Hot or Cold

Polar Bear

They call me Mr Sunshine
Verified Military
Aug 14, 2006
I have a Browning 12 Ga that needs re-bluing. Have never heard of Hot bluing before today what is it exactly?
Sounds like a science project

Hot vs. cold bluing
Bluing may be applied, for example, by immersing the steel parts of the gun to be blued in a solution of potassium nitrate, sodium nitrate, and water heated to the boiling point. Similarly, stainless steel parts of the gun to be blued are immersed in a mixture of nitrates and chromates, similarly heated. Either of these two methods is called hot bluing. There are many other methods of hot bluing. Hot bluing is among the most effective forms of bluing, providing the most permanent degree of rust-resistance and cosmetic protection of exposed gun metal.

There are also methods of cold bluing, which do not require heated solutions. Commercial products are widely sold in small bottles for cold bluing firearms, and these products are primarily used by individual gun owners for implementing small touch-ups to a gun's finish, to prevent a small scratch from becoming a major source of rust on a gun over time. At least one of the cold bluing solutions contains selenium dioxide, to accomplish the bluing. Cold bluing is not particularly resistant to holster wear, nor does it provide a large degree of rust resistance. It does, however, often provide a very good cosmetic touch-up of a gun's finish when applied and additionally oiled on a regular basis.

Cold bluing is often applied by first cleaning the steel area to be blued with alcohol, allowing the area to air-dry, touching a cotton swab in the cold bluing solution, applying one or more applications of the cold bluing compound to the steel being blued to match the rest of the hot blued finish, allowing the area to dry completely, and then using a good grade of gun oil to rub onto the cold blued areas, overlapping with the original hot blued areas. Provided regular oiling and rubbing is done, this method will provide adequate protection against rust for many gun owners.

Hot bluing and cold bluing kits and solutions are also sold commercially, for use by gun hobbyists.

Large-scale industrial bluing is also performed using a bluing furnace. This is an alternative method for creating the magnetite (black oxide) coating. In place of using a hot bath (although at a lower temperature) chemically-induced method, it is possible through controlling the temperature to heat steel precisely such as to cause the formation of black oxide (magnetite) selectively over the red oxide. It, too, must be additionally oiled to provide any significant rust resistance.
hot blue is always better, but you have to make sure there is no alloy parts on it that will be eaten away by the acid, a lot of Brownings have alloy parts

when you say it needs to be reblued,..why do you say that?
Why because the guy that had it before me let it sit in a closet and get surface rust. I cleaned it up and cold re blued it looks like shit. I don't know about the ally parts but my guess it has none. Belgian made 40 + years old
even 60 year old ones have alloy trigger guards, the pitting from rust won't take a good blue, you have to smooth it off, take it down to bare metal, so if you have not done that before, might be a good idea to have a gunsmith look at it.

The alloy parts usually look blacker, and the most common parts are the trigger guards, safety levers or buttons site bases, and these are generally not redone because they won't stand up to the cleaning or chemicals.

Take it to your armourer, I know when I was one I got about thirty such questions at a time, they usually have sense enough to tell you what to do.
If you want to see a similar process that is easier to understand, and also easier to do, you can brown your high carbon knives (not stainless) to a dull blue-black with vinegar, the process is called "browning" as opposed to blueing.

steel wool the knife so that the rust is mostly gone, and you have bare metal on the blade, you can also polish the blade if you like, it will be a smoother surface, dip the knife in either 60% or higher concentration alcohol and let it dry ( 100 proof vodka will work, but so will windex) This step gets all the oils and grease off the blade, make sure you don't touch the blade at this point or it will etch your fingerprints on it in rust, that is a bad thing (wear gloves if you are clumsy) Allow the blade to dry completely or hold it over a source of heat until the alcohol, vodka or windex dries (unnecessary if you are patient)

Using a smooth absorbent paper towel, soak the towel in vinegar (or 20% acetic acid if you can locate it) allow the excess liquid to run off and then closely wrap the towel around the blade, and then squeeze the towel to the blade surface so it touches all the contours. Then wrap a dry paper towel around it, and place the whole thing in a sealable plastic bag, get as much air out of the bag as you can, this creates an environment where rust forms in a lack of oxygen, so instead of the orange, fuzzy iron oxide rust, you get a smooth, hard, blackish rust that forms an oxidized layer on the steel.

WAIT three to six days to touch, move or open the bag, remove the paper, and you will see a hard black rust formed, lightly, with oiled steel wool (oooo) polish this layer until you get an even color, and then use it. What you will find is this layer does not rust easily, is not shiny or spotty and will last for a long time if kept reasonably cleaned and oiled.

This was a traditional metal finish long before blueing, and if you practice at it, you can also wrap thread or strips of the vinegar-soaked towels around it, and the edges will leave prints that looked like pattern steel or damascus.

I use this technique on knives I make for the kitchen and carrying, makes them look old and prevents rust well. Does take some practice, though.
I don't need to say that I really like the A5, I have had 2, might replace the link pin (B1111252 Link Pin 12M-12) if you feel any drag in the chambering cycle, it tends to wear too much, but they are great, nice smooth action and balance well, but I sold them to make way for more blackpowder stuff, such as my model 1900 Remington double,'s damascus, but I like the smell of blackpowder.
It is a Browning Auto 5 made before 1939

Something that old and an possible heirloom you will want done professionally.
When I was a teenager I used to work for a gunsmith by the name of Harry McGowen (McGowen Rifle Barrels). I used to do the stripping of bluing, polishing, and rebluing of barrels and recievers, anything that needed bluing. My suggestion to you is get it professionally done. Spend the money and get it done right the first time. You can find articles on the net about McGowens(spelled incorrectly on the net McGowan) work. He makes everything from barrels, stocks, competetion rifles to safari rifles. He doesn't have a web site but here is some info if you would like to contact him.
McGowen Rifle Barrels 5961 Spruce Ln., St.Anne Il. (815)-937-9816
Why because the guy that had it before me let it sit in a closet and get surface rust. I cleaned it up and cold re blued it looks like shit. I don't know about the ally parts but my guess it has none. Belgian made 40 + years old

Call GunnerJohn - he's the machinist/gunsmith/redneck/ex-cop/sociologist/gun store owner, and he actually knows something about this stuff.

He is humble though, he just calls himself an over-educated redneck.

Kinda like Shoe-shine Boy is really Underdog.


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