In the metalworking industry, tarnishing refers to a change in the metal surface. This is caused by the deposition of a thin layer of foreign material on the respective metal. The metal usually changes to a dark color, which can be caused by various environmental influences such as temperature, light or chemical compounds. The method of tarnishing itself varies between the different types of metal. Silver tarnishes due to the influence of sulfur in the air. An oxide layer is formed. This oxide layer also forms on steel, but due to very high temperatures to which the jewellery material is exposed. Through the process of tarnishing, steel loses its metallic shine and changes color to slightly red, yellow or blue shades. The metals zinc and lead also tarnish if they are exposed to particularly high humidity. This is in contrast to the precious metal gold. Gold does not tarnish and retains its stylish shine over the long term if the fine gold content is sufficiently high. However, the higher the metal content of a gold alloy, the more likely it is to tarnish, since metals also react within alloys. When gold and a metal, such as copper or silver, fuse together in this way, gold can also change its metal surface.
