Coffee brewing method: the principle of siphon pot and matters needing attention in operation

Principle:

When you heat the pot, the temperature of the water in the pot rises. Many people think that the principle after that is that the kettle boils and the steam pushes the hot water over the kettle. The principle is correct, but the obsessive-compulsive disorder of physics as a university should be explained here:

To be exact, the principle is that the lower kettle produces a large amount of water vapor in the process of rising temperature. originally, there is air above the lower kettle, coupled with water vapor, so that the air pressure above the surface of the lower kettle is higher than the external atmospheric pressure. this requires balancing the air pressure by connecting the lower kettle to the outside world, that is, what we call "the water in the lower kettle has been pressed up"-- we can't say scientifically. It is the pressure in the kettle = the external atmospheric pressure + the water pressure produced by the water being pressed up, thus forming a pressure balance system.

The mistakes we usually make here are:

1. Think that the next kettle is boiling, in fact, you can find: under normal pressure, the boiling point of water is 100 degrees Celsius, then, if the water really boils, the temperature of the water on the upper pot is theoretically 100 degrees Celsius, considering the heat dissipation, it will not be lower than 90 degrees Celsius, for coffee extraction, this temperature is much higher than that of the hand, and the powder of the siphon pot is finer than that of the hand, and the contact area between coffee powder and hot water is larger than that of the hand-you know. So the water in the pot should not be boiling. Since we don't have a siphon pot, it's like asking everyone who uses siphon to measure the temperature of the upper pot. If it's not very high, it means our theory should be correct.

two。 Think that the pot high pressure, simply said that high pressure is right, but said that high pressure boiling is absolutely wrong! If you want to get to junior high school, it is estimated that the physics teacher will beat you half to death-- because-- the higher the pressure, the higher the boiling point! 100 degrees is not high enough? More than a hundred degrees of extracted coffee? Are you sure it's extraction instead of baking (just kidding. The baking temperature is much higher. The example in junior high school textbooks is that the temperature of boiled water on the Qinghai-Tibet Plateau is less than 100 degrees. The reason is that the pressure on the Qinghai-Tibet Plateau is low and the boiling point is low.

With regard to the boiling point, there is a common sense mistake that pressure determines the boiling point. In fact, the boiling point is defined as "the temperature at which the saturated vapor pressure of the liquid is equal to the external pressure." No one decides who says. I once saw a video made by hand, in order to remove the bubbles inside the mold, the mold needs to be put into a sealed low-pressure box to reduce the pressure, so that the bubbles in the cast model will overflow. In the process of decompression, you can see the sap liquid boiling at room temperature, yes! That's boiling! Decompression at room temperature can be boiling, and liquid oxygen boiling point is below zero at atmospheric pressure, it can be understood that before the temperature reaches-182 degrees Celsius, the oxygen is liquid, when the oxygen is "boiled", when we see the oxygen, people have already boiled.

It should be noted that in the process of rising, the lower kettle also has the role of thermal expansion of the lower kettle air, and the lower kettle air has a weak thermal expansion effect in the early stage of the upper water, because although the heat source is heating the lower kettle, because the thermal conductivity of the glass is poor, so if the heat source is still some distance from the lower kettle air, the glass temperature in contact with the air is not high enough to heat the air. In addition, the water in the kettle also absorbs a lot of heat (the specific heat of water is very high, much higher than that of air, and absorbs a lot of heat!)

But when the heat source comes into contact with the next pot of air through the glass, the air will expand strongly. The effect of air thermal expansion is very obvious, and the speed is also very fast. At this time, the remaining water is immediately topped up by the madly expanding air before it can absorb heat.

-until the pressure of the next pot = external atmospheric pressure + the water pressure of the upper pot due to height.

Note:

1 dry the next bottle, no water droplets

2 when pulling out the upper seat, tilt to the right and pull it straight up. Do not break it.

3 the spring under the middle filter should be tightened, the hook should be hooked, and pulled to the center

4 when plugging into the seat, plug it down tightly.

5 pay attention to water quality: pure water, purified water, magnetized water, distilled water, do not use mineral water

The temperature is between 80 and 90 degrees Celsius.

7 punch time: all 50: 60 seconds (do not exceed the time too long)

Coffee beans should be fresh, do not get damp or keep for too long

9 it is best to brew coffee freshly

10 pay attention to the direction of the wind when brewing coffee, do not blow the source of fire directly

11 pay attention to the size of fire sources: strong fire, large fire, medium fire, small fire, small fire

12 the boiled coffee powder is slapped loosely, poured out and then rinsed with clean water on the bottle

13 the number of grinding bean segments is about 2, 5, 3 and 5, the basic principles are: acid bean rough grinding, bitter bean fine grinding, high new section and low old section.

14 the coffee cup should be warmed first.

15 the filter should be soaked in clean water or refrigerated to prolong the service life of the filter cloth

16 when pulling out the upper seat, focus on the left hand to hold on to the handle of the lower seat

17 the water in the lower seat had better use hot boiled water, which can save boiling time.

18 the poking method should be correct, do not use the stirring method

19 the remaining water in the lower seat had better be poured out, and when the coffee is almost finished, the remaining foam will be separated.

20 when the stick is moved, just insert 2 + 3 places, do not scrape to the bottom of the filter.

21 the stick should not touch other moisture in the middle of boiling and then take it back and pull it.

22 Coffee powder and water quantity should be correct

When cooking, cover the upper seat with your hand, smell it with your nose, or fan it with your hand, and then smell it with your nose

24 wipe the lower seat with a wet cloth, wipe the bottom first, and then wipe the left and right sides

25 the formula of coffee beans should be correct.

26 be sure to wait for the water to boil before you insert it into the upper seat.

Source: network