Heat coloring of metals

Scale of colors obtained by heat coloring of steel.This process is known as tempering when it is applied to the hardening of tools made of steel.

The various colors produced indicate the temperature the steel was heated to. Light straw indicates 204 °C (399 °F) and light blue indicates 337 °C (639 °F)

Blackened steel test plate,oiled with linseed oil and then heated to 300 - 400 C

Titanium test plate,colored by heat

Stainless steel plates,coloured by heat tinting

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, 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]

History

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.

References

1. Jochem Wolters: Techniken und historische Merkmale des Braunfirnisses – eine Richtigstellung. In: Jahrbuch des Römisch-Germanischen Zentralmuseums Mainz / Römisch-Germanisches Zentralmuseum. Bd. 57(2010),1, Verlag des Römisch-Germanischen Zentralmuseums, Mainz 2010.
2. Theophili que et Rugerus presbyteri et monachi libri III. De Diversis Artibus: seu Diversarum artium schedula. (translation R.Hendrie ),London 1847.,p.319
3. "Schwarzfaerben". Archived from the original on 13 September 2013.
4. Silman,H. Chemical and electroplated finishes,London 1948,p.160
5. The Bower-Barff Rustless Iron Process,New York 1883.
6. Fishlock,D. Metal Colouring,Teddington 1962.,p. 64
7. Kraemer,O.P. Rezepte fuer die Metallfaerbung und Metalleuberzuege ohne Stromquelle,Saulgau 1983,p.82
8. "Heat Tint (Temper) Colours on Stainless Steel Surface Heated in Air – British Stainless Steel Association".
9. Untracht,O. Jewelry Concepts and Technology,New York 1982.
10. Untracht,O. Metal techniques for craftsmen,New York 1968.,p.419

External links

• Lewton Brain, C.: Patinas for small studios (pdf-file), 1985
• Budija, G.: Collection of formulas for the chemical,electrochemical and heat colouring of metals, the cyanide free immersion plating and electroplating (pdf file), Zagreb 2025
• Heat tinting stainless steel