One thing about rust blue solutions is, there are a ton of recipes out there. I always heard that the German version of rust blue was not written down, but who knows, the color of rust blue varies like the colors of the rainbow...........everyone has a favorite hue.
Another is that the home guy can do it, whereas the hot blue takes a lot of setup and dollars, and disposal of used product. In rust blue, one will soon learn about a fine stainless carding wheel.
Most rust blue solutions demand cleaniness, any dot of human oil, and there is a spot in the blue. Some of the more recent solutions have a detergent in the solution, hence no need for white gloves etc. Of course, desired results as to color etc, may guide you to a specific solution to use.
I was always amazed at the areas on the early Lugers left in the white. Solution for rust bluing is put on so sparingly, that it is easy to control; but on the other hand it can be removed mechanically or chemically as well. Some guys plug the bore, some do not. Guess it boils down to how your were taught and the results thereof.
Rust blue guys can talk hours on end about technique within their own inner circles. Some dilute the solution for a finer grain attempt, some polish to high polish, some to less than 400 grit. Sweat boxes even come into the talk.
Maybe the choice between rust blue and hot blue is somewhat in tenure, I can do a form of rust blue myself and take some pride in being able to do it myself; but if I had to do thousands of such, hot blue is the ticket or stainless.
Done properly, rust blue is the cats.
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