In a water- insoluble form, the dye was then locked into the protein. Sweating consisted of hanging, or placing, the goods in a chamber with steam. In the presence of air, the carbonate or oxide form of the metal results. Dyes are soluble in some type of a solvent. Mineral pigments are not soluble in a solvent.
Copper is an effective bacterial inhibitor.
To most insects and worms copper is a potent toxin. By impregnating the protein with certain metallic compounds the protein becomes toxic to most life forms which would use it as a food source. Since the metal lic compound is insoluble and chemically bonded to the protein it will not be toxic to the user or wearer. Until recently, the mineral pigment dyes and mordant dyes using a metallic compound were the only means available to protect wool and silk against insect attack. Mineral pigment dyes are noted for extreme durability.