In my enameling work, I sometimes use a mild homemade pickling solution to remove firescale (cupric oxide) from copper. The pickle is a saturated solution of white vinegar and kosher salt, kept hot in a Crock Pot. After heating the copper pieces in a kiln, a layer of cupric oxide forms on the surface, which is then dissolved in the salt/vinegar solution. After a while, the solution turns a lovely blue color from the dissolved copper. If I forget to put the lid on the pot, eventually the solution evaporates, leaving pretty blue crystals that look a bit like copper sulfate. So, what have I got here? I don't want to just dump it due to the copper content. I'd like to figure out something to do with it, but first I need to know what it is. I'm thinking it might make a good electroplating solution, but that's just a guess.