How Espresso Machines Work

Espresso machines are a popular choice among coffee lovers due to their ability to produce rich, flavorful coffee in less than a minute. But how exactly do these machines work? Why the fuss around them, and why can we use a regular coffee maker to brew espresso.

In this article we will explain how the espresso machine works, how is such a machine different from other coffee brewing methods, and how this difference affects the final cup.

an espresso machine on the bar
Photo by MART PRODUCTION on Pexels.com

What Is an Espresso Machine?

An espresso machine is a specialized appliance that uses high pressure, hot water, and finely ground beans to produce a rich and flavorful cup of coffee, called espresso.

Typically, espresso machines use a pump that can create 9 bars of pressure for the extraction process. 

What Is an Espresso Maker?

An espresso maker is typically any device that can generate pressure during extraction. The terms machine and maker are interchangeable, though some makers are not machines, such as the AeroPress and the Moka pot.

Types of Espresso Machine

Depending on the amount of technology built into the machine, and the automation level of the extraction process, we can have:

  • Lever operated espresso machines, (many times called manual espresso machines)
  • Semiautomatic espresso machines
  • Automatic espresso machines
  • Super automatic espresso machines

In reality, automatic machines get classified as semiautomatic, and we are talking then about 3 types of espresso machines. 

How Do Espresso Machines Work?

All espresso machines types have the same basic functioning concept: They push pressured hot water through finely ground, packed coffee grounds. 

To a certain extent, steam espresso machines and Moka pots are considered espresso makers, since they use pressure in the brewing process. The AeroPress can be also considered an espresso maker, since it uses pressure as well. 

In fact, the first espresso machines were steam based. However, modern espresso need 8 – 10 bars of pressure to create the rich caffeinated drink that we get in a coffee shop.

how espresso machines work
Schematics that show the internal pieces of an espresso machine and label all components

How Does Pressure Work in an Espresso Machine?

The heart of the espresso machine is the pressure generating system. For most equipment that is the pump, but manual, lever operated machines use a piston to create pressure in the coffee puck. 

As we mentioned before, the pressure can also be generated by steam, though there are very few steam based espresso makers that can generate enough pressure to qualify as modern espresso making devices.

The pressure is the most unique feature of an espresso machine, and the brewing method. Pressure brewing works by creating more kinetic energy in the coffee grounds, and speeds up the dissolution of the soluble solids from the beans. If you want an analogy, is like the pressure washer versus the regular tap hose. But it is more than that because the pressure is what creates crema. More on how pressure and temperature affect solubility here.

How Does Hot Water Work During Espresso Making?

The other important part of an espresso machine is the heating element. The heating element heats up the brewing water. Then only when the water is at the right temperature, the barista pushes a button and starts the brewing process.

The hot water is then pushed by the pump through the grounds, and will start the dissolution of the coffee solubles. Hot water also increases the kinetic energy of the molecules, speeding up the dissolution.

The water temperature is similar to other brewing methods. But because of the addition of pressure the brewing process is faster. Compare 5 minutes brewing time for drip coffee makers to 30 seconds for espresso. The faster extraction time results in a selective dissolution. In other words we don’t extract the bitter stuff from the beans. We talk about this more in our extraction article. 

How Do Espresso Machines Heat the Water

Most machines will take the cold water from the water line supply, or from the built in water tank, and heat it up. Some manual devices require a separate water heating method. But these are purposely built completely manual, so they can be used in the absence of electricity. 

The water is heated using various methods, the most common are: boiler, thermoblock, and thermocoil. Al these methods are powered by an electric element, and have a way to control the temperature such as a thermostat, pressurestat, or PID.

So the water is heated by an electric element, but we need a lot of water if we want to pull more than one shot of espresso. This is where the boiler, (thermocoil), comes in handy. The boiler can hold 8 ounces or more of hot water, that can be used for pulling shots, or steaming milk. 

A boiler works by holding a large amount of hot water, that can be used for subsequent shots. You heat the boiler up, and you have a finite amount of water. 

A thermocoil delivers the water on demand. As water passes through the thermocoil, it reaches the correct temperature, and is pushed further by the pump.  

How Does The Portafilter Work?

After water was heated and pushed through the pipes inside the machine, it reaches the portafilter. Actually, it reaches the brew head. The brew head is a set of a few pieces where the actual espresso brewing happens. 

The portafilter gets locked very tightly to the exit of the machine, and there is a gasket that ensures pressure does not escape.

The water gets pushed through a shower screen into the portafilter, through the coffee puck. The portafilter is a big handle with a holder that takes a metallic filter basket. The filter basket retains the spent coffee grounds, and lets the brewed drink flow into the cup. 

Ideally, we want to create 9 bars of pressure in the portafilter. This was observed that yielded the espresso shots with the best aromas and flavors. So in order to create this pressure, we take in consideration the basket holes, the amount of ground coffee, and the grind size. 

If we create too much resistance in the puck, water will pass too slow, and the shot will over-extract. If there is not enough resistance in the puck, water will pass too fast and the shot will be under-extracted. This fine balance is sometimes missed by beginner home-baristas, and companies have created pressurized portafilters, which create pressure regardless of the grind size and the coffee does. 

Do You Need a Filter for Espresso?

No, a cup of espresso is ready to be consumed as soon as it’s ready. The filter basked will retain the spend grounds, and allow only the brewed beverage into the cup.

The filter basket is very similar to the Moka pot filter, or the French press screen. It allows all of the coffee oils to pass through and a decent amount of micro particles, which baristas call fines. 

Can Espresso Machines Make Regular Coffee?

You can make a longer drink, that is closer to the beverage you get from a regular coffee maker, but it will still have the flavor of an espresso drink. 

Is Espresso Made with Steam or Water?

Steam espresso makers will push steam directly on the coffee grounds, so they use steam. However, modern espresso is brewed with hot water, as steam is too hot and over extracts coffee. 

Can You Make Espresso with a Drip Coffee Machine?

No, you cannot make an espresso drink with your regular coffee maker. The flavor and the consistency will just not be the same. 

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