Annealing softens the copper. Then the crush washer can be reused to help seal the drain plugs of my Series 3 Land Rover. These are 1 1/8th inch inner diameter and just under 1 1/2″ outside. Hardware stores stop at an inch. Same with car parts stores.

1. clean the washer
2. heat it with torch till the color changes and the oil is all burned off
3. plunge it in cold water
4. open up the sides from each other. I used a steak knife
5. reclean and reinstall on the drain plug