Years ago, I was doing a major fine craft wholesale show, and met many metal workers who were doing wonderful stuff with patina. (This was before the market explosion of do-it-yourself patina gels & such.)

One person said that not only did they get great results by putting the finished metal items in their cats' litter boxes, they discovered that EACH INDIVIDUAL CAT's urine produced a different effect!

Haven't had the urge to test THAT one, either. But maybe I'll try the glass beads in their boxes. :^)