I purchase copper in my little metal shop that I travel a long ways to go to. All the sheet copper works just fine for enameling. So far so good. But then I purchased some 10 and 8 gauge round wire, solid copper I was assured, to make some bangles from. I cleaned this copper by heating it in my kiln and quenching it. Then I solder the seam or tie a knot where the two metals meet as a cold connection. While I have realized that solder is not able to be enameled (at least not for me so far) I am using copper solder which I buy from Raw Treasures. I enamel these bangles using kyln fire. I have found out this is the not the same stuff as the sheet. If it is the same it doesn't act the same. I enamel the bangle, and take it out of the kiln, let it cool on the trivet, as it cools off, pieces of enamel start to pop off, it is really something too! It is like tiny explosions! I don't know what to make of this, why is this happening? I have asked this question before only to be told that copper is copper. Or to read my books, which I have done many times. But obviously what I thought about before is true. Not all copper is created equal. Obviously something is going on here. I suspect my copper is recycled and possibly been contaiminated? It would be interesting to know what is going on here....this particular bangle was created with 10 gauge wire and not soldered. I used an opaque Thompson Enamel on it. 1 color, straight from the jar. So it is clean. My problem being in another country is knowing if copper is really pure? Or am I wrong? If other will help with this question I would appreciate it.