Short answer: that brown layer in your deep fat fryer is not dirt you can scrub off. It is fat that the heat has hardened, and you dissolve it with soda crystals in boiling water.
Short answer
Oil out, water with soda crystals in, twenty minutes on a simmer.
Pour the old oil into a container with a lid first. Then put a shallow layer of water in the pan with two tablespoons of soda crystals and let that simmer gently for twenty minutes. The brown layer lets go and you wipe it away. No scrubbing needed.
Why washing up does not work
You are not dealing with fat, but with something that used to be fat.
Oil that is heated over and over changes its make-up. The molecules link together and form a hard, sticky layer that bonds to the metal. That is called polymerisation, and it is the same reaction that gives a cast iron pan its black layer. The difference is that you want it there and not in your deep fat fryer.
Washing-up liquid is made to lift loose grease. Against a hardened layer it does very little, however long you scrub. That is why scrubbing works so badly here: you are trying to rub away something that is chemically stuck.
Soda crystals do work, and for a different reason. Soda crystals break the fat down into something that does dissolve in water. Saponification is the name for it. So the fat does not come loose, it changes.
How do you clean a deep fat fryer?
Four steps. The pan can be cold, which is actually safer.
- Get the oil out while it is lukewarm. Not piping hot and not stone cold. Lukewarm oil pours most easily and does not splash.
- Wipe out the worst of it with kitchen roll. Anything you remove dry now does not have to go through the water later. That saves you a round.
- Water with two tablespoons of soda crystals, twenty minutes on a gentle simmer. Fill to just above the brown tidemark. Do not let it boil hard, or it will boil over.
- Let it cool, pour it out and wash it up. The layer now lifts off with a wooden spatula or a damp cloth. If anything is left, simply repeat.
If your deep fat fryer has a removable inner pan, you do this with that inner pan. The appliance itself, with the heating element, never goes under water.
Where do you take the old frying oil?
Not down the sink. That is the mistake that ends up costing the most.
Fat sets as soon as it cools. In your drain that means a layer that keeps getting thicker, and that layer then catches everything else coming past. A blockage that builds up this way usually sits further along the pipe rather than in the trap, and at that point it is no longer a matter of unscrewing something.
What does work: pour the cooled oil back into the bottle it came from, or into an empty plastic bottle or a carton with a cap. Take that to a collection point for used cooking oil. You will find them at many supermarkets and at every household recycling centre. Collected frying oil is turned into biofuel, so it gets a second life.
Small amounts soaked into kitchen roll can go in with the general waste. A whole pan cannot.
The film of grease you only notice when you run a hand over it
Deep frying puts fat into the air, and that fat ends up everywhere.
It is the most annoying part of deep frying and hardly anyone talks about it. While you fry, tiny droplets of fat are released that settle on everything within a few metres: the tiles behind your worktop, the cupboard doors, the top of your extractor hood, the highest shelf. You do not see it, you feel it. A sticky film that holds on to dust.
That film is still fresh grease, so there is no need to bring out the heavy artillery. A damp microfibre cloth picks it up without any product at all, and a second dry cloth behind it leaves nothing. Work from top to bottom, otherwise you drag it onto surfaces that were already clean.
Everything for this job is gathered together under kitchen cleaning.
Where a cloth cannot reach
Grout, filters and the underside of the extractor hood.
On a smooth surface a cloth beats almost anything. But grease that has settled into the grout between your tiles, into the metal filter of the extractor hood or into the seam behind your hob does not come out that easily. There it sits in the surface instead of on it.
Heat does help there. Steam at around one hundred degrees softens hardened fat again, after which it lets go and you can simply wipe it away. No degreaser, no gloves, just tap water that has been made hot enough. That is exactly why a steam cleaner works so well in a kitchen: the problem responds to heat, and steam is heat that reaches everywhere.
What you are better off not doing
Most of the damage to a deep fat fryer happens while it is being cleaned.
Wire wool or a scouring pad. They take off the layer and the non-stick coating with it. After that everything sticks even faster.
Oven cleaner. Far too aggressive, and you do not want the residue in something you later heat food in.
Cold water in a hot pan. The difference in temperature can warp the base. A warped base heats unevenly.
The dishwasher, unless the manual says so. The salt and the high temperature leave a non-stick coating dull and porous.
Soda crystals on aluminium. Aluminium discolours and goes dull as a result. If your inner pan is aluminium, use warm water with washing-up liquid and more patience.
How to keep it clean for longer
The layer builds up through heat and time. You can do something about both.
Strain the oil after every session, while it is lukewarm. The crumbs left floating in it burn the next time round and turn into exactly that brown layer. That is the biggest win and it takes two minutes.
Do not fry hotter than you need to. Around 175 degrees is enough for most things. Every degree above that speeds up the breakdown of the oil.
Put the lid on once the pan has cooled. That keeps out dust and light, and oil is spoiled by both.
Frequently asked questions
Can I use vinegar instead of soda crystals?
Not for grease. Vinegar is an acid and it works well against limescale, so against that white haze on stainless steel. Grease asks for the opposite: soda crystals are what break the fat down. Use both, but for different problems and never at the same time.
Why does it fizz when I mix soda crystals and vinegar?
Because the two cancel each other out. What you are left with is mostly water, a little salt and carbon dioxide that fizzes away. The two things you actually needed have gone. It looks powerful, but it is the opposite.
What is the difference between soda crystals and bicarbonate of soda?
Two different substances. Soda crystals are sodium carbonate and the stronger of the two, which is why grease breaks down fast. Bicarbonate of soda is sodium bicarbonate, also sold as baking soda, and it is a good deal milder. For a thick layer of fat you reach for soda crystals.
Can the inner pan go in the dishwasher?
Only if the manual for your model says so. With a non-stick coating, washing by hand is almost always better: the dishwasher salt and the high temperature leave the coating dull. The appliance itself, with the heating element, never goes in water or in the dishwasher.
How often should I change the oil?
That depends on what you fry and how hot. A good gauge is what you see and smell: if the oil goes dark, foams at the edge or smells rancid, it is finished. Straining after every session stretches it out considerably.
My deep fat fryer is brown on the outside. Will that come off too?
That is settled grease that has baked on. Make a paste of soda crystals with a little water, spread it over, leave it for an hour and then wipe it off. If it has been there for years, count on two or three goes. That is not the method failing, it is simply a thick layer.
My kitchen smells of frying for days. What do I do about that?
The smell sits in the settled grease, not in the air. As long as that film is on your tiles and cupboards, the smell stays. Airing the room helps for a while, taking the film off helps for good.
PFAS-free pans too
Deep frying is not the only thing that gives the coating on your pan a hard time. If you are after a pan that can take heat without the non-stick giving up after a year, you can read on here: how a pan without PFAS works. And if there is still a burnt pan sitting on your worktop, this is how you rescue it: how to clean a burnt pan.