Jeff Blakeslee wrote:
The copper sealing washers are delivered as soft copper (annealed) and they work harden after the first use. They are not crush washers, they are plain flat copper washers that conform to irregularities in the mating surface to create a seal. Most folks replace them each use, which is what Rotax recommends.
Of course replacing them is the best, but in a pinch you can reuse one if you anneal it and then clean up the faces with some 600 grit sand paper. Annealing is simple, just heat the washer to a dull red and then let it cool naturally. This puts it back in a softer state so it will conform and seal again. See link below.
https://motoiq.com/wrench-tips-6-re-using-copper-washers/
Interesting.
Two points:
First there is a difference (at least in my mind) between a copper crush washer & a copper gasket washer. The former, usually domed/folded, with a seam on one side, actually crushes/distorts with the pressure of the tightening and should never be reused . The gasket washer, flat both sides, solid copper ring, can be annealed & reused, if you so wish. The number of reuses will be governed by the thickness of the washer, which will get slightly thinner on each reuse and may crack at some stage.
Annealing copper - I stand to be corrected, however I have always cooled the red hot copper in an oil bath. Usually the copper comes out clean, ie not oxidised/black. There will be momentary fumes from the oil bath, so do this in a well ventilated area away from flammable materials.
