[contrast] is it better to have a powder hammer flat bottom or a thread? How strong is the powder pressing of espresso?

While watching the barista making espresso, the barista quickly picked up the coffee powder, poked it back and forth on the powder bowl, then took out a "big seal" and covered it in the powder bowl, and quickly buckled the brewing head to extract the coffee.

Why press it before you boil the head on the buckle?

① prevents the channel effect and makes the coffee extraction more uniform.

After laying the powder, the gap between the coffee powder particles may still be uneven, and the loose powder layer is easy to be washed away by the hot water of 9bar during extraction, forming a channel effect. The concrete performance is that the coffee liquid gushes and spurts during the extraction.

The compacted powder layer can make the coffee powder more dense, reduce the gap between coffee particles as much as possible, and reduce the possibility of channel effect.

② prevents coffee powder from sticking to the head and burning it.

If there is no filling and pressing pressed powder, then buckle directly to the brewing head, and the coffee powder on the surface of the powder bowl will stick to the water diversion net and be scorched by the hot brewing head. Then the extracted coffee will have a bitter taste.

Powder pressing is also a skill.

In addition to compacting the pressed powder, the most important thing is to flatten the pressed powder. Imagine that if the surface of the pressed powder is uneven, the left is low and the right is high, that is to say, the thickness on the left is thinner than that on the right. In this way, the water is very easy to break the weak side, resulting in uneven extraction.

① flattened pressed powder

The two most important points to flatten pressed powder are the pink hammer and posture. The powder hammer is the thing like the big seal, the most important thing to choose the powder hammer is the matching degree with the powder bowl, it is needless to say that the powder hammer caliber is larger than the powder bowl caliber, if it is less than the powder bowl caliber 2mm will cause the coffee powder on the edge can not be pressed down, which will naturally affect the extraction.

The posture of pressing powder is also very fastidious. When filling, the powder bowl should be horizontal and parallel, the palm of the hand should hold the handle end of the powder hammer, the tiger mouth of the palm is facing down, and the thumb and index finger should hold the hammer end of the powder hammer. When filling, the elbow, forearm, powder hammer and powder bowl form a straight line perpendicular to the horizontal. When filling, force is sent vertically, direction down, and coffee powder is compacted at once.

The strength of ② powder pressing

As for how much strength it takes to press the powder, some baristas seem to use a lot of strength, while others just press it gently. In fact, no matter how hard you use to fill pressed powder, it is not worth mentioning under the extraction pressure of 9bar.

When La Marzocco designed the Swift automatic filling device around 2000, they did extraction experiments with forces ranging from 2 pounds to 30 pounds (about 15kg). It is found that no matter how strong the force is, there is almost no force at the bottom of the pressed powder. Therefore, the strength of the powder has little effect on the extraction of espresso, as long as the powder is pressed tightly.