How does extracted espresso fill pressed powder? How much strength does it take to press the powder?

Sometimes, watching the barista's powder pressing action will also be a decompression thing! Because each barista has a different understanding of powder pressing, they will have different powder pressing actions.

Flattening the powder is already a consensus, because once the powder pressure is uneven, high on one side and low on the other, there will be a channel effect, which will eventually lead to uneven extraction. The barista's understanding of the powder is different: how much pressure it needs to put on the coffee powder to compact it. The baristas who feel that as long as the pressed powder is flattened and compacted by the two different schools of powder, usually only gently rotate the powder hammer, and then exert a little pressure, the whole movement comes down smoothly, gentle and elegant. Because they feel that no matter how hard it is to press the powder, the compactness of this piece of pressed powder is simply not worth mentioning in the face of the high-pressure extraction of the coffee machine.

And if it is a barista who feels the need to use great power to crush pressed powder, then you may see that his power is all on the arm of the powder press! Press the powder with the strength that seems to lift yourself up, as if to say that only one of the tables and coffee powder is flat! Because they think that the strength of our filling pressed powder can effectively control the flow rate, and the greater the force, the more uniform the extraction.

So, what kind of strength should we use to fill and press pressed powder? In front of the powder pressing experiment, two different kinds of grinding will be used, and two groups of experiments will be made, and each group will be filled with different pressure. See if filling coffee powder really needs to control the pressure! The bean mill used in the experiment is Galileo Q18, the amount of powder is 20g, the target liquid weight of extraction is 40ml, the scale of fine grinding is 1.5, and the scale of coarse grinding is 2.5. whether the strength of pressing powder can cause the change of extraction is evaluated by the extraction time.

(the picture on the left shows coffee powder ground with 1.5G scale, and the picture right shows coffee powder ground with 2.5D scale.) Fine grinding pressing powder compared to grinding 20g coffee powder with 1.5D scale, and after making cloth powder, we respectively used 1.5kg (conventional) strength and tried our best to fill and press pressed powder.

(the limit of the electronic scale is 3kg, so we borrowed the next-door neighbor's scale, using an all-out weight of about 9kg.) the 20g pressed powder filled with 1.5kg takes 30 seconds to extract the 40ml liquid, while the pressed powder which uses all-out pressure uses 33 seconds to extract, and in order to prevent the coffee powder from changing, the extraction time is still 33 seconds. It can be seen that the fine grinding of pressed powder will have the effect of extraction due to the change of the strength of the powder. The comparison of coarse grinding pressing powder is also after the distribution of powder, respectively, the use of 1.5kg and all-out different efforts to fill pressed powder. The results are surprisingly consistent, with the same time taken to extract 40ml liquid in 20 seconds (because it is thicker, so the extraction time is shorter).

Conclusion from the above experiments, we can see that the difference in the density of coffee powder will lead to a certain gap in the strength needed for pressed powder compaction. What do you mean? For example, the reason why our fine grinding experiments will produce different results due to the different strength of the powder, the reason is that the particles of coffee powder are smaller, and more strength will be used if we need to press it to a tight state! And the powder pressing strength of 1.5kg is obviously not enough, it needs more strength to press pressed powder to the most compact.

If we slightly increase our efforts to 2kg, then its extraction time will be the same as that of pressed powder, which is fully suppressed, because at this time, the two pressed powder slices are already the same compact degree, so the extraction time required will naturally be the same! And the rough ground pressed powder group well illustrates this point, because the gap between the coffee powder particles in pressed powder is large, and the pressure of 1.5kg is enough to make pressed powder very tight, so even if you use all your strength to fill pressed powder, whether the extraction result will be different from the strength of 1.5kg ~ so, we can appropriately adjust the strength of the powder needed between different thickness, the finer. The force exerted can be slightly increased by ~-END-

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