How to Anneal Copper Washers

Annealing copper washers makes them soft again so they can do their job.  Some people even recommend annealing copper washers before the first time they are used, as storage can cause oxidation hardening.

Annealing makes copper washers seal properly.  Copper washers can be reused virtually forever when they are annealed before each tightening. Copper washers get hard over time so simply putting them back in after a rebuild can lead to leaks.  It is a drag to have a fresh engine leak from the head nuts.

The process is simple, heat until it glows red, then let it cool slowly in the air.  Some confused people advocate "quenching" the washer.  Quenching, immersing in liquid, is a way to make hot metal harder.  We want our copper washers to be soft so they can form a good seal.  That's why we let them cool gradually in the air.

Here's a YouTube showing how it's done.