USE EXTREME CAUTION IN EMPLOYING THE FOLLOWING PROCEDURE! The following protective gear is highly recommended. These should be resistant to nitric and sulfuric acids: rubber coated splash apron, gloves, safety glasses and an acid storage cabinet.
The ideal method for cleaning diamonds uses the acid bath. A mixture of 1 part nitric and 2 parts sulfuric acids in a small beaker over heat will clean the diamonds thoroughly. Even the smallest particles of metal shaving and dirt will be removed in such an acid bath. The color of a diamond can often be dramatically improved, perhaps due to a pitted girdle that has collected grime over years of wear, or a cutter who did not clean the diamond properly after the final polishing process. After a small amount of the solution has been mixed in a small Pyrex beaker -- 20 to 50 milliliters (depending on the quantity of diamonds to be boiled) -- under an exhaust fan or outdoors, and the diamonds have been dropped in it, place the beaker on your heating device, such as a hot plate. Heat the solution until it boils for about a minute or longer, depending on how soiled the stones are.