There is a very interesting thread going on right now about using steam for rust bluing.

My questions are these.

1. What is the difference in the chemistry and the theory between what they call "caustic" bluing and rust bluing. I understand that rust bluing makes some sort of dark colored oxide on the steel. Is that rust. Or what is it. And what does caustic bluing make. Is it a dye?

2. I wonder why some very famous makers like David Miller and D'arcy Echols recommend and use caustic bluing on their very expensive rifles. Is it superior to rust bluing?

Both Rust bluing and caustic bluing are oxidizing the steel; rust bluing is a red Ferrous oxide conversion to ferric oxide, which is black. It is not rust; you have converted the rust into another oxide, which is black. Caustic bluing is basically boiling the metal in sodium hydroxide and ammonium nitrate, lye and fertilizer. Easy and quick to do, it also will burn your skin as it is very caustic and operates at 290 degrees, and is hard to dispose after you are done. Rust bluing takes longer but results in a classic, somewhat more matte (depending on how long you let it rust. Hot bluing is used only because it is fast; not because because it is better. Caustic bluing is not really suitable for home or small shop use. Cheaper and faster, yes; better; no.

Do a search for "bluing ware" [sic] in this forum category, I cannot cut & paste on my iPad.

Even if some tests show that hot bluing might be slightly more abrasion resistant than rust bluing (not more corrosion resistant), it is a moot point if the home guy is doing it; hot bluing is not practical for home or small shop use; and I have done it. Rust bluing is simply easier to do with less investment and practically no toxic or hazardous risk to you. Caustic blue will burn and kill everything it touches. And it is hard to get rid of when you are done with your one or 2 bluing projects a year. For big shops, fine.

seems like every bluing tank I have seen photos of was set up to hold gallons of solution. could a small tank, just big enough to hold a barrel, or small pan just big enough to hold an action, work?

I would think the used solutions could be poured into a glass bottle and dropped off at the local hazardous waste place for processing just like the larger businesses do.

Does caustic blue eat through good protective rubber gloves?

For the one or two projects a year that require bluing, I've come to the conclusion (the hard way) that sending it out to a pro is money well spent.

Lindy2- Yes a small tank or pan works the same as a larger one. The reason larger tanks are preferred is commercial shops do more than one gun at a time. When I worked in a bluing shop we wouldn't heat up the tank for less than 6 guns and did as many as a dozen in one bluing session.
Also, caustic blue will not eat through good rubber gloves.

I caustic blued for years in a 4-5 gal tank. It is a MESS. you need a take to strip out all the oil. You need the blueing tank then a tank to replace the oil.

As stated 290-310deg so you need a stand to hold the tanks the burners. There is so much caustic chemical it won't dissolve until you get in the high 200deg. You control your temp by water content not the burner.

The salts tend to climb out of the tank as the crystalize. Eat through most it touches. It was a mess, I made a room in my garage just for the tanks. Rubber gloves, rubber apron, face shield or very least eye wear.

You can get into rust blueing for a few $$. Brownell will sell you the a full caustic system for around $2000.

Looking back it was a great day I sold my system. Do a little research on the net and youtube. It is a mess.

I always thought a good rust blue was harder to remove. Caustic hit it with a touch of acid and it is gone.

I don't intend to do it myself. Just trying to learn something about it.

Lindy go to this link you can see the equipment. http://www.brownells.com/gunsm...em-kit-prod1113.aspx

I used 4 tanks 3 were heated. Cleaner, salts, boil water bath and oil tank. There are some articles attached. Even with small tanks I would do it in batches of several guns. Takes a while to heat everything up. If you can imagine if your salts are getting to hot you need to add water to dilute them and reduce the temp. So you are adding water to a tank of liquid at 300+ degs. Kind of like ice and a turkey fryer.

Unless you had real clean tap water or rain water you were using bottled.

Ram is right; yes you can do salt bluing in small batches, I have done it in enamel pots, but it is not as easy as rust bluing, now that we know how to steam the metal instead of boiling. And as well as messy, it is dangerous. And as he said, the temperature is not regulated by flame, but by the salt concentration to water ratio. Get it wrong and your steel comes out red. Not kidding.

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steel comes out red.

Been too many years. Seems like the old Springfields had to go into the tank at around 290-295 the you left them there until it was about 310 or so to keep them from being a plumb color.

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Get it wrong and your steel comes out red. Not kidding.

When I was young and foolish one year I decided to give my father a present of having his Winchester Model 12 shotgun reblued by a local gunsmith. It had been used quite a bit and needed rebluing. I think I paid something like $50 back then.

My Dad and I always wondered why it came out red, and now I know.

Yes, iron and hard steel comes out reddish unless you jump through hoops; look at some Ruger 77s. Early 03s, and case hardened receivers are prone to it, as is old iron shotgun frames.

The old Brownell Gunsmith Kinks had several chapters on how to do those HOOPS

You could get around or cure MOST of the reds. Some would come over time or in bright sun it was still there to a limited extent.

Don't even want to think about the caustic and the old solder on double ribs.

Stick to rust bluing.

dear goodness, i am glad i sold my hot blue tanks... it is actually easy to do .. once you understand it, and realize that ANY slip is 300 deg lye on your skin, and any breath of the steam is perm lung damage...

one thing i have been playing with, for small batch rust bluing -- is to boil "plum brown" ...

i'll pick some up this month and try steaming it...

why plum brown? well, dang, its easy, and it doesn't stink like cold blue

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Originally posted by lindy2:


My Dad and I always wondered why it came out red, and now I know.

I'd bet it was nickel steel. Needed to let them stay in the tank until 305-310, like ramrod340 said. Even then, they might stay black or turn plum after a period of time.

I've been hot bluing since 1992. I am still hot bluing but only about once a year now. I have pretty large tanks so I try to do as many projects as I can, starting around 6:00 AM. Sometimes I don't finish until 7:00 or 8:00 PM. At the end of the day I am worn out. I have small tanks for handguns, they are not that hard to operate.

If you prefer the quite elegance of slow rust blue like me you can duplicate the look by careful hand polishing and a few other techniques.

Be careful who you trust your gun to for bluing. The stories of butchery with a buffing wheel, botched chemistry, scratched or damaged parts and lost parts are rampant.

For me the biggest headache with caustic bluing is "creep". It is hydroscopic and will form solid crystals and creep out of the tank and all over everything. There are measures to combat it but I don't think you can eliminate it.

You also need a separate room or shed to keep fumes out of your shop otherwise it will rust everything in sight.

I am considering switching to slow rust blue in the future. I am part retired now and beginning to down size a lot operations.

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Originally posted by yellowdog1:

quote:

Originally posted by lindy2:


My Dad and I always wondered why it came out red, and now I know.

I'd bet it was nickel steel. Needed to let them stay in the tank until 305-310, like ramrod340 said. Even then, they might stay black or turn plum after a period of time.

You would win that bet. It was a very early nickel steel one. I think the date of manufacture was around 1912 or 1913.

A 1912 or 13 Springfield would be a low number (below 800k) single heat treated low carbon steel; not nickel steel. The early ones were case hardened in leather, which means the surface is full of carbon, which is why they turn red in bluing. NS springfields came out in 1927. Nickel steel 03s are very soft, whereas the case hardened ones are very hard, both the single and the double heat treated ones.

dpcd-Yes, you are right about the Springfields, but lindy2 was talking about a (Winchester) model 12 shotgun made in 1912 or 1913. Those years were nickel steel.

oops

I used to rust blue and I still have my cabinet if needed, but its such a mess that I just send them out now...D'Arcy does a hot blue and its beautiful. Seems to wear as good as any and it looks like rust blue..

Rust blue done on polished metal last forever, just take a look at such rifles as the old mod. 21 Brno's, after 75 or a 100 years and the blue is beautiful even with hard use.

I personally like rust blued guns as long as they are not bead blasted first..in fact I don't like bead blasted anything with the exception of SS firearms..those little pits are like pools of water and hold moisture IMO, and they create rust, even though the look is nice when new..

Several trips to the Selous, Alaska, So. Texas and Idaho mountain tops, to name a few turned me off on bead blasting chrome moly type metal...

Age is playing with my memory, but it seems I recall threads on this board from many moons ago that talked about rust bluing being quite fragile and not lasting very long.

And I seem to recall threads that talked about factories of old not using rust blue like everybody thinks they did, but rather using something else like a charcoal blue or some other kind of bluing.

I remember way way back when I was a youngster and my Dad told me I was going deer hunting with him that year and presented me with a used but nice condition Winchester Model 94 30-30. I have that gun today, and I marvel not only at how the bluing has lasted, but also its color. It doesn't look black like a lot of "bluing" one sees. It actually looks blue!

Rust bluing is not fragile; it is the charcoal or heat blue that wears off if you touch it. Completely different process.