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Clean brewing equipment is an absolute necessity for the best coffee flavour, so it's surprising how often I see various brewers layered with old coffee gunk. The problem is simple, coffee oils tend to stick to most surfaces, and when they oxidize they form a tarry coating.

Oxidized coffee oils also have a horrible rancid taste, which easily contaminates a fresh brew. Prime culprits are often the filter screens of plungers and moka pots and the filter holders in drip brewers. All of these can usually be easily removed for a good scrub with hot water and detergent, followed by a thorough rinse.

When it comes to espresso machines, though, the cleaning requirements get a little bit more complex. First, the most used bits, the portafilter, filter baskets, shower screen and gasket should be cleaned every day. You can get special espresso machine cleaners which are mostly trisodium phosphate, but a good wash in hot water and detergent will do for the portafilter and baskets. The showerscreen can be wiped with a soapy sponge, as can the rubber gasket. The gasket can also be cleaned of grounds with a brush, a bent "kiddy" toothbrush works well.

Remember to rinse everything clean; you don't want detergent flavoured coffee!

About once a month the showerscreen can be removed for cleaning. It's important to use the correct sized screwdriver so you don't strip the screw; there are pictures with this month's internet newsletter showing the procedure. Use a scotchbrite with detergent to clean the group, and if the screen is really dirty and the holes are blocked, a wire brush can work wonders. When you replace the showerscreen, the screw should only be "finger tight". In between the daily and monthly cleaning machines with solenoids can be "backflushed" about once a week to clean out the showerscreen and water path to the solenoid.

Lelit group and showerscreen

Removed and cleaned

Silvia group and showerscreen

Cleaned (note water distributor washer)

IMPORTANT NOTE! None of the domestic espresso machine manufacturers recommend backflushing, and any damage that occurs while you're doing it will not be covered by warranty!

That said, there is an excellent "how-to" tutorial on Randy Glass' website at http://www.espressomyespresso.com that takes you through the necessary steps. You do need accessories like blind filters and espresso machine detergent.

Silvia Portafilter with blind filter basket

Lelit Portafilter with modified single filter

Unfortunately no equivalent basket exists for the Lelit machines, so again there are photos on the website showing how to make do. I use a circle of self adhesive foil tape in the bottom of the single filter basket, as you can see.

Finally, machines should be descaled about every 6 months or so. You can use expensive commercial descaler or plain citric acid from the supermarket. First, remove the showerscreen (and the water spreader washer on the Silvia).

$1.50 for 75g...cheap!

Simply dissolve 10g of citric acid in a cup of hot water, then add cold water to make the quantity up to a litre. Replace any water in the tank with the citric acid solution, then run 300ml (one and a half cups) of water through the group, then turn off the machine. Wait 20 minutes then turn on again and run another 300ml out, this time through the steam wand, then turn the machine off. Repeat once more, then empty any remaining solution from the tank, flush with clean water, refill and run about a litre of clean water through the machine, alternating between the group and the steam wand. Replace the showerscreen (and washer spreader) and you're ready to brew again.