[ithacaartist]

Leif,

Welcome to the forum, I'll try to help answer.

Bluing of any style is applied to at least the exposed outer surfaces of a gun to give it some protection from "ordinary" rust. Technically, I think all bluing is actually a controlled surface rusting. Rust bluing is a process that by repeated applications of chemicals, a film of oxide is built up on the steel, this done by hand. Dip or hot bluing is when the steel parts are immersed in a volume of hot chemical bath to create the coating. Cold bluing is a process of applying the chemicals without heat--commonly used to touch up small areas of a finish, and not as deep or durable in result.

"Straw" refers to the color that the surface molecules of a steel part turn when heated. It is a relatively low temperature in this case, somewhere around 370 degrees F. Higher temperatures yield different colors. A bit higher temp yields "fire blue", and you'll occasionally encounter parts thus treated, especially in custom work. Keep heating and you'll go through a spectrum of colors--purple/plum/violet, finally ending in black.

The heating process is arrested at a specific temperature to establish each color. To refresh the straw of a Luger's appropriate parts really helps its appearance. There are "stickies" on the site to explain all these processes in more detail.