Goldstone is one of those materials that can added to glass for some extra sparkle. It consists of copper filings suspended in clear glass. If worked too hot in a direct flame it will appear to be rust colored or brownish instead of sparkly gold. I've been very pleased with the goldstone I've been using. I heat chunks of it in the flame, case it in clear that is the proper COE for the glass I want to use it with, and pull it out into stringer. I just love the glittery results!
1 year ago