"If you heat up the washer and toss it in a cold bucket of water while it is still hot, you have actually hardened the part."

CORRECT if the metal is ferrous. Non-ferrous requires the OPPOSITE approach.

When I got my airframe and powerplant certification back in the dark ages (1982) we were instructed to anneal copper spark plug washers by heating the metal, followed by quick cooling by quenching in water. My father, who was trained as a tool and die maker in the late forties, confirmed this procedure.

Real world experimentation might reveal that either approach results in sufficent softening for practical purposes.

Regards,

Tatra Mike
San Diego, California

1985 244 "Alfsen" (wife's car - the good one)
1984 245 "Buster" (in Seattle with the kid}
1985 245 "Cosmo" (currently at anchor in the driveway)
1985 245 "Daisy" (back seat down, full of tools, the work truck)
1985 245 "Earl (Hurray, another stick shift!)