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Heat coloring steel. How to keep color?

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  • #16
    Re: Heat coloring steel. How to keep color?

    [QUOTE=CarWiz;54018]You might check with a gunsmith that restores antique guns. Some of these were tempered in nearly a rainbow of colors. The process used to use some pretty nasty chemicals but check if there is a modern copy of the process. The process was actually used as a case hardening step. Here's an example of a Stevens 44. [QUOTE]

    Don't confuse the two processes. He wants to fire blue--you have color case hardening. The modern "case" is just a chemical treatment to look like the original; gun blue remover will strip it right off. To color case harden you need wood charcoal, bone charcoal (in the correct mix), a crucible and a temperature controlled oven.

    What happened on the shift knob was that it was NOT heated evenly. the yellow was about 400-deg. F; the blues come in at about 700-deg. You have to go slowly to keep the heat even.
    Nitre bluing is similar but can be dangerous. You put the part in molten salt petre (about 700-deg F) until it changes, then quench in water. Water must be below and away from the mixture or you can get a heck of a burn from the nitre. There are a FEW gunsmiths that do this. It is not cheap.

    Back to fire bluing. I do it to gun screws. Don't do it in sunlight; you cannot see the colors well. You have to anticipate what color change will hit by the time you hit the quench. You are "chasing" the color!

    You need a high polish to really see it happen. It must be clean.

    Originally, it was quenched in sperm whale oil. THE best substitute now is full synthetic motor oil. Leave it there for a while.

    If you want to coat it, I'd try automotive clear coat. Not the rattle can stuff. Absent that, it will wear off, but it is pretty tough.

    If you miss the color, just clean it then polish it again.

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