Many inlaid objects use a dark material in engraved or recessed backgrounds to heighten contrast with brass, silver, gold, or copper. Museum records may say black compound, niello, or black organic substance depending on analysis and certainty. The page should avoid treating all dark fills as the same chemical recipe.

Patination can be natural, accidental, protective, or intentional. In bidriware, darkening is essential to the technique; in other objects, later corrosion or museum polishing may change the surface. Conservators often protect evidence that earlier owners might have polished away.

Tinning coats a copper or copper-alloy surface with tin, producing a silvery interior or exterior. It can protect vessels used with food or water and create visual contrast. Tinned copper traditions remain important in many contemporary workshops, where old vessels are periodically re-tinned.