Everyone loves a good cup of espresso. But how many of us know how does an Espresso machine work? Espresso machines have gained a lot of popularity these days.
Every coffee shop has one of these machines now. People are buying these machines for their homes too. These machines work as a helping hand for the barista.
It helps the barista by offering 9 bars of water pressure to make espresso and steam froth to the milk. Well, these are the basics. Let’s dig in a bit deeper and learn how espresso machines work.
The Water and Pump
Every espresso starts with the water source. You draw water either from a little reservoir or directly from a plumbed link to the mains. For small volumes, reservoirs work fine but a heavy-use professional machine requires a reliable piped source.
Clean water is essential for a good espresso. Most espresso machines have in-built filters that clear out the extra minerals in the water.
Types of Pumps
Great espresso machines deliver water to the coffee at a predictable pressure and temperature. Normal household water pressure cannot produce enough force to make its way through a condensed coffee puck to make an espresso. This is where the pump comes in to do the job.
Most modern espresso machines use an electric pump to create pressure. You need about 9 bars or 130 PSI of pressure for espresso. 9 bar is 9 times the atmospheric pressure at sea level. Most car tires have 30 to 35 PSI. There are mainly two types of espresso machine pumps.
1. Complex Rotary Pump
You'll probably see Complex rotary pumps in commercial espresso machine more often than machines. Commercial machines need these to supply constant pressure. This kind of pump uses a mechanical disc that is electrically rotating.
2. Vibration Pump
Household machines usually have a vibration pump that pushes and pulls a piston by using an electromagnetic spiral. If you pull the shot, Vibration pumps only generate pressure.
Consistency is important for making coffee. For espresso, your water needs to be at the right temperature to allow proper extraction. You may have already guessed, the boiler does the heating job. Water is moved to the boiler through a one-way valve for heating and storing.
Types of Boilers
There are 3 types of boilers seen in semi-automatic espresso machines.
1. Single Boiler
A single boiler is exactly like the name suggests. Water is stored and heated in a single tank for the brewing of espresso and steaming milk. You cannot simultaneously brew espresso and use the steam wand with a single boiler.
You need different temperatures to perfectly steam milk and brew coffee. Using the same boiler for both means waiting for the water to heat up or cool down after using each function before you can move to the next one.
This is a bit of a pain when you want to get a latte and your espresso starts getting cold waiting for the milk to steam. Single boilers are typically used only in low-end automatic and semi-automatic espresso machines.
2. Heat Exchange
A heat exchange boiler is a large boiler with an isolated section inside it. This isolated section provides cool water that is more suitable for brewing. Water is continuously supplied through the isolated section, into the group head and back into the machine.
You don’t have to wait between using your steam wand espresso shot pulling as you do with a single boiler.
3. Dual Boiler
The Dual boiler named similarly to the single boiler. A dual boiler has 2 boilers for 2 different purposes. One tank is for heating while the other is for steaming. You don’t have to wait for the temperature to change while using a dual boiler.
Dual boilers ensure temperature consistency as each tank can be set at different temperatures. Most modern-day coffee shops use dual boilers. So, a dual boiler is the best choice if you want to steam milk and pull a shot at the same time.
The Group Head and Portafilter
The group head is where the final magic happens. This is the final stop before you have the coffee in your hands. In this part, you mix hot pressurized water with the freshly brewed coffee.
You find the portafilters in the group head. A portafilter is a metal filter basket for holding the ground coffee. You’ll also find a portafilter lock, a pressure switch for regulating boiler pressure, and a channel for allowing water to move from the boiler to the portafilter.
Some people suggest that a bottomless or a naked portafilter is the best way to go. A naked portafilter has an exposed basket which helps a barista to dial in their grinder perfectly.
Types of Group Heads
You will find different types of group heads but all of them are more or less the same. They all consist of the same basic parts with a few different configurations. There are mainly 2 types of group heads.
1. Saturated Group Heads
Saturated group heads can maintain temperature consistency as they are essentially a part of the boiler. The hot water-flood is simply because the brewing water and the group heads have the same temperature. In terms of consistency, they are the best.
2. Semi-saturated Group Heads
A heat exchanger separates semi-saturated group heads from the boiler. Separating the group heads makes them easier to repair. They are also cheap to produce.
However, when it comes to maintaining temperature consistency they fall behind saturated group heads. Both group heads have their pros and cons. Although, most high-end machines include a saturated group head.
Saturated group heads can cost you a bit more money in maintenance. But they are better in terms of maintaining temperature consistency.
So, this was our guide on how does an espresso machine work. If you ever wonder why someone would put so much effort and technology in making a cup of coffee, the answer is simple. A high-quality machine will help you make a perfect cup of coffee with less effort.