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Nitre-blue can anyone explain its use??

Discussion in 'Shop Talk - BladeSmith Questions and Answers' started by jff428, Aug 5, 2012.

  1. jff428


    Dec 23, 2011
    I see alot of damascus now is fire blue when I looked into it I found Nitre-blue referance.
    How is this done? The info says you heat the solution to 600 degrees .Wont that ruin the temper
    of any steel you use ? So can anyone explain the process and prep ?I really like the look but am not
    sure how its done. Also what prep is needed on the damascus before applying this product? Or am I
    looking at the wrong stuff? Thanks:confused:
  2. Stacy E. Apelt - Bladesmith

    Stacy E. Apelt - Bladesmith ilmarinen - MODERATOR Moderator Knifemaker / Craftsman / Service Provider

    Aug 20, 2004
    You heat the salts to 550-600F and immerse the blade or hardware in the molten salts. It is only in there for a few seconds, so it does not ruin the temper. The change is almost instant. Use a sturdy wire hook to dip the blade or fitting in and out.
    If held there longer than a minute it could soften things a bit. However, 1095 that was fully hardened will be at Rc 57-58 if held at a 600F temper for an hour. There is no real worry about temper embrittlement with niter bluing, as the soak is far too short ( and temper embrittlement is not really a knife issue).
  3. Rick Marchand

    Rick Marchand Donkey on the Edge Moderator Knifemaker / Craftsman / Service Provider

    Jan 6, 2005
    About 3-4 months ago, I was all worried about tempering embrittlement. Turned out to be a non-issue... real... but there are much more prevalent ways to screw up a knife.

    As far as the bluing salts... I am not to educated on them. BUT I do know that I get an as-quenched hardnes of 65-66HRC with 1095 in HQK and tempering at 600F for 2hrs puts me down to 54-55HRC for digging/prospecting tools. That thin edge on your knives must be getting over tempered in a 600F bath... even if only for a minute or two.
  4. cdent


    Aug 28, 2005
    I believe Brownells has a pdf for how to use their nitre blue salts that might answer your questions. I think Rick is right though and you may have to decide on some trade off between appearance and edge holding.

    Good luck with it, Craig
  5. butcher_block

    butcher_block KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Dec 6, 2004
    while i know that tempering temp/times can vary i would never subject a "plain" steel blade to those temps (fittings are whole different story )

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