Nitre Bluing/Fire Bluing - Restoration

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JG727

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I'm a gunsmithing student at Montgomery Community College in NC.
For my 21st birthday present to myself I bought an old Colt 1903 in need of a lot of TLC. The slide will probably need replacing, and the whole gun needs to be refinished.
I really like the Nitre bluing that you see on some of the small parts of the original Colt firearms. Is there a method that reproduces this brilliant finish that is more resilient?


An example of what I am talking about can be seen here:

1903ph_106716a.jpg

http://www.coltautos.com/mmst_iii.htm

Related question: Is this Nitre Bluing or Fire Bluing? I keep finding conflicting answers.

If it Fire Bluing, can anyone offer instructions on the proper way of attaining that finish? Or information on companies that provide this service?
 
There are a couple youtube videos that will give you a basic idea of nitre bluing. You melt the salts and pay close attention to the temperature. Different temperatures and lengths of exposure to the salts give different colors, for instance parts of certain lugers were straw yellow from nitre bluing, as opposed to the colors you have there. I believe that the brighter blue colors like that are on the upper end of the salts temperature scale. You have to be careful not to use parts that have a temper that can be ruined, or you need to keep a close watch on the thermometer. It looks like the stuff that was nitre blued on that gun isnt anything with a temper that could be ruined. I believe this information to be correct, but I read up on it a while back.


If you're a gunsmithing student I'd say just pick up a kit from brownells and try it. Just read up on it a bit, or get those videos. Or ask around, an instructor might be willing to take you through the process.
 
Asked the instructors, they don't know. the library at school has some good books on finishes, but most of the books are either old, or reprints of old books. The science hasn't changed, but the availability of chemicals sure has.
 
The science hasn't changed, but the availability of chemicals sure has.
Click to expand...
That's true. They are now much easier to obtain.<http://www.brownells.com/.aspx/pid=1105/Product/NITREBLUE-reg-BLUING-SALTS>.
 
JG727

Apparently you are not talking chemical bluing but fire bluing by pure old heat.
Here is a video. The results are not impressive because the screw head was not polished to a mirror finish. This very important. I sand with 800 grit and buff to mirror finish.

It will take some practice and you can achieve different but pleasing results. I have found that if you heat the threaded portion first and slowly walk the heat up the screw/bolt, the entire head will go from golden to purple to blue at once. Quickly quench in heavy oil.
The bigger the part, the more difficult to achieve the beautiful blue you desire. Surprisingly, foiled attempts sometimes results in a beautiful and different finish. Sometimes you will go past the blue desired and the results are not satisfactory. Simply buff and do it again.
 

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you heat the parts up in saltpeat to about 600-700 degrees that youtube vidio is great and brownells sells the chemical.that little blue is at about 700 degrees.
 
Fire bluing does not need any chemicals. The metal, when heated uniformly,
will turn from wheat to blue in a few seconds. Normally when a small part of the screw top is wheat colored and the blue has almost spread across the bolt head quench it in oil and it will capture the blue. A light buffing with a clean rag or paper towel will do the final job.
 
That is interesting. I would devote the salt baths to the larger items to fire/nitre blue. The screws and other smallitems can be fire blued in a lot less time.
400-600 grit is a little coarse. When I buff a screw and it has some rough spots, I spin it with a drill using 1000 grit. Then I buff to a mirror. Makes it super shiny with color.
 
Don't do it to heat treated parts, cause they won't be when you get done fire bluing them!

rc
 
rcmodel said:
Don't do it to heat treated parts, cause they won't be when you get done fire bluing them!

rc
Click to expand...

I'm new to this and drinking from a fire hose.

At what temp do you question the integrity of the piece? I've got an old Stevens 12 gauge that I want to re blue (it's a mess). Can I use this process without compromising the barrel?
 
NO.

Fire bluing requires a temperature high enough to turn steel blue, or about 570 degrees.

Any heat treatment at all would be rendered null & void at that temperature.

Not to say your old Stevens barrel is heat treated in the first place?
But I most certainly would not do it to any barrel.

Fire blue is the least durable firearms finish there is anyway.
It would wear off a barrel before you got real done doing it.

rc
 
I've been poking around some other threads and might try cold bluing as a first try. The gun's not an heirloom nor a pricey one so I'll at least learn something in the process. Thanks for the info!
 
The screws that are heated to fire bluing temps are quenched in some liquid restoring some of the hardness. I use used diesel motor oil. Quenches quicker and traps the blue instantly. Uberti screws are probably the softest there is and after fire bluing, they will withstand a good screwdriver admirably. A bunch of us usually mess up a screw head or two cursing the 800 pound gorilla that tightened them in the first place.
Not much fire bluing you can do to heat treated stuff. Usually too big. The butt plate on a '73 will fire blue nicely as will scratched up side plates.

That bead blasted SA would look purdy with fire blue screws.
 
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