0KedaDibandion 9 years ago ReplyUpvoteUsually with opaque glass you can use whatever's handy. With cathedral (clear) or streaky, it depends on what patina you will be using. If you are going to use a copper patina, go with the copper so that the inner color and the outer match. If you're going to use a black patina, go with black; no patina = silver foil, you get the idea. It's basically designed to match whatever patina you are using so there aren't clashing metal colors. I also know plenty of people who use black on everything because it doesn't really clash with anything.