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, by heat produced colors can also be produced 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.[1][2][3]
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.[4][5]
Heat coloring of metals is probably the oldest method of coloring metal objects.[6]
Examples
Heat coloring of iron and steel
straw yellow/232 C brown/265 C purple red/277 C light blue/288 C dark blue/293 C[7]
Heat coloring of stainless steel
light yellow/290 C brown/390 C magenta/450 C blue/540 C dark blue/600 C[8]
Heat coloring of titanium
pale gold straw/385 C purple/412 C deep blue /440 C red purple/565 C light green/510 C brown gray/648 C green blue/925 C[9]
Heat coloring of copper and its alloys
Heating to a temperature of 161-341 C produces various interference colors[10]
Literature
- Hiorns, A. (1907). Metal Colouring and Bronzing. London: Macmillan and Co. OCLC 3757279.
- Kaup, W. J. (1914). Metal Coloring and Finishing. New York City: Industrial Press.
- Field, S. (1925). The Chemical Coloring of Metals and Allied Processes. London: Chapman & Hall, Ltd. OCLC 2922065.
- Fishlock, D. (1962). Metal Colouring. Teddington: R. Draper. OCLC 3982659.