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I've been using cold blue for years, never that satisfied with the results.

In a recent project, I used Brownell's Oxpho Blue Cream, which they advertise as the toughest cold blue going. It goes on great, but the color just isn't as black as hot blue.

Applying Brownell's Dicropan T4 Touchup Cream after the Oxpho Blue adds the black color and the job looks like hot blue.

IMHO, that's the best one-two punch available in cold blue.

Give this combo a try as see for yourself.

DF

On hot metal Oxpho-Blue does really well in a single step.

I pour boiling water on the metal to start and the blue works much better.

I've done the T4 over Oxpho and sometimes it does help, depending on the particular steel. Sometimes Oxpho blends in better, sometimes T4, sometimes a combination. And sometimes Birchwood-Casey's. There's 44-40 on the bench which comes out exceptionally dark but I've had serious after-rust problems on test pieces.

Technique seems to matter a lot with Oxpho.

Thanks for the tip on heating the steel.

DF

Several years ago I had several cold blue products that I'd tried with each one being very unsatisfactory. Had a beater sporterized small ring mauser rifle that I decided to cold blue. By then I'd found both Blue Wonder and Oxpho Blue to work pretty good, but decided to mix the poorly performing cold blue products together and try it.

Much to my surprise, the mixture produced a rather darn nice blue job that was fairly comparable to a hot dip blue job. Next day, I mixed another batch and took another sporterized military rifle and tried it on it. LOL, this time my mixture worked rather poorly. So bad, I prepped the metal again and used the Oxpho on it with decent results.

As I recall, I combined Birchwood Casey Permablue, G66 Blue Cr�me, and cannot remember the third one.

If you are having after rust problems, here's a trick I learned that takes care of the problem. After you are satisfied with the blue, neutralize it by running under a strong stream of hot water. After the water evaporates and while the metal is still hot, give it a liberal application of Birchwood Casey Sheath (which is now called Barricade)and let the metal set for 24-48 hours before wiping off with a paper towel. Apply paste wax of your choice and polish with a micro-fiber cloth.

I neutralize with a baking soda solution with a drop of dish washing soap to break surface tension. Not always practical for a touch-up though and always a nuisance. All the cold blues are acid based. Mostly it seems the acid "wears out" during the bluing process. I suspect 44-40 has a little more acid than necessary and the excess caused the after-rust problem. Does give a quick, black blue on difficult steel though.

44-40 is selnic acid and can give good results. Works better with steel warmed up a bit. Carding helps smooth out the results.

That is a great idea of heating up the steel first. I did an old 22 mag, H&R semi-auto some years ago with cold blue. Well, with the cheapo Caseys brand, but it looks more like a case harden job gone bad then anything! But ended up having it coated. Guess doing it right, and using something a bit better then what you pick up at Wal-Mart helps out too.

I've had great results with Oxpho Blue cream. I usually coat and card several times and if its a hot day I'll put the parts in a plastic bag, spray them down with Rem Oil and let them bake in the sun for the entire day. I think heat really helps.

Selenic or selenous acid is common to all cold blues. Other chemicals and the proportions distinguish the products. Seems to me that's why some work better than others depending on the composition of the steel. An acid is added to give the solution "bite," often nitric, in some proportion. Oxpho Blue uses phosphoric acid instead which deposits iron phosphate for some rust resistance. But you get the effect of removing the first coat if you apply a sloppy wet second coat. The instructions say apply subsequent coats with a lightly moistened pad and they mean it. I suspect 44/40 is a little heavy on the nitric acid and that's why it's so aggressive.

I've had better luck getting a darker color by oiling and letting set overnight after the last application before carding. The coating seems to harden some.

No nitric in 44-40 selenious acid, cupric sulfate, amidosulfonic acid polyoxyethylene stearly ether.
The amidosulfonic is the cleaner.
The cupric sulfate forms iron sulfate on contact with iron.

That seems to be unique though why not. It'll passivate steel (and clean your toilet). I believe the copper sulfate (in all the formulas) deposits copper on the steel and the selenium acid combines to darken it, but then I'm not a chemist. A saturated solution of copper sulfate with a drop or two of sulfuric acid applied to steel makes an excellent copper surface on which to scribe.

one I use that not many folks seem to try is DicropanIM
it realy works well on steel that is warm and pickled just a bit. then applied with de-oiled 0000 steel wool

it generally is a bit more of a Blue color verses many of the typical cold blues but it's really tough

every now and then you'll find a steel it just doesn't seem to take well on and then it's time for Oxpho or T4


it will simply puddle on the surface if it's not taking

if you try it get the instructions from Brownells on how they use it as a replacement for rust bluing. it will guide you.

Been using Hoppe's cold gun blue. It is mostly selenious acid. I find he results
to be just so - so and have never really been satisfied with it.

going to resurrect this conversation....just bought a very nice pre-64 94...other than someone engraved their initials into the action. lines are fairly deep, no rust apparent. I want to just color them in with blue/black to subdue the look. What should I use?

Brownell's Ortho Blue works well,but degrease good and then preheat the metal before applying.

saddlesore
how "warm" should you pre-heat to and what heat source do you use?
rookieatbest

I have used a hair dryer or a heat gun. About 150 degrees F is the hottest a human hand can hold. So I"d say about 125 degrees or so. I usually heat it so it is pretty warm to the touch. Don' t let compound dry,but give it time to work.Then wipe dry,let sit over night and buff with cotton cloth for a bluer color or 0000 steel wool for deep black according to instructions repeat to get deepercolor

will it wipe off the flats were original bluiing is still in good shape? Im just looking to fill the "scratches"