Q: I have read that both copper and sterling silver can be oxidized using Liver of Sulfur or ammonia. During the oxidizing process, both metals will go through a range of color changes before getting to the antique-look. My question is: are you supposed to use some kind of sealant on all pieces that have been oxidized BUT not to the point of the antique-look. For example, oxidizing copper until it turns blue. None of the articles that I've read mention use of sealants. Thanks very much!