Do the salts actually cause a chemical change (aside from changes due to temperature) on the surface of the metal, or are they used more or less as a media to convey an even temperature distribution? For example, when bluing a small screw, would I get the same result whether I flame blued or nitre blued it?


Also, from what I read, it appears nitre bluing has issues with wear. Would it last on a rifle's butt plate or trigger guard?


FWIW, the project is a Krag M1898. All my research leads me to believe the barrel needs to be rust blued, receiver is "oil blackened" (that's going to be another science project), and most of the small parts are nitre blued.


I'm just not comfortable with this nitre bluing idea yet.

Rock, I've blued hundreds of guns but have not used the nitre or oil methods. In fact I had to look in my 1933 edition of "Modern Gunsmithing" to find out what they are. I blued using the black oxide hot dip and Belgian rust methods. I think for your purpose the Belgian method might suit you best. I cannot recommend flame blueing because the part may warp or lose temper.

Brownell's sells their brand of Belgian blue they call Classic Rust Blue. It will require an iron or steel pot (not aluminum) large enough to totally submerge the parts you want to blue. If small parts and screws are all you want to blue you can do it on your kitchen stove. Follow the directions carefully and you will get a very nice blue.

If you want to go with black oxide hot dip method check with your local plating shop. They may sell you a small amount of salts to use to do the jobs you asked about. Do not ever try to blue aluminum using this method as it will desolve aluminum. I found this out the first time I blued a gun. Luckily it was my own .22 rifle. Also, this method is not something you can do in the kitchen.

Blueing is not intended as a protection against rust. Blueing itself, no matter the method, is a rusting process and is only about .0004" deep.

[This message has been edited by Msgt USAF Ret (edited 10/7/2011 3:11p).]

Thanks, MSGT.

I'm already planning on buying Brownell's "Classic Rust Blue" for the barrel. Depending on what it looks like, I might do the small metal parts with it too.


Here is the nitre blue I was questioning http://www.brownells.com/.aspx/pid=1105/Product/NITREBLUE-reg-BLUING-SALTS.

I just found the instructions http://www.brownells.com/userdocs/learn/Inst-362%20Nitre%20Bluing%20Bluing.pdf, so that'll give me some more reading this evening.


As far as the blackened receiver goes, I don't think it's supposed to be as dark as a black oxide finish. The color it had new was a result of the oil quench it received in heat treating. I'm hoping that I can somewhat duplicate this by warming it to 200F (or less) and submerging in used motor oil. Kind of like seasoning a cast iron skillet on a much dirtier scale. This sounds dumb, but it's free and it migth work. If it doesn't I don't know what I'll do. I might try browning it and lightly sanding. I did this on my muzzleloader and it has an appearance similar to what I'm after.


I appreciate any more advice you may have.

The process of nitre bluing from Brownell's is basically the same as described in my book but my book does not have the many safety precautions. They say the way yo test to see if the nitre is hot enough is when it will ignite a pinch of saw dust, interesting. Actually the whole process is interesting.

The receiver may have been color case hardened originally. I would not rcommend doing this because it WILL lose it's temper.

I have used Herter's and Brownell's Plum Brown to brown some antique arms before and it works about the same as Belgian blue, tedious but worth it.

Remember that no matter which process you use the finish/polish you start with is all the finish/polish you'll end up with.

I would be happy to loan you my book if you would like to read it. It's interesting to see how they did things back then.