Bluing

Bluing may refer to:

Bluing (steel)

Bluing is a passivation process in which steel is partially protected against rust, and is named after the blue-black appearance of the resulting protective finish. True gun bluing is an electrochemical conversion coating resulting from an oxidizing chemical reaction with iron on the surface selectively forming magnetite (Fe₃O₄), the black oxide of iron. Black oxide provides minimal protection against corrosion, unless also treated with a water-displacing oil to reduce wetting and galvanic action. A distinction can be made between traditional bluing and some other more modern black oxide coatings, although bluing is a subset of black oxide coatings.

In comparison, rust, the red oxide of iron (Fe₂O₃), undergoes an extremely large volume change upon hydration; as a result, the oxide easily flakes off causing the typical reddish rusting away of iron. "Cold", "Hot", "Rust Blue" and "Fume Blue" are oxidizing processes simply referred to as bluing.

"Cold" bluing is generally a selenium dioxide based compound that colours steel black, or more often a very dark grey. It is a difficult product to apply evenly, offers minimal protection and is generally best used for small fast repair jobs and touch-ups.

Blue rinse

A blue rinse is a dilute hair dye used to reduce the yellowed appearance of grey or white hair, typically associated with older women. In a manner similar to laundry bluing, the blue rinse can make yellow-white hair appear blue-white.

The blue rinse gained popularity after Jean Harlow's appearance in the 1930 film, Hell's Angels.Queen Elizabeth also contributed to the popularity of the blue rinse in the 1940s.

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