Your Espresso Machine: The Brew Group, and How to Clean It

This Brew Group is Where the Espresso is Extracted

A closeup photo of the brew group and its diagram is shown below. This is the basic brew group used in all commercial espresso machines and the high-end home machines today. The brew group of the espresso machine comprises a tower through which hot water flows constantly, and the round bell-shaped portion into which the barista locks the portafilter. We'll describe the operation of the brew group shortly.

The E61 Group Has Become Standard on Espresso Machines

In the figure below, the portafilter is shown from a top view, and (a different one) from the sideview. Note that the filterbasket has not yet been placed into the portafilter. Two filter baskets are shown on the right side of this figure. The top basket is for a double shot of espresso (note the filter grid in the bottom of the basket), and the bottom one is a "blind filter" (having no holes) used for cleaning the machine with a backflush operation (to be explained shortly).

The Portafilter with a Filter Basket and a Blind Filter for Cleaning

In the figure below we show the internals of the E61 brew group. On the top left is the water inlet port, and under it is the water outlet port. As we've already said, hot water flows constantly through the brew group of the espresso machine to keep it hot. With the cam in the position shown, water does not flow into the brewing channel, but it flows everywhere else throughout the head to keep it hot.

Inside the E61 Grouphead: How the Water Flows for Heating and Extraction

When a shot is pulled, the water inlet cam rotates clockwise to open the preinfusion chamber, which injects a small amount of hot water into the group through the infusion channel. This gives the espresso in the portafilter an initial (lower temperature) soaking to prepare for extraction. As the water inlet cam continues to rotate, the brewer valve opens, and the "gicleur" (this is French for "nozzle") is opened in the filter chamber. There is a filter screen in this chamber to prevent particles from entering and clogging the infusion channels - which are quite small. The infusion channels take the hot water through to the filter basket (not shown) through the dispersion screw (or through a more exotic dispersion plate, as we'll see).

We've mentioned "temperature" a number of times, and have said that the key innovation of the E61 brew group was the continuous flow of water to keep the channels hot. In the figure below, we show the thermal profile of an E61 group when the water source is calibrated to 197.5 degrees. Note that the region with the large active water channels (input and ouput flow) is held at 197.5 degrees (Red) by thermal regulation. Since the group itself is "in the room" (at room temperature), the group cools as we look at the head further from the water input. The very edge of the group has cooled to about 190 degrees (i.e., a loss of 7 degrees).

Thermal Profile of an E61 Group with a 197.5 Degree Brew Temperature

The next figure shows a closeup of the brew group on the espresso machine. Note that it is only a few inches above the drip tray (left photo), and if you look up inside the brew group from below (right photo), you can see the shower screen held in by a screw. To unscrew this for cleaning, you will need a short screwdriver (center) which we can provide if you don't have one. If it does not unscrew easily, DON'T force it. We'll explain in a bit.

In this photo, looking up into the grouphead you can see the fine-mesh screen (for uniform dispersion of water), and the coarser grid behind it - to disperse the water across the screen. The grid and screen are joined together as a single unit, and should be replaced periodically. The pocket in between the two will eventually become obstructed with grit from fine coffee particles.

Note also that there is a rubber gasket seated inside the brew group. That is there to form a tight seal when the portafiler is locked into the group head. Notice the large notches in the brass head (top right and bottom left). These are notches for insertion of the portafilter (see the levers projecting from the edges of the portafilter in its top view three photos back). The portafilter is inserted, and twisted by its handle to lock it in. This seal forms a tight joint for espresso extraction.

Looking Up Inside the Group: You'll Need a Short Screwdriver to Remove the Screen

The next photo shows the inside of the group with both the gasket and the screen removed. This is a new grouphead. It's easy to see the notches for locking in the portafilter, and the channel that holds the gasket in this photo. You can also see the brass dispersion plate in the center. This particular plate has a single jet-hole (with a notch) to distribute the hot water across the grid that will be placed over it. Many plates have multiple jet holes.

The Underside of the Brew Group Showing the Hot Water Jet. The Screen and Gasket are Off.

The photos below show three different dispersion plates from different espresso machines. The one on the left has 6 jets. The one on the right has 4. And the one in the middle has 10. In all cases, there is a large hole in the center for attaching the dispersion plate to the grouphead with a screw.

Brass Dispersion Plates from 3 Different Machines. Note the Number of Jets on Each

These jet holes will oxidize, and can also become clogged with coffee and other grit. When you remove the dispersion plate for cleaning, inspect the jet holes. Note that the Pallo brush has a tip on the back of the bristle head that is meant for cleaning out these holes (see below). You should inspect the dispersion plate when cleaning it, and clear the holes if necessary.

Taking the Dispersion Plate Off, and Cleaning the Jets with a Pallo Brush

In the photo below, we show an 8-jet dispersion plate, the group screen that goes over the jets, and the screw that is used to hold the pair up in the brew group. Note that the dispersion plate is brass, and the group screen fixture is stainless steel. For normal cleaning, you should be able to use the cleaning brush with nylon bristles (e.g., the Pallo brush in the previous photo) to clean these. If they need a harder brush to remove particles or corrosion, use the brass brush and the steel brush to do so. Note that steel is harder than brass, so you should NOT use the steel brush on the brass dispersion plate. This is why we offer both brushes.

The Group Screen Goes Over the Dispersion Plate. Both Are Held In With a Screw

The photos below show four different kinds of brushes that you might find useful. The first three are all the same shape, but the bristles are Steel (the hardest), Brass (softer than steel), and Nylon (for general cleaning). You might want a Steel brush for removing difficult residues and/or oxides from Steel pieces of your espresso machine. You should not use the Steel brush on the Brass or plastic parts of your espresso machine. The Brass brush is for difficult cleaning of Brass parts (like the dispersion plate). It should not be used on plastic or ceramics. The Nylon brush is for general cleaning of everything. Note that there is a special Nylon Group brush that has the same type of bristles, but it is shaped so that it is easy to reach up into the group to scrub it. It would be hard to do this with the straight brush.

Four Different Cleaning Brushes. The Nylon Brushes are Used for Routine Cleaning

The next set of photos show the shower screen and the group gasket, and the shower screen within the group gasket. It is this last (the pair together) that fits up into the grouphead. Note that the shower screen fits over the brass dispersion plate, and the group gasket goes around the group screen fixture - up inside the group head. The purpose of the gasket it to make a tight seal when the portafilter is locked in.

The Group Gasket Goes Around the Shower Screen - It Forms a Seal for the Portafilter

The next set of photos shows views up inside the group. The first photo (top left) shows the inside of a new grouphead. The brass dispersion plate is there (in this case, a one-jet plate), but the filter screen is off, and the gasket has not been inserted yet. The next photo (top right) shows a group that has been used for a while. The filter screen is off, but the gasket is in the outside channel. The next photo (bottom left) shows the group with the shower screen in place. This is a group and screen that have been cleaned. And the last photo (bottom right) shows the same group when it's dirty. As you can see it needs cleaning! The screen is covered with a film. Don't let yours get this bad.

Looking Up Inside the Group. How it Looks When Clean and When Dirty

We had mentioned before that sometimes you will find it hard to unscrew the screen. You SHOULD NOT have put this screw in too tightly. If you can't turn it, it's because the screw is stuck to the screen, and the screen is stuck to the grouphead. This is due to grit and oxidation, and it's NORMAL. Do not force the screw. Instead, take a screwdriver (a spoon is shown below), and wedge it under the screen to separate it from the group. A screwdriver is better because you can then bend the screen down and away from the group, thus breaking the seal. (We are going to replace this screen anyway, so it's OK to bend it.) The screw should then be removable easily. See the photo below.

If You Can't Loosen the Screw Easily, First Bend the Screen with a Tool

And finally, an easy way to remove the gasket is with a long screwdriver, or a pick. If the gasket is old and dry, it will likely break apart and crumble. The pick is very good for cleaning out the pieces of it when this happens. The gasket should be kept lubricated with Petrogel. This will keep it from drying out, it will reduce the friction caused by rotating the group on insertion, and it will make a better seal when you're brewing espresso.

Removing the Group Gasket, and Lubricating It with Petrogel

We recommend that you use Petrogel to extend the life of your gaskets, and to create a better seal in your espresso machine. And the pick is a very useful tool to have to get into tight spots in general. You should replace the group gasket every three months to get the best performance from your machine.

You should do a routine cleaning of your machine daily. The standard cleaner for cleaning the brew group is Cafiza powder, as shown in the figure below. To clean the group, put the blind filter into your portafilter handle, measure out a scoop of Cafiza using the measuring spoon on your Pallo brush, put the scoop Cafiza into the blind filter, and lock it into the espresso machine.

Use Cafiza Cleaner in the Blind Filter to Backwash the Group: 5 Cycles X (5 Sec. + 5 Sec.)

Then turn the water to the group ON, as if you were brewing a shot. The blind filter will cause the Cafiza powder to backwash into the E61 group, and will clean out all of the tiny chambers inside. Run the water (that you turned on) for FIVE seconds - NO MORE - then turn the flow off. Wait for 5+ seconds so that the fluid can drain somewhat. Then turn it on for another FIVE seconds. The idea is to repeat this "cycling" (ON for 5, then OFF for 5) about 5 times. This will backwash the grouphead multiple times, and should clean it out nicely.

After 5 "ON-OFF" cycles, unlock the portafilter, and rinse the blind filter to remove any residual Cafiza from it. Then lock the portafilter back into the espresso machine, and do another 5 "ON-OFF" cycles WITHOUT Cafiza. This will wash any residual Cafiza out of the chambers in the brew group.

You should also scrub off the brass dispersion plate and the steel group screen with (hopefully) the nylon brush. If you need to, use the brass brush and/or the steel brush. You can also soak these two plates in a cup of hot water with a little Cafiza added while you clean the rest of the espresso machine, then scrub them off later. Remember that the group screen is two layers joined together, and has a "pocket" inside. That pocket should be clear. Hold the screen up to a light and look through it. If it is full of coffee refuse, you should replace it.

Check the group gasket to make sure that it's still resiliant to the touch. There's no need to pull it out to do this. You can lubricate its surface with a little bit of Petrogel by putting a dab on the tip of your finger, and running it around the top of the gasket where it comes in contact with the portafilter. Replace this gasket roughly every 3 months.

Follow this general routine, and your espresso machine should last a long time, and should brew consistent espresso shots - like it was new! To summarize:

1. Clean the screen and dispersion plate with brushes (and Cafiza) daily;
2. Backflush the group daily - 5X with Cafiza, and 5X with nothing, each time with 5 seconds ON and 5 seconds OFF;
3. Lubricate the group gasket with Petrogel as needed;
4. Replace the gasket about every 3 months.

If you have any questions, let us know. We have all of the cleaning supplies mentioned, and our advice is free. We hope that this article has been helpful to you.

...written by your friends at The Coffee Brewers