Jump to content
I Forge Iron

gun blueing a knife


Recommended Posts

index.cfm?fuseaction=user.editAlbumPhotohey yall i finally made my first knife with tools in a woodworking shop, my grandpa suggested blueing it with some gun blue and a propane torch, it worked the first time...sorta we heated it up to much and tried to apply the blue, but it wouldnt take, so we splashed a little water on it and tried again, it gave the knife this beautiful blue sheen but it also had some blueish black smudges that looked like grease residue almost. I got most of it off but i cant figure out how hot to get the blade next time, or how to tell if its hot enough Edited by TexasIronworker
Link to comment
Share on other sites

hey yall i finally made my first knife, my grandpa suggested blueing it with some gun blue and a propane torch,.....out how hot to get the blade next time, or how to tell if its hot enough


That certainly is an interesting application of a finish, but possibly shocking to individuals who in the process of making knives are concerned about the knife's heat treatment and ability to hold an edge. You might want to:

1) focus on how to properly heat treat the steel for the blade.
2) at least at this point in your stage of learning about knifemaking, plan on using a cold-blueing process after the blade is heat treated so as to maintain the heat treatment of the blade, or use a more traditional knife finish.
Link to comment
Share on other sites

If you want a true gun blue finish I think that you can buy bluing salts from Brownells, at least 30 years ago you could, so you may want to Google "bluing salts" to see who sells them now. Hot bluing is usually done in tanks of boiling caustic salts that slowly turn the steel blue. It has been a while since I have hot blued anything but the most we ever did with anything that came in a bottle was warm it up with a heat gun to just about the level of "uncomfortable" to hold and then apply the cold bluing solution. I suggest you read the directions again.

Link to comment
Share on other sites

That certainly is an interesting application of a finish, but possibly shocking to individuals who in the process of making knives are concerned about the knife's heat treatment and ability to hold an edge. You might want to:

1) focus on how to properly heat treat the steel for the blade.
2) at least at this point in your stage of learning about knifemaking, plan on using a cold-blueing process after the blade is heat treated so as to maintain the heat treatment of the blade, or use a more traditional knife finish.


we heated it to red so about 1000degrees and quenched it in motor oil, when we blued it it never changed color. would that have affected the temper
Link to comment
Share on other sites

we heated it to red so about 1000degrees and quenched it in motor oil, when we blued it it never changed color. would that have affected the temper


As I am sure you read the knife sticky's on heat treatments, you know that 1000F is fine if you used H13, you did use that correct? :o
Link to comment
Share on other sites

By "did not change colors", you mean it never got "red hot", right?

Thing is, if you had it polished bright when you hit it with the torch, you would have seen oxidation colors run thru the steel... straw, bronze, purple-ish, blue, etc. This would have shown you the temper of a particular steel. Depending on the steel, if you exceded 450 degrees, you might have "lost your temper"... blade too soft. More in some; less in others. Also, 1000 degrees might not be enough to get full hardening in most steels.

Seriously, read all you can first. There is a ton of information here to address your problems. I promise it will all make a lot more sense.

If you're set on a blued blade, a lot of these guys use cold-blue on knives. You might look into that.

Link to comment
Share on other sites

Everyone else has commented on the judicious application of heat so all I will add is that Brownell's sells two good cold blues - one is Oxpho and the other is Dicropan. The Oxpho is a very good product and works well to cold blue a carbon steel knife (without applying heat)

Link to comment
Share on other sites

I've seen a good many damascus art knives hot blued, but from what I understand the temps used to blue causes a little edge holding loss. Not sure how much exactly.

I've used Birchwood Casey super blue and like it for some damascus, realy improves the contrast, and no heat.

Link to comment
Share on other sites

I've seen a good many damascus art knives hot blued, but from what I understand the temps used to blue causes a little edge holding loss. Not sure how much exactly.

I've used Birchwood Casey super blue and like it for some damascus, realy improves the contrast, and no heat.


The hot bluing causes absolutely no edge holding loss.
Oxynate 7 hot bluing is done at 292 degress. Only 80 degrees more than boiling water.

15944.attach

Edited by mod07
Link to comment
Share on other sites

I haven't used it yet, but a friend just sent me some Blue Wonder gun black. Their website is Bluing and Protection. I can't vouch for how good it is. I haven't checked out their site yet either. I just saw this thread and thought I'd see if I could learn a thing or two before I applied this stuff to my blade. Maybe this stuff can help you out.

Edited by mod07
Link to comment
Share on other sites

Thanks, it's been sold for a while now though. With normal damascus, especialy the higher layer stuff I don't blue, but with mosaics I like to blue sometimes due to the large low number of layers. May experiment some more when I get my shop done.

Link to comment
Share on other sites

A couple of observations.

You heated and quenched the blade, but you don't mention tempering it. If not, the blade may be too brittle to use. I have made quick general use knives out of files. After heating and quenching I polished the blade, and then reheated until I saw a dark straw to purple color. When I did I requenched the blade.

Oxpho bluing works good as a cold blue, but it grabs better if you heat the item up some first. Usually just hot enough to where you cannot hold it-NO COLOR CHANGE. When you apply the blue keep putting enough of it on so the blade stays wet. This is what we did in the gunsmith shop I worked in. Another thing that helps the blue to last longer is do not use a power buffer, hand sand the final polish. Power buffers can smear the metal and seal off a lot of the surface pores, not allowing the blue to penetrate. Hand sanding cuts the surface leaving the pores open. 230-320 grit is fine for a final polish when bluing.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...