View Full Version : Slow Rust Blue

December 21, 2001, 08:46 PM
Did a search and found little information on the slow rust blueing process. Thinking about building a "humidity box" and would like any and all info I can get on this and the process. I have several projects started and am thinking of this "traditional" blueing instead of relying on someone else for a hot blue job. Thoughts or info???

James K
December 21, 2001, 09:15 PM
Rust bluing was used for centuries before hot salts bluing ("tank bluing") was invented. Done right, it not only is as durable as tank bluing but is (IMHO) much better looking. It is also the only way to go if restoring a firearm that was originally blued using rust blue.

As you have found, there are the slow bluing and the faster type that uses boiling water to hasten the process. I have used both and they will give comparable results if carefully controlled.

I recommend you buy an old rifle or shotgun from some gun shop's junk box and practice (a lot) until you have the system down pat before starting on anything good. Distilled water is often recommended because minerals in tap water can affect the bluing, sometimes for good, mostly for bad.

Remember, though, that metal preparation is the key to good bluing, regardless of the type used. That does NOT mean, as some gunsmiths seem to think, polishing to a mirror finish. That will work if you want a mirror finish. With tank blue, it will look fine on a Weatherby, but no factory guns were that highly polished and on anything else it will look artificial.

With rust blue, you will not get that mirror-like shine. Take a look at an early Luger, if you can find one, and you will see rust blue as it should be done.

One big advantage of rust blue is that there are almost no dangers (aside from boiling water if used) and some slight odor. Hot tank bluing can be very dangerous and the caustic salts can cause serious injury. The fumes require extremely good ventilation, too, to prevent health problems.

You can get the bluing from Brownells and it comes with instructions. A humidity box is nothing but a box, usually made of plywood, with a water pan and a couple of high wattage light bulbs. It has to be as long as the barrelled action to be blued and usually about a 1-1 1/2 feet square. Hinge one long side as a door that can open, and make the box to stand on end to make it easier to work with. One I used (not mine) had the door made
of plexiglas so the progress of the job could be seen without opening the door; I liked that idea.

The work being blued is suspended from wires hooked to the wooden plugs in the barrel, not to the gun itself. Grease and plug the barrel to keep from bluing the inside. Not a big deal if you do, but some people go ballistic if they see bluing in a barrel.


December 21, 2001, 09:32 PM
Hardchrome (Accurate Plating & Weaponry), NP3 (Robar), gold (AP&W); that's my thinking.

Why blue?

George Stringer
December 21, 2001, 11:22 PM
Because blue's prettier. :-)

There's another thread about the Gunsmith Kinks series of books. In the first volume different methods of slow rust bluing are described pretty thoroughly. There's one I seem to remember that uses wet burlap bags instead of a damp box. Good reading. You might get some ideas there. Also one past issue of the American gunsmith gave plans for building a damp box. It takes about 3 weeks to slow rust blue and about 3-5 days to use the Pilkinton's hot water rust blue. I've heard good things about Mark Lee's Express Blue but I've never tried it. George

December 22, 2001, 12:23 AM
... And, you can do it yourself. I have to remove some rust blue off my winter project, the FN Mauser .270 Resurrection... It takes several strokes with 220 grit emery paper! Tough stuff...

It's all in the metal prep. High polish hinders the bite of the acid into the steel. I recommend a fine wire brush finish or a glass peen with beads. The metal must be absolutely grease free including fingerprints. I generally scrub the rifle down with Simple green inside and out holding the gun with an inletting screw, hit it with an old hairdryer, and wipe it down generously with lacquer thinner or acetone (in a ventalated area of course). I then lacquer the bore and chamber- I find this more effective than plugging as water always seems to get in the bore anyway...

I use the Plinktons and boil in distilled water (a must around here). Build the box. No box will get you 3-4 rust repetitions and a thin finish.

I have yet to try the .0025 diameter super fine wire brush from the Brownells- this might improve my finish a bit. Anyone use this brush?

John Lawson
December 22, 2001, 07:37 PM
Yes, that wire brush is fine. Pilkington's is not ideal, but it works some of the time into an excellent finiish. I prefer to make my own. It should never take over ten days to accomplish a slow rust blue. If it does, your blueing formula is wrong or you are laying into the carding brush too heavily.
SRB is much, much more durable than any tank blue I have ever tried. No tank blue will stand up to a wire brush. There is one exception, and that is a homemade tank blue of ammonium nitrate and lye...this also stands up to a wire brush, but it is dangerous to make...clouds of ammonia gas than knock you out or worse.
I hate the very idea of a humidity box. I simply do my blueing in a small room that I have insulated. Enough humidity remains to cause the rust. If you live anywhere near water, you don't need to resort to added humidity. I bought a wall mount humidity meter at a greenhouse supply. The scientific sling hygrometer is not necessary. You want a measured humidity of 40=50 percent. More than that is overkill. Distilled water or bottled drinking water both work perfectly. Never, ever use tap water. The utilities guys drag bags of copper sulfate through the reservoirs to kill algae, and this induces streaked finishes unles you run the tap water through a distilling machine. I bought one at a flea market for fifty bucks and it paid for itself the first month I used it.

December 23, 2001, 12:08 AM
Wow. You are really into it.

Don't you need nitric acid to make your own rust blue formula? I think I have the original Neidner recipe in my notes... Something about degreased nails and nitric acid...

Nowdays with the terrorist BS going on, you can't cruise into the Depot and ask for 12M Nitric Acid... Do you have a friendly source for a liter or two?

What works better than Plinktons? The stuff is expensive but lasts several blue jobs at least... 2 rifles and some tools- I still have 1/2 bottle left. I'd be willing to try something if better results could be had. I'm definitely getting that .0025 brush...

A good rust blue is tops for me- nothing else quite does it.

Can you pass on any secrets or tips we missed?

John Lawson
December 23, 2001, 12:19 PM
Nitric and hydrochloric (aqua regia). It is extremely dangerous to use, but worth the purchase of long neoprene gloves. The nails are hard to come by; I'm still using a supply I bought in the 60's.
A month ago, I bought a supply of the acids from a chemical supply house in Oregon. They ship by FedEx. No problem if you include your FFL copy with the order.
Neidner's formula works for rifles like the Remingtons, but I have my own formula developed over the last 50+ years that would be useless to you because they only work with my specific working conditions and on the specific steels I work with.
You will have to do some work on a buffer head to enable you to use the wire brush. It has to turn very slowly and you can't apply much inward pressure.
Slow rust blue is not for most gunsmiths. Some examples I have seen from well known shops are very poor examples of SRB. If you learn to use the hot water blues...that is, if you lose the instruction sheet and learn to use it by experimenting for a few years...you will obtain results identical to slow rust blue. In my opinion, some of those famous gunsmiths who listed the formlulas were carefully keeping their trade secrets; especially
So, here's the secret you asked for: Use iron pellets from the chemical supply house or look up some very old iron nails. Note that none of the formulas tells you how long to let the iron dissolve. This is the secret to success. You have to dissolve all of the iron to make a workable solution, and that may take a couple of days. You have to leave the crock outdoors, covered. If the night air is damp, you will run into trouble; the solution is best made in the summertime. If you can't wait, insulate the bottom, sides and top of the crock with styrofoam. You don't want water condensing in the acid. You know what that will do.
There you have it. Never say I didn't give you the secret you asked for.

December 25, 2001, 02:34 AM
I've been interested in this topic for a while now, but really haven't got much information about it yet. Can anyone provide some information or a link about every little step of the process form beginning to end? Can I make my own chemicals?

John Lawson
December 25, 2001, 10:02 AM
Well, I thought that's what we'd been talking about.
The Book "Firearm Blueing and Browning" by Angier, available from Brownells is quite informative, but aside from his peripheral description, the only full description available is in an article I wrote in Gunsport magazine more than 30 years ago. Maybe some reader has a copy they will reproduce for you; I gave mine away years ago.
The way you get proficient with this process is to experiment with it and to practice on different types of steel. If you aren't willing to do that, get a hot tank and just dunk the guns, being satisfied with the dead black color.

4V50 Gary
December 26, 2001, 03:20 PM
Depending on the humidity in your area, you may not even need a box. I tried one with a damp rag suspended over a light bulb and it rusted too fast. Scaly ugly rust. I used steel wool to remove the rust and restarted the process without the benefit of a damp rag. Just hung it up in the garage. Since you're in the Red River area, it may be different than coastal California.

Experiment first. BTW, prep work is key and the other thing to remember is different steels react different to the bluing solution.

December 26, 2001, 09:11 PM
Thanks everyone for the advice. I have found a couple more writings on the net and read what info is in all of the GS Kinks. I have a couple of pull-off Turk '38 barrels I will "practice on" (without a humidity box) with Pilkington's from Brownells (http://www.brownells.com) before trying on any of my barreled receivers. 50$ for the solution and a carding wheel should give me some idea if I have what it takes to blue my own creations, or should send them to someone who can do them justice. Just the thought of building a rifle from start to finish...