@DC ,
Here's a paragraph from Wikipedia's Crayon Page:
"Such crayons are usually approximately 3.5 inches (89 mm) in length and made mostly of petroleum (paraffin wax). Paraffin wax is heated and cooled to achieve the correct temperature in which a usable wax substance can be dyed and then manufactured and shipped for use around the world. Paraffin waxes are used for cosmetics, candles, for the preparation of printing ink, fruit preserving, in the pharmaceutical industry, for lubricating purposes, and crayons."
If its used for Candles I don't think it works for Bow Strings.. But I guess you could always try.
Good luck!