Originally Posted by
Sandycrack
I make 18th/19th century powder horns with scrimshaw. Most horners use potassium permanganate to dye horn. The more coats you apply over time, the darker it will become. It will fade in sunlight over time, but you can re-apply. It works amazing on anything containing protein. DO NOT GET IT ON YOUR HANDS OR FINGERNAILS. It takes a lot of time to get it off. You can buy it at ACE hardware and other hardware stores (or they can order it). It's not cheap, mostly because of the quantity you have to buy. Apparently it can be used to sterilize water. Some vendors who cater to re-enactors will a product called "Old Bones", which is Potassium Permanganate. Hope this helps.
Chris