How to Clean a Greasy Kitchen Extractor Filter Properly

Why Your Extractor Filter Needs More Than a Quick Wipe

If you cook regularly, your extractor filter is quietly doing one of the hardest jobs in the kitchen. It traps cooking fat, steam and airborne particles before they settle on your walls, cupboards and lungs. Over a few weeks, that trapped grease builds into a sticky, amber-coloured layer that reduces airflow, makes the motor work harder, and leaves your kitchen smelling faintly of last night's chips.

For most UK households, metal mesh filters need a proper clean once a month — and every fortnight if you fry, roast or use a wok often. Carbon filters, which are usually found in recirculating hoods, cannot be washed at all. They should be swapped every three to six months depending on use. Check which type you have before you start soaking anything.

What You'll Need (Mostly Cupboard Staples)

You do not need specialist degreasers. The alkaline and acidic staples already in your cupboard do the heavy lifting, and they cost pennies.

• Washing soda crystals — the star of the show, brilliant at cutting through fat
• Bicarbonate of soda — for paste on baked-on patches
• White vinegar or lemon juice — for the final rinse and to lift lingering smells
• Washing-up liquid — a good squeeze helps the solution cling
• A kettle of just-boiled water
• A roasting tin or washing-up bowl big enough to lay the filter flat
• Rubber gloves, an old toothbrush and a non-scratch sponge

Work near an open window or with the extractor running on low. Washing soda is gentle on skin in small doses but will dry your hands out, so gloves are worth it.

The Soak-and-Lift Method

This is the method I recommend to anyone who has ever scrubbed a filter for twenty minutes and got nowhere.

• Remove the filter. Most metal mesh panels unclip, or have a small tab you press. Some sit behind a metal grille held by two screws.
• Scrape off the worst. Take it over to the bin and use an old spatula or the edge of a spoon to lift visible fat into the bin — never down the sink, where it will set like concrete in your pipes.
• Build your soak. Lay the filter flat in the tin. Sprinkle over two to three tablespoons of washing soda, add a generous squirt of washing-up liquid, then pour on enough just-boiled water to cover it.
• Leave it for 15 to 30 minutes. You will see the water turn cloudy and brownish as the grease lifts. Resist the urge to poke at it too early.
• Brush gently. Use the toothbrush to work along the mesh in the direction of the channels, then flip the filter and repeat. A sponge handles the frame.
• Rinse in hot water. Hold it up to the light. If you can see through the mesh clearly, it is clean. If it still feels tacky, repeat the soak once more.

When the Grease Has Baked Itself On

Older filters, or ones that have not been cleaned in a year, develop a hard, varnish-like coating that a simple soak will not shift. In that case, make a thick paste from bicarbonate of soda and a little water, spread it over the affected areas, and leave it for ten minutes before brushing. The gentle abrasive action does the work.

Another favourite trick is to lay the filter in the sink and pour a kettle of boiling water straight over it, letting the steam and heat soften the fat before you begin. If there is a persistent smell, finish with a rinse of one part white vinegar to four parts warm water.

Dishwasher, Aluminium and Other Caveats

Many metal filters are dishwasher safe, and if yours is, pop it on the top rack on a hot cycle with no other greasy dishes. Do bear in mind that dishwashers can dull aluminium over time, leaving filters looking grey or chalky even when they are perfectly clean — that is cosmetic, not a problem.

What you should never do is put a carbon filter in water. Soaking it destroys its absorbent structure and it will no longer remove odours. These are a replace-not-repair item.

Also, avoid caustic oven cleaner on extractor filters. It can pit the metal and damage the finish, and the fumes are unpleasant in a small kitchen.

Refitting and Keeping It Cleaner for Longer

Let the filter dry completely before refitting — moisture in the housing encourages mould and leaves a musty smell every time you switch the hood on. A quick blast with a clean tea towel and ten minutes on the draining board usually does it.

Once it is back in, adopt two small habits. First, wipe the underside of the hood and the filter housing with a hot, soapy cloth each week while you are already cleaning the hob, so grease never gets a chance to set. Second, run the extractor for five minutes after you finish cooking, not just during — that clears the last of the steam and fat particles before they settle. Ten minutes a month, a kettle of hot water and a scoop of washing soda is really all it takes to keep your kitchen smelling fresh and your hood working as it should.