In my last post, I forgot to mention two things. First, yes you will definately have to coat the coin with a barrier first. With copper this could be problematic, but necessary to prevent corrosion from the RTV. Since RTV vulcanizes at room temperature there is no problem with excessive heat to the original. Second, an absolute necessity for this process is a vacuum. All the air absolutely has to be removed from the RTV in order to make an accurate copy. Patricia McElyea Curator of Collections Arkansas State University Museum [log in to unmask]