Blueing

[Dwight Gruber]

Curt,

To expand on Tom's answer a bit, the "area" to which you refer is the sear spring. On a Luger (pre-1937 Mauser) all the flat springs, the axle pins, the front sight, and the grip screws are "fire blued". This is a natural result of heating white steel to a temperature of about 560�º-640�º F, depending on the color and tempering of the steel desired--the parts differ in their color in this respect. Fyi, the straw found on small parts is accomplished the same way, but straw color occurs at about 440�º-460�º F.

You may be familiar with the effect as seen on new motorcycle exhaust pipes at the cylinder head. The hot exhaust gases at the head turn the pipe very dark and intense blue, and as the gases cool as they pass through the pipe the full spectrum of heat coloring can be seen until they reach a distance where they are no longer hot enough to have an effect on the metal.

--Dwight