The small metal piece which holds tobacco has become discolored, half of it has gone from silverish to bronze on the top and bottom of the outside part of the cylinder, the inside of it is almost completely bronze colored. I was wondering if there was any concern I should have over this? It doesn't appear to be residue or anything its like the metal changed color from the heat. I hope nothing came off and went into my lungs. Also if anyone knows what metal the crucible is made out of it would be helpful information.