Heat coloring of metals

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Heat coloring of metals is a relatively simple process that, in principle, produces interference colors on the surface of the metal. The colors depend on the temperature to which the metal is heated. The most obvious example is thermally produced colors on steel, of which blue coloring is most commonly used. In addition to steel, colors can be produced by heat on copper and its alloys, nickel, chromium, niobium, titanium, and tantalum. Heat coloring of metals can also include procedures for obtaining brown or black color by gradually heating objects made of gilt copper (also known as vernis brun) or steel coated with linseed oil to 300–400 °C. This process also includes the Bower–Barff process and related processes, in which the steel is heated to 800 °C and exposed to highly heated steam.

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