Blueing question.

[1 Old Gunner]

I’m at the point where there is no saving the original bluing on my rolling block. I’m going to take everything down to the white a give the exterior parts a nice shine. Somewhere between matt and mirror finish.
My question is should I use a cold blue or rust blue. I’m equally capable of doing either.

Thanks.

[marlinman93]

If you're capable of doing good rust bluing that's what I'd do.
There's only one cold bluing solution I ever use and had great results with, and that's Brownell's Oxpho Blue. It gives very close results to rust bluing if done properly, and has proven to be very durable for my barrels.
I usually use Mark Lee rust bluing solution and like his Express Bluing a lot. It avoids all the lengthy sweat box time, and can be finished with 5-6 coats in one day.
I just did this Hepburn barrel recently using Oxpho Bluing solution:

[wlw-19958]

Hi There,

My question is should I use a cold blue or rust blue. I’m equally capable of doing either.

I'm a purest and Rust Bluing is superior to Cold Bluing. Cold
Bluing isn't really bluing in the conventional sense. Bluing is
the formation of Iron(2) Oxide or Ferrous Oxide and Cold Bluing
is a deposit of copper sulfate or copper selenium on the surface
of the steel and generally are not as durable as conventional
Iron(2) Oxide blue. Cold bluing is easier to apply but to get
really good results, the surface needs to be properly prepared.
Cold bluing is more forgiving to contamination. Rust bluing
needs to have the surface properly prepared and is not forgiving
to contamination.

There are a couple of different ways of "rust bluing." The slow
way is to coat the surface with a oxidizing agent and putting the
parts into a warm humid environment (like a rusting cabinet).
The parts are removed after a layer of fine rust has developed,
carted and returned to the cabinet to rust some more. Often,
the parts have to be heated to turn the rust black (forcing the
rust to change from Ferric Oxide to Ferrous Oxide) between
rusting and carting sessions. It can take 5 to 20 applications to
achieve the desired results and it can take a day or more for
each application to form enough rust to cart. It depends on
the type of steel and what heat treatment it has received.

There is a "quick" version that uses a tank of boiling water to
accelerate the rusting process. The water has to be chemically
pure (tap water won't do) or it will affect the rusting process
and the metal surface has to remain free of contamination during
the process or the metal will not form rust. It is called the "quick"
way because the time from application of the rusting solution to
the carting and re-application can be as quick as 15 to 30 minutes.
So, a gun can be blued in a single day (instead of weeks).

Either rust bluing system requires the metal to be absolutely
clean and to stay that way throughout the whole rusting process.
This makes it a very labor intensive system and why the cold bluing
process is so popular.

Whichever way you go, I hope get the results you desire.

Cheers!
Webb

[1 Old Gunner]

I’ve noticed that there are multiple types of metals used in the construction the rifle. I know they will react differently if cold blued. How do dissimilar metals react to rust bluing?

[marlinman93]

I’ve noticed that there are multiple types of metals used in the construction the rifle. I know they will react differently if cold blued. How do dissimilar metals react to rust bluing?

Rust bluing works well on almost any ferrous metal, but the softer it is, the better it works. And I discovered that too high a surface polish finish will result in rust bluing not taking as well as a lower finish.
The first barrel I polished many decades ago I took to a local gunsmith who did wonderful work. I polished it to a finish that looked almost like chrome using 500 grit wet/dry paper. He took one look at it and chuckled. He told me it was gorgeous, but he was going to have to knock it down with a Scotchbrite pad in order to rust blue it. He told me anything more than 320 grit is a waste of my time, and even 320 that's well used can over polish the metal.
He also color cased the Ballard receiver it went on, and said it was great as is since color case comes out better the nicer the finish is.

[wlw-19958]

Hi There,

marlinman93 is correct. All other things being equal, polish will
affect how well the surface will take to rusting. Hardened high
polished steel will have the most trouble taking rust bluing. The
other way to knock down a highly polished surface is to "pickle"
the part. This means to immerse the part in a weak acid to lightly
etch the surface. Nitric acid was the pickle of choice long ago.
Just don't use a solution that is too concentrated. Error on the side
of a really weak solution. If too weak, just leave it in a little longer.
One just wants to knock the "shine" off. When rust blued afterwards,
It will leave the part looking like the classic blue of the old military
firearms made in the 19th Century (and early 20th).

Just for comparison, Highly polished hardened steel may not take a
hot caustic blue (depending on the steel used). So, the pickling
step may be needed even then.

Cheers!
Webb