My friend Graeme of Arcimboldi Studios made a post on FB where he was experimenting with Copper, Salt and Ammonia. It makes a fantastic patina.

Long strip soaked (right) overnight. other 2 place a small amount of ammonia in a small container like bottle top place in tupperware box. Sprinkle salt over brass sheet randomly and cover tupperware box for about a week. Don’t breath in:-)

I’m wondering if it is possible to add a small amount of salt to a glaze with copper oxide and see what it does. Or placing small salt crystals on wet glaze. The box of things to try is miles deep.