Would it work? I've been making rings out of copper however, they turn green after time, obviously. At first it looked cool but it leaves a green mark on my girlfriends finger, which she doesn't like (although she refuses the take the ring off

).
Can I simply put varnish on it to prevent the rusting? It's really all I have in my shed at the moment. Anything else I can do? I don't want to buy any expensive thing off a dodgy website, it has to be something you could find in a shed or a hardware store as I have no credit card or anything.