Hi all As a chemist with over twenty years of teaching experience, I just wanted to clear up an incorrect chemistry statement in the following post: In a message dated 9/4/04 12:03:41 PM Eastern Daylight Time, [email protected] writes: What About Using Graphite? Graphite is a carbon substance. Graphite is used in pencil lead and carbon paper as well as in batteries because graphite contains Sulphuric Acid. Sulphuric Acid is a heavy CORROSIVE oily oxidizing and dehydrating agent. I think corrosive explains enough on why not to use Graphite. We want to save these stones not have them fall apart in our hands. Graphite DOES NOT contain sulphuric acid. Car batteries contain sulphuric acid in the solution surrounding the electrodes. Graphite is one of the elemental forms of the element carbon. It only contains the element carbon. It is not corrosive in a chemical sense, but it is abrasive and may cause damage by that method.