The espresso machine seems like a complicated machine, but most of the magic happens inside the group head. What's a group head, you ask? You'll find it on the front of your espresso machine; it's the piece you lock the portafilter into. The group head is, essentially, where water meets coffee and espresso is born.
What Is a Group Head?
The group head is a part of any espresso machine. It is the heart of the machine and responsible for creating a great cup of espresso. Located on the front of the machine, the group head is a metal, permanent attachment that brings water out of the machine and into the filter basket.
A group head is commonly simply called the 'group.' You might also hear it referred to as the 'espresso machine group,' 'brew group,' or 'brew head.'
How an Espresso Machine Works
Whether it is a manual, semi-automatic, or automatic espresso machine, the group head has the same function when pulling a shot of espresso.
- The portafilter is the device that has a handle and holds the basket filled with finely ground coffee. This is locked into the group head.
- When it's time to pull a shot of espresso, the 'group' sends hot, pressurized water from the machine, through a diffusion plate, and into the basket of grounds.
- The pressure forces the water through the coffee and out the bottom nozzles of the portafilter, into the cup or carafe. The result is the concentrated coffee we know as espresso.
Like portafilters and baskets, the size of the group head varies with the type of shot you are pulling.
For proper function, follow these tips:
- Before pulling a shot, several ounces of water (or practice shots) should be run through the machine to, among other things, stabilize the temperature of the group head.
- To retain heat inside the group, reattach the portafilter (with a clean basket) in between shots.
Group Head Maintenance Tips
A well-functioning group head is critical to pulling great shots of espresso. That means that it needs to be properly maintained and cleaned to continue working correctly.
Inside the group head are two pieces that can (and should) be replaced on a regular basis:
- Group Gasket–A large rubber O-ring that fits inside a groove in the group head. This ensures a tight fit between the portafilter and the group head. If your portafilter is leaking water, it's likely time for a new gasket.
- Group Screen–Also known as a dispenser or shower screen, this screen is found inside the group head through which the hot water flows.
In professional coffeehouses that pull many shots of espresso a day, it's recommended that the gasket, screen, and portafilter basket be replaced every three months. With in-home espresso machines with less use, check the condition of the group gasket regularly and replace all three when you notice it wearing thin.
Finding replacement parts for commercial as well as many manual and semi-automatic home espresso machines is easy, and a few stores specialize in espresso machine parts. Automatic espresso machines intended for home use are more difficult but parts may be found through the manufacturer.
In most machines, the group head is designed for easy cleaning and this should be done regularly.
- Follow the cleaning directions for your particular espresso machine and maintain the regular schedule recommended. Many will advise something like 'every 200 shots,' and you can estimate that based on your regular use.
- Do not use scouring pads on any metal parts, as this can damage the surface and negatively impact the machine's performance.
- It's best to use an espresso machine detergent whenever cleaning your machine.