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Brewing basic concepts: Working principle of brewers

You might saw or heard that for different brewing methods, there will be different grind size, brew time and techniques to fit with. But in the previous post, we mentioned all different methods are doing the same thing, which is using water as solvent to dissolve solubles in coffee beans. So where are the differences coming from? In this post, we will talk about the working principle of four common brewing equipments.

Dripper (AKA Pour Over)

Most people think this method was invented by Melitta BentzIn in 1908.

In this method, we pour hot water from the top, then water will flow down through the coffee ground due to gravity and dissolve solubles in coffee. At the end, coffee will flow out from filter to our cup.

During the process, there are many factors that we can control, such as pour speed (strong or weak, pause or not) and pour direction (circle or center). And gravity also helps to “pull” solubles from coffee. So variable factors will create different brewing styles, and each style will require different grind size.

French Press

This equipment was originated from France (that’s why it called Frech Press) in 19th century. It contains two parts, a pot (usually made by metal or glass), and a cover with plunger. We just need to put coffee ground in a pot and pour in hot water. Then put on the cover and wait for a certain amount of time. At the end, push down the plunger and pour out the coffee.

In this method, the coffee ground is fully immersed by hot water and water will slowly penetrate into the coffee and dissolve solubles. Different than pour over, gravity won’t involve in brewing process and not much variable factors (some people will stir the coffee ground in the pot to accelerate the dissolve speed though). So, for this method, instead of using fine grind that will cause over extraction easily; we usually use coarse grind size to give us a large time range to make adjustment.

Clever Dripper

From structure point of view, Clever Dripper is still a dripper. The main difference is, there is a control valve on the base of Clever Dripper. In normal situation, the valve is close so the water that poured in will keep staying in the dripper and immerse the coffee ground. In this condition, Clever Dripper is working like a French Press. When the valve open, coffee will flow out from the bottom hole and Clever Dripper work as a normal dripper in this condition. The open and close of this valve gives infinite possibilities to this equipment, letting it switch to gravity or immersion in any time.

The original Clever Dripper is a trapezoid/fan shaped dripper, and the market also has “cone shaped Clever” – Hario Switch and “flat bottom Clever” – December Dripper.

Syphon (AKA vacuum coffee maker)

Invented 19th century’s Germany. This cool equipment will make your coffee brewing looks like a chemical experiment. The equipment has two main parts, upper chamber and lower chamber. We pour water in lower chamber and heat it, once the water boiled, the vapor pressure will force the hot water goes to the upper chamber through the tune. Then we put the coffee ground to the upper chamber, let it fully immersed by hot water. After we finished the extraction, we remove the syphon from heat, then the coffee from upper chamber will flow back to lower chamber due to gravity.

Even though the whole brewing process involve immersion and gravity, the working principle of syphon is closer to French Press since the actual dissolving process is immersion style. However, the variable factors in syphon brew are more than French Press, such as when to put in coffee ground, strong or weak heating during the brew, when to remove the heat and how to stir the coffee ground in upper chamber. So, even with similar working principle, the grind size we use and the brew time in syphon can be totally different than French Press.

Hope this post can helps you understand a bit more on these equipments.

Other articles in this series:

Brewing basic concepts: What are we actually doing in coffee brewing?

Brewing basic concepts: Grinding coffee and grind size