The dye solution would then permeate the protein. Protein has a high affinity for acids and the dyes would bind to the sulfur ions in the protein mole cules. 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.