This is what I read somewhere:
If you want to seal copper from additional oxidation patina, I would recommend the following product:Permalac. You can purchase this product by the gallon or in spray form from Peacock Laboratories.
And here is where you can buy it. The EF type is environmentally friendly: https://www.sculptnouveau.com/Details.cfm?ProdID=46&category=7
Must give this a try....after I patina my pieces so that it does not patina anymore.
6 hours ago