Oxidized /Copper Sterling Silver
Oxidizing copper or sterling silver changes the surface of the metal making it oxidize at a faster rate to obtain the grey/black finish. This treatment does not change the structure of the metal but the matte black surface finish will wear off over time depending on the how much direct contact it has with the skin and clothing, exposing the natural colour of the metal underneath. To help prolong this surface treatment I use renaissance wax coating, but it this only prolongs the life of the colour and will not last forever. I recommend avoiding cleaning the surface of any oxidized piece particularly with any jewellery cleaners as this will remove the treatment.
It is important to treat the work with respect and care, this will in itself keep your piece in its best condition possible.