Annealing Copper and Aluminium washers

Or, making your oil-tight washers oil-tight again.

So you've dropped the oil from your engine / gearbox / forks / bevel drive, and you realise you should have bought a new washer for the drain plug cause the old one looks a bit squashed. Will it seal again? Will you over-tighten (and strip!) the drain plug getting it to seal?

Better to re-anneal the washer if you are going to re-use it.

Why? - When you 'work' copper or aluminium, it goes hard. Tightening an oil-drain plug against a washer 'works' the metal. 'Annealing' means 'making it soft so it deforms again'.

Here's how....

Grab 2 pairs of pointy-nose pliers. Wipe any oil/grit off the washer and take it into the kitchen. Erm, you do have a gas cooker, don't you ?

(Alternatively, gas welding kit; blowtorch; or some other source of safe flame. A cigarette lighter isn't enough heat, a hot air gun won't do it either. A gas cooker is the thing you want. A camping stove will do.)

You need to get it hot enough, but obviously not melt it:

Copper: which you recognise because it is copper-coloured.

You need to get copper 'dull red'. Dull Red is one of those technical terms engineers use. It just means roast it until it glows a dull red. In order, as you heat metal, it goes:

  • slightly reddish tinge - this isn't hot enough to do anything
  • dull red
  • cherry red - properly 'red', but somewhere less than orange
  • orangey-yellow - way further than you need to go
  • white-hot - its about to melt, stop it.

Aluminium: which is not copper-coloured, it is grey.

Wipe washing up liquid on it. When you heat this, it boils, then burns to a black deposit. That's the heat at which its done. (Alternatively, you can cover it with soot from a sooty flame, then when this soot burns off, you are done. But Fairy Liquid is easier.)

So, using one pair of pointy-nose pliers, hold the washer in the flame until you get to the temperature you want. Then hold it by the other side, so you can heat the bit that was under the pliers. Heat it as evenly as you can, and for something as small as a washer, it can take as little as seconds, so pay attention.

Once it has been cooked all over, let it cool down naturally. You don't need to quench it in water or anything.

Note well. You want 2 pairs of pliers. ITS GOING TO BE HOT, so you don't want to touch it with your fingers. DO NOT let it touch exposed skin. DO NOT lay it on the kitchen table to cool down.

And that's it, your washer is 're-annealed'. Brush off any sooty deposits, refit it to the bike and it will form itself to a tight seal again. You can stand back and feel all smug and pleased with yourself :)


Did you burn yourself, you muppet? Stick the burn under the cold tap for 10 minutes. Butter is an old wives' tale and doesn't help. Leave it under the tap as long as you can stand, at least some minutes. Broken skin, treat with antiseptic cream and a sticking plaster.

You don't want to re-anneal washers more than a few times. The metal will take it, but after you've softened and squished it a few times, it's probably getting a bit thin and deformed. It may start to be loose on the drain plug, so it may not be seating against the faces the manufacturer meant it to. If you notice this, get new washers for the next oil change.

This annealing process works for copper and aluminium washers. In fact, the process is the same for any non-ferrous (non-steel) metal. Copper or Aluminium are what your oil-plug drain washers will be made of.....

.....unless you have a really old bike which might have fibre washers (look like reddy-orange fibreglass, hard felt, or tarry cloth). Just re-use until they crumble.

.....or what are often known as 'Dowty Washers', metal washers with a rubber insert. Re-use until the rubber becomes worn, damaged, or hardened with heat/age.

You do not need to anneal new washers. They come out of the manufacturing process soft and ductile. You only need to re-anneal used washers that have been worked.

If you are doing a copper gasket as opposed to a washer, perhaps a cylinder head gasket, some people like to cool by quenching in water. Drop it in edge first for quick, even quenching. Quenching isn't strictly necessary, the rate of cooling makes no difference to the resulting softness. For something as mission-critical as a head gasket, you only want to re-use it in an emergency, but it would certainly help the seal if you can re-anneal.

The annealing process does not soften steel washers. If you heat and cool steel - it gets hard and brittle.