blueing

The heat treatment of iron or steel which forms a thin surface layer of blue oxide. This retards rusting, and was also used to decorate armour.

Blueing

In decorating, the term blueing applies to the adding of a small amount of blue to certain white pigments or paints in order to neutralise their yellowish tint and make them appear whiter.
Found on http://www.probertencyclopaedia.com/browse/TB.HTM

blueing

The heat treatment of iron or steel which forms a thin surface layer of blue oxide. This retards rusting, and was also used to decorate armour.
Found on http://www.antique-marks.com/antique-terms-b.html
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