Most of us either buy coffee from Starbucks or have a coffee maker at home. But do you ever stop and wonder how these coffee makers actually work? Well, I have, and so I did my research. Although there are several different types of coffee makers, most of them use the same or similar principle to extract the coffee flavor from grounded coffee beans that are used while brewing coffee.
Most coffee makers either use heat or pressure or both to extract coffee flavours from the coffee beans. This is done by passing hot or pressurized water through grounded coffee beans. While the water passes through the beans it picks up the coffee oil and other compounds within the coffee, this is then usually collected in a separate area and is now coffee ready for your consumption.
Different coffee makers work in different ways, so I have written below about some of the most common coffee makers and how they work in more detail.
Drip Coffee Maker
This is most likely the most common type of coffee maker in many households. This is because it’s affordable and easy to maintain and not to mention it makes great coffee!
You first have to fill the reservoir with clean cold water.
The water from the reservoir flows down a tube and this tube passes over a hot plate that heats up the water which causes the water to bubble. These bubbles then push small quantities of water with them up the tube causing them to drop on the filter paper with coffee in it. As these warm drops pass through the grounded coffee they pick up coffee oil and pass through the filter paper leaving the coffee behind and collecting in the pot below. The hot plate has a heat sensor to prevent it from overheating and is powered by electricity. There is also a one-way valve that prevents water and the bubbles from entering back into the freshwater reservoir.
Espresso Coffee Maker
Espresso is an Italian word that literally translates to “pressed coffee”. As the name suggests this machine uses pressure to extract flavor from the coffee beans.
To put it simply, water pumps inside the espresso machine pump the water with high pressure which is then heated up and forced through the grounded coffee resulting in maximum extraction of the flavors from the grounded coffee.
Since high pressure is used the coffee beans can be ground even more finely when compared to other methods as the water can force its way through and thus this gives the coffee beans more surface area from which the water can pick up more coffee oil and other compounds within the coffee. This results in a stronger and darker coffee as the flavor is more efficiently picked up.
Moka Pot
In my personal opinion, Moka pots are the best way to make coffee at home. These are somewhat like mini espresso machines when you understand how they work. Moka pots also use pressure as the main way to extract the coffee flavors.
Water is filled in the water tank, this water is then heated with an external source like your cooking stove. This causes the water to boil and pressurize, due to this pressure the water forces its way through the filter basket containing the grounded coffee. As it passes through it collects the coffee oils and other compounds and then still having pressure forces its way to the upper tank where it gets collected.
The water can either pass through the grounded coffee either as hot liquid water or as steam. This depends on different factors such as the temperature and pressure that a particular Moka pot can withstand.
Due to its size and design, the maximum pressure is around 1.5 bars to 2 bars of pressure at 100°C (water & steam) whereas espresso machines usually can reach 9 bars of pressure at around 95°C. The difference in pressure and temperature results in a difference in the final brewed coffee.
This is the main difference between a Moka pot and an espresso machine. In my humble opinion, Moka pots are well worth it as they are easy to use and maintain and a fraction of the price of an espresso machine and provide almost the same experience at least to most average people who don’t go nitpicking.
Moka pots were invented by Alfonso Bialetti in 1933 and had revolutionized the coffee culture of Italy and then the whole world.
French Press
A french press is simple to use and easy to understand. Yet it is one of my least favorites. More on that later.
It works simply by adding grounded coffee beans into the carafe (beaker) and then filling it with boiling hot water, then stirring for a few seconds. This causes the hot water to soak up the coffee oils and other compounds from the coffee beans. Then the lid is placed on top, this prevents the heat from escaping and lets the coffee brew. Then the plunger is pressed down slowly and collects the coffee beans along the way.
The biggest drawback of French Press is that the mesh of the plunger cannot catch the fine coffee particles and so may end up in your coffee drink. Also, you would not want to use the bottom portion of the coffee as it may have more coarse coffee. This is because the french press lacks any kind of paper mesh-like other coffee makers of a similar type.
Electric and Stove Top Percolators
These were widely popular before the 1970s, after which the drip coffee makers gained popularity.
Percolators coffee makers mainly use heat to brew the coffee. Water is heated and made into steam which then rises, gets soaked in the grounded coffee beans, and then cools and drips back down. The cycle is repeated again and again by supplying heat until the desired concentration is reached.
The electric percolators simply have a heating element under them powered by electricity and so are generally used at home. The stovetop gets its heat from a stove top’, these are also used at home but also while camping as they can simply be placed over the campfire to make some coffee.
Cold Brew Coffee Makers
As the name suggests these coffee makers use cold water, so there is no pressure or heat added resulting in a coffee that is less acidic but depending on the brewing time just as strong and tasty!
This is more of a ‘method’ so does not require any special utensils or equipment like other coffee makers.
To cold brew coffee, simply add some grounded coffee to a jar or container and add some room temperature water. Stir well and then keep it in the fridge and leave it for a couple of hours. Most people keep it for 16 to 20 hours but you can keep it much longer. Then just slowly pour the coffee into another jar while leaving the course residue behind.
The longer you leave it, the stronger it gets.
Many people like to use the french press for this as it has a mesh in it so no need of pouring the brew into another jar, just press down the plunger slowly. But make sure to do it after brewing i.e. after 16 to 20 hours. You can also use a mason jar or any other jar, just make sure you cover it with a cheesecloth tightly.
Although today you get dedicated cold brew equipment, which I think is unnecessary at best you can achieve the same results with a mason jar.
AeroPress
The Aeropress method was invented in 2005 by Alan Adler and so is a relatively new way of brewing.
The Aeropress has 4 main sections to it, the chamber, plunger, filter, and cup. The cup is used to collect the brew.
The chamber is placed over the cup with the filter attached to its bottom end. Grounded coffee is added to this followed by hot water (about 94°C) followed by a quick stir and allowed to sit for 1.5 minutes. The plunger is placed on top and is slowly pressed down. This forces the water through the coffee beans collecting their flavors and passes through the filter to collect in the cup underneath.
The Aeropress is loved by many because of its portability and durability. Many use it while on an adventure like camping or mountain climbing or while just traveling with family. This has only bolstered the reputation of the Aeropress even more.
Siphon Coffee Maker
This is one of the most advanced and sophisticated coffee makers out there, and to be honest quite flashy too.
To understand how this coffee maker works we need to know a basic law of physics i.e. hot things expand and cold this contact. When hot things expand in a fixed space, the pressure increases (like in the water Moka pot which turns into steam). And the opposite is also true, when cold things contract in a fixed space the pressure decreases.
The siphon coffee maker has 4 main parts,
- The upper pot, usually a beaker with a long tube-like structure as the opening
- The lower pot, usually something like a round bottom flask
- Siphon ring with filter (also spelled as siphon)
- Burner (heat source)
It also has a stand to hold the upper and lower pot.
First, the lower pot is placed on the stand and filled with water, then the burner is lit and placed under it. The upper pot with the siphon ring and filer already placed in it is placed on top of the lower pot. The burner causes the water to boil and increases the pressure. This increased pressure allows the water to force its way to the upper pot. Once most of the water is in the upper pot, grounded coffee is added and stirred quickly which brews the coffee.
Then the burner is put off causing the lower pot to cool down. As the pot cools down the pressure decreases and creates a vacuum. This sucks the water back down through the filter not allowing the grounded coffee through.
The end product is brewed coffee in the lower pot. This uses the change in pressure due to temperature to brew and filter the coffee.