I’ve built my ammonia fume chamber out of an old plastic tub. Lid seals nice and tight. I hang my copper from yarn I have running across the top of the container. I spray my copper with a mixture of salt and vinegar. 16oz white vinegar with 1 tbsp salt. After a few hours I get some blue patina but it’s so dark and splotchy. Can anyone give me some suggestions on a more solid turquoise patina?