to be Gilsonite. This has long been used in formulations of paint for use on ironware as it increases the elasticity of the paint layer, allowing it to adhere to steel subjected to vibration, deformation and thermal expansion without cracking or peeling. It is also cheap, yields a glossy dark surface, and acts as a curing agent for the oil. See also Pontypool japan Rustproofing References Painting materials Ford Motor Company Paints Auto parts