How fine is the coffee powder of espresso?

How fine is the coffee powder of espresso?

In the Italian coffee machine, the temperature value is mainly affected by the size of the boiler or heating block, as well as good heat conduction materials, there is an obvious difference between the toy machine and the professional Italian coffee machine. In general, many standard toy machines are equipped with small boilers (below 200ml) or small heating blocks, so it is difficult to achieve a stable temperature, and the temperature fluctuates greatly in the process of coffee extraction. The machines of many small household appliance brands are like this (such as Cankun, Delong, Electrolux, etc.). After all, these brands are not professional coffee makers. Another thing to consider is a good heat conduction material, a good machine has a better circuit and pipeline design, using copper or stainless steel as the main material of the coffee machine, they have good thermal conductivity (to ensure uniform and stable temperature). Otherwise, it is still more than 90 degrees from the boiler to 70 or 80 degrees out of the coffee machine, which will be more obvious in the low temperature environment since we can't afford to play with Tuhao coffee machines. That's a return to the traditional espresso machine, to the half-century-old espresso's golden rule of "extracting 1 ounce (about 30ml) of espresso (espresso) in 25-30 seconds at 9bar pressure at a temperature of 90-92 degrees Celsius."

Although this golden rule is still controversial in professional coffee forums in recent years, 9bar pressure is basically not controversial, so a bunch of coffee machines boasting 15bar or higher actually refers to the most high pressure of the coffee machine, which is of little significance, and is generally used to fool newcomers. Stable pressure and stable temperature are the criteria for measuring Italian coffee machines.

Now that you know the two most important factors of espresso (espresso), you can choose the espresso machine, all traditional espresso machines are designed around these two factors.

In the Italian coffee machine, the pressure value is mainly affected by the water pump, which is divided into the vibration pump and the rotary pump. The pressure curve of the vibration pump fluctuates, while the pressure curve of the rotary pump tends to be a straight line. Unfortunately, the machine of the rotary pump is not less than 8000 at present.