Ok guys, I realize obsidian oil is supposed to be used on vulcanite and cumberland (same thing?) stems only. Can anyone explain how to identify which is which. I have several preowned pipes that after being treated with ob oil the stems changed color as soon as my saliva wetted them. Brebbia nor halcyon will bring them back to original. A list of stem materials and what SHOULD NOT be used on them seems as important as what should be used.
Stan
Stan