How to use the tutorials to explain the principle of the drawbar coffee machine and how to extract coffee

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Although we have a certain understanding of the pressure change and taste, it is impossible to do a comprehensive variable pressure experiment because of the time constraint. Moreover, it is best to have a systematic theoretical framework for comprehensive testing. And this framework is a series of articles on extraction framework that I have completed one after another. Because it involves the problems of extraction efficiency and extraction uniformity.

In addition, transformer is undoubtedly the most widely publicized topic of coffee "high-tech" nowadays. But unfortunately, there are not many people who understand the transformer, and few people can make good use of it, make it in cafes, and have good replicative coffee. So, frankly speaking, apart from the unusual construction of the machine, I am not very interested personally.

Recently, however, it took some time to learn about the equipment, especially the drawbar coffee machine. In fact, the pull rod machine in the late 1940s was a coffee machine with reasonable variable pressure and replicability. Here, you can refer to the introduction of the pull rod machine on the official website of kees. Although its operation mode is more or less different from that of other rod pulling machines, the basic principle is still the same.

Generally speaking, the pull rod coffee machine is like this during the extraction, (to help understand, and is aimed at the pull rod machine, not the unique function of kees. I changed the description a little bit. )

1. When the lever is in the highest position. There is a low-pressure pre-immersion function. Let the water slowly infiltrate the coffee powder under low water pressure. This is similar to hand steaming, which releases carbon dioxide. (for details, see my other diary for uniform extraction) it is worth noting here that the diameter of the cylinder of the tie rod is the same as that of pressed powder, which also promotes the effect of uniform extraction.

two。 When the first drop of coffee liquid is dripped, the pull rod is pressed down to the low position, the 9 pressure extraction begins, and as the pull rod rises slowly, the 9 pressure is slowly and smoothly over to 5 pressure. For the extraction taste, as the extraction efficiency decreases, which is similar to braking early, we can have better fault tolerance because we have more time to prevent coffee from being overextracted. And the material of the drawbar machine is copper, so the thermal insulation performance is better, which prevents the heat damage and ensures the stability of the temperature. When the pull rod returns to its original position, the extraction pressure returns to 0.

This kind of pressure curve has two meanings.

1. It is no longer a constant pressure of 9, taking into account the freshness of coffee pre-leaching, and finally to prevent over-extraction. This kind of attempt, which I have simulated on my own machine, can indeed get a cleaner taste of coffee.

two。 It's just that I simulate for this curve, which requires a lot of consideration. Look at the time, read the seconds, extract for a period of time, and then pull it back to the low level. But a "pull rod" action of the pull rod coffee machine can be fully taken into account.

The lever coffee machine is also beautiful, and for me, it stole the limelight from speedster. The article points out that coffee shop baristas use drawbar machines to make coffee, the feeling is completely different. No wonder 90% of the coffee shops in Naples use rod drawers.

Of course, new coffee machines, such as the lever coffee machine La Marzocco, already have a pressure curve storage function. However, as far as I am concerned, the pull rod mode is really very easy to use. And our current stress curve, although more intelligent, but the ultimate goal, at least I think, is not to give extraction a lot of options, but to stabilize the production of a good cup of coffee.