Cold blue on a Krein blade

C

clockman

Joined
Jan 14, 2009
Messages
3,176
Has anyone tried with good results to cold blue a Krein black blade ? I know
cold blueing will not work on stainless steel.Will cold blue work and say on
cpm 4?
What about other cpm non stainless steel...will cold blue work?
What kind of solvent is used to clean the blade before blueing?
I used to be able to touch up gun parts using mineral spirits and 4440cold blue.



Thanx Craig
 
I have not had any good experience with cold bluing knives. I used a cold bluing agent on a Cold Steel Carbon V Twistmaster which had more sever rust issues after the cold bluing than it did before the application.

I would not chance ruining one of my Krein knvies with any such treatment, but to each their own.

If you decide to do it, please post pics so we can see the outcome.

Good luck!

Doug
 
Cold bluing is a pretty dicey proposition, and I really don't like bluing on a knife blade anyway.

But the best of the cold blues are Van's Instant Gun Blue and Brownells' Oxpho-Blue, which I believe are chemically just about the same and work in a completely different way than all the others. The others I know use copper to achieve their rather dull, muddy, pseudo-blue coloring, and I'm assuming sulfur from the smell they leave, plus they actually tend to promote rust. Van's and Oxpho on the other hand inhibit rust, and can produce a decently polished, consistent appearance, albeit not as deep as a good hot blue. Van's and Oxpho are more durable, and even touch up better.

But still the reality is, bluing never looks good on a surface unless it's very consistent, either polished, or brushed/bead blasted. And knife blades ... well, they get scratched and scuffed 'n stuff. But if I were going to try it, I'd go with the Van's, or Oxpho. If you give it a go, I hope you'll let us know how it works out and hopefully give us some pics. Others have asked before, I've never seen any follow-up; I assume the results were not favorable.

But like Chapman, I wish you good luck!
 
Here's a tip for cold bluing. The steel needs to be surgically clean - no oil whatsoever. Acetone works well for this. Very quickly get the metal warm before applying the cold blue, just warm enough that it is uncomfortable to hold onto (a hair dryer will do)(don't touch it with your bare fingers or you will need to degrease again)After applying let it set for a minute or two and wipe off with a clean rag. Now it needs to be carded with either a very fine soft wire brush or some very fine grit Scotchbrite with light pressure. Now put the smallest amount of cold blue ( a couple of drops) on a clean rag and rub it vigorously onto the metal. Repeat this several times and the finish will get darker and start to build up in thickness. Play around with it. If the steel has very much chrome content you won't get a good dark color. Oil the metal immediately after applying and buffing out the bluing or it will start to form brown rust on it. It makes for an attractive finish but will not wear as well as a factory applied hot blue finish and must be kept oiled.
 
As a gunsmith I second the recommendation for Brownell's Oxpho-Blue. I've done many a gun job with it for years and it works great. Here's my technique:
1. I sit down with a propane torch lit at my right side. I run the barrel and/or action back and forth through the flame until it's almost uncomfortably warm. The hair dryer tip would work just as well. The heat, IMO, does a couple of things for you. It 'burns' off any oil residue and also opens the 'pores' in the metal to accept the bluing.
2. Dip a rag or cotton ball in the bluing solution and 'slop' it on the heated metal. Don't worry about neat, just get a good coat on the steel. It will dry very rapidly and turn a smoky blue-grey color. Set the treated metal aside and polish with triple 0 steel wool several hours later. Repeat the treatment if you think necessary. Usually it isn't.
3. BTW, avoid breathing the fumes from the bluing solution on the warm metal.
 
Funny I just cold blued a old bird and trout knife last night. As far as technique goes everything was already pretty much covered. However unlike a few that posted I really like the look of a blued blade I think it looks better than a conventional patina. Much more uniform and a more deep tone. It also really helps with rust prevention. I would second the advice on oiling the blade right after you finish the whole process and give it a light coating every week or so. Good luck and post pics please. I'll try take some pics of my project tomorrow after work.
 
Try acid washing the blade before you cold blue it, vinegar works for this if you don't have a real acid bath. It seems to give a more consistent blue for me and increases the rust resistance.
I think Parkerizing is a more durable and practical finish for knife blades though and is not very difficult to do at home.
 
You must log in or register to reply here.
Back
Top