Cleaning and maintaining your equipment

Coffee equipment accumulates two things: oils, which go rancid, and mineral scale, which impairs function.

Both degrade the cup, and both are entirely preventable.

Why rancid oils matter

Coffee oils oxidise over days and weeks, developing a stale, greasy, faintly bitter character.

Every surface that contacts coffee accumulates them: grinder burrs, brewer, filter baskets, portafilters, group heads, carafes, and metal filters.

A brewer that has not been cleaned in months contributes that character to every cup, and no amount of fresh coffee overcomes it.

The characteristic symptom is coffee that tastes stale and slightly rancid regardless of beans, technique or freshness.

The grinder

The most neglected item.

Regularly, perhaps monthly, brush out the burr chamber and the exit chute with a stiff brush.

Every few months, disassemble as far as the design allows and clean the burrs properly.

Do not wash burrs in water unless the manufacturer says to — most are steel and will rust. Brush and wipe.

Grinder cleaning tablets are made of a food-safe grain-based material that is ground through the machine, absorbing oils and dislodging particles.

Effective, particularly for grinders that are awkward to disassemble. Follow with a small dose of coffee to purge.

Rice is sometimes suggested and is a bad idea. It is harder than the tablets and can damage burrs or motors.

Brewers

Rinse thoroughly after every use. Hot water and a brush.

Deep clean periodically with a coffee-specific cleaning powder, which is alkaline and dissolves coffee oils in a way detergent does not.

Soak the brewer, carafe and any metal filters in a solution, then rinse very thoroughly.

French press. Disassemble the plunger — the filter unscrews into several parts — and clean each. This is the most commonly skipped step in coffee maintenance, and the mesh accumulates oil rapidly.

Aeropress. Clean the rubber seal, which holds oils. Store with the plunger only slightly inserted so the seal is not compressed for months.

Drip machines. Run a cleaning solution cycle periodically, and clean the removable basket and carafe.

Also clean the water reservoir, which grows biofilm if water sits in it.

Espresso machines

The most demanding, and the routine matters.

Daily. Wipe the group head gasket and screen, flush the group, clean the portafilter and baskets, wipe and purge the steam wand immediately after every use.

Weekly. Backflush with a blind basket and espresso machine cleaning powder, on machines with three-way valves.

Soak the portafilter and baskets in cleaning solution — not the plastic handle if it is not rated for it.

Clean the shower screen, which unscrews on most machines and accumulates a remarkable quantity of grounds and oil.

Periodically. Replace the group gasket, which hardens and leaks. Typically annually with regular use.

Soak the steam wand tip to clear milk residue.

Descaling

A separate problem from oils.

Calcium and magnesium precipitate out of water when heated, forming scale on heating elements and inside pipes.

Scale insulates heating elements, which lowers brew temperature — frequently the real cause of a machine that has gradually started producing sour coffee.

It also blocks pipes and can damage components.

Frequency depends entirely on water hardness. With hard water, every couple of months. With soft or treated water, much less often.

Use a proper descaling solution or citric acid, following the manufacturer's instructions.

Vinegar works chemically and is harsh on seals and leaves a persistent smell. Avoid it in machines with rubber components.

Rinse extremely thoroughly afterward. Descaling residue tastes appalling.

Note that some machines should not be descaled with certain solutions, particularly those with aluminium components. Check the manual.

The better answer is prevention. Using softened or appropriately treated water dramatically reduces scale formation and is easier than descaling.

Kettles

Descale regularly. Scale in a kettle affects heating and flakes into the water.

Gooseneck kettles with narrow spouts benefit from a bottle brush.

Milk equipment

Milk residue is a hygiene issue as well as a flavour one.

Purge and wipe the steam wand immediately after every use, before residue dries.

Soak wands and pitchers periodically in a milk cleaning solution.

Automatic milk systems require their own cleaning cycles, run as specified.

The schedule worth keeping

Daily: rinse everything that touched coffee, wipe the steam wand.

Weekly: brush the grinder, backflush the espresso machine, wash the French press filter assembly.

Monthly: deep clean brewers and baskets with coffee cleaner.

Quarterly: disassemble and clean the grinder, replace filters, check gaskets.

As needed by water hardness: descale.

Fifteen minutes a week, and it eliminates an entire category of problems people otherwise chase through recipes.