder. The channel effect is accompanied by insufficient coffee extraction, water sensation, acidity / bitterness. What caused it? The first thing that comes to mind must be the problem of cloth powder pressing powder. when learning espresso, "Why do others have no problem with extraction, and you will pass as soon as you arrive?" That is to say, if the two steps of cloth powder pressing are not done well, it will indeed cause a channel. The purpose of the cloth powder is to distribute the coffee powder roughly evenly, and the pressing powder is to press the roughly uniform powder tightly. If these two steps are not done well, the channel is easy to appear. If you are using a cloth powder dispenser, push the coffee powder into a hill bag (high in the middle and low around), then place the cloth powder vertically on top of the powder bowl and rotate it several times without tapping the handle. This kind of cloth powder is better.

If there is no problem with the cloth powder, then the pressing powder only needs to be flattened, is there any requirement for strength? Yes, just press it tight, so much so that you feel like you can't hold it down. Don't worry, your little power is negligible in front of the 9bar at the time of extraction. The process of pressing the powder to buckle the extraction head should not lead to a major collision accident, as it is easy to separate pressed powder from the powder bowl, thus creating channels (not only the pressed powder perforation is a channel, but also the gap between pressed powder and the powder bowl).

The next reason may be insufficient powder and too fine grinding. The insufficient amount of powder is reflected in the distance between pressed powder and the brewing head. Under normal circumstances, an obvious excess of powder cannot be buckled on the head, and the amount that can be deducted is the surface of pressed powder and zero-distance contact with the water distribution network. This phenomenon can be first buckled on the handle, and then taken off to see if the water diversion network is glued with coffee powder. Another situation is that the amount of powder is too small, and there is a certain distance between pressed powder and the water diversion network, so that during extraction, the coffee powder on the surface may tumble, when the surface front is disintegrated, the surface resistance is inconsistent, and the channel effect can occur at any time. When the coffee handle is pulled out at the end of the extraction, you can see that the coffee powder on the surface is muddy, accompanied by perforation.

In general, the original powder bowl will have a concave warning line, after pressing the powder, pressed powder should not exceed this line, nor should it be too far away from this line.

The third is to check whether the water diversion network is blocked. Remove the water bowl and open the extraction button to produce a powerful water column. The function of the water distribution network is to separate the water evenly. Sometimes, during extraction, some fine powder will be poured in and stuck in the water distribution network, so the distribution of water flow will be uneven. During extraction, it is possible to break through the powder layer under excessive pressure on one side. It is necessary to remove the water distribution network and clean it regularly.