====== Blued steel ======
{{wst>image_r|Rainer_Brand_Panama_Zifferblattausschnitt|Dial segment of a [[Rainer Brand Panama Dualtime]] with blued hands}}
For **blueing** the steel parts are slowly and carefully heated ("started") to about 300°C. The metal then coats with an ultra-thin, cornflower blue shimmering layer of magnetite (Fe304).

The blueing is used in the field of watch manufacturing for the refinement ([[finishing]]) of [[movement]] parts, especially of screws and watch hands.


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