Group head brushes

Mechanically lifts spent grounds and softened oil off the gasket groove, the shower screen face and the seating rim — the outside of the group, which pressure never touches.

Backflushing cleans the inside of the group; the brush cleans the outside of it. The gasket groove, the underside of the shower screen and the rim the portafilter seats against are where grounds pack in and where oil polymerises into a varnish once heat has worked on it. The mechanism is abrasion at a deliberately chosen hardness: nylon filaments are hard enough to lift baked coffee off stainless and brass, and soft enough not to score the sealing face or open out the screen's perforations. Geometry does as much work as the filament — the bent neck exists so the working surface is above and behind the bristle tip, which is the only way to reach up into a hot group without putting a hand into it. That matters because the deposit is soft when the machine is hot and glassy when it is cold, so the brush has to be usable at the moment the deposit will actually come away. Some patterns add a scraper edge for the gasket groove, where packed grounds behave less like a soil and more like a solid.

• Buy the brush that matches the group geometry you actually have, and test it against a hot group before committing to a case. Recessed and saucer-shaped groups want different neck angles, and a brush that cannot reach the gasket will not be picked up a second time.
• Give every group its own brush and keep a spare within reach of the machine. A brush that lives in a drawer at the other end of the bar produces a close in which the groups are 'brushed' by wiping the rim.
• Confirm heat rating with the supplier rather than assuming it. The failure being designed out is a bristle in a served drink, and the cost of that event has nothing to do with the price of the brush.
• Prefer a detachable head where spend is controlled by a manager who never sees the tool, and prefer whatever the team will actually replace where it is not. Buy for the behaviour you have, not the one on the org chart.
• Keep the group brush and the grinder brush visibly different — different colour, different shape, stored apart. A brush that migrates between coffee oil and burr-chamber dust moves oil into the grinder and metal fines into the group, and neither shows up until the coffee tastes wrong.
• Never buy a brass- or steel-bristled brush for a group head. It removes the deposit and the sealing surface together, and the leak arrives months later with no obvious cause.
• Size the handle for a gloved hand working fast on a hot machine, sometimes by someone whose shift has already ended. A handle that needs a precision grip loses to one that does not.
• Replace by inspection, not by calendar. A splayed, matted or discoloured brush is retired that day. Put the check on the same walk as the gasket inspection so it belongs to somebody rather than to everybody.
• Remember what this tool is: not a chemical, so it lives at the machine — but it touches a surface every subsequent drink passes over, so it is washed and sanitised with the rest of the bar's food-contact tools rather than rinsed under a tap.