Tim McCreights Complete Metalsmith offers a good green patina recipe.
You need sal amoniac, salt and ammonia mixed with water (I think it
may be a tbs of everything except the water, but my books at my
studio, so I am not sure). It gets sprayed on several times. You must
let it dry in between, so you can see and control how green the
Another green variation I learned in college- get a bucket fill with
saw dust and urine. Along those lines the cats litter will do the
same thing. Put your piece in, let it sit for a couple of days, and
then clean after removing and allowing to dry.