Cold blue is just a cold or room temperature chemical such as Brownells 44/40 or Oxpho blue. Used for touch up only, it doesn't wear very well. Blues the surface of the steel.

Hot salt bluing is performed with a salt bath tank heated to around 285-295 deg. F. with a hot cleaner tank for degreasing, a hot water rinse, cold water rinse. Hot salt bluing will wear much better than cold blue because the blue goes deeper in to the metal.

 

First of all, let me thank you for answering all my finish questions. You've been very helpful.

Your description of hot bluing makes it sound pretty complex. Am I misunderstanding? If I'm not, it would seem that there are other finishes that are no more complicated to apply, but wear (if not look) much better.

Finally, are there any good finishes that produce a dark blue or black color that are easier to apply than hot blue?

Thanks again.

 

Our TactiKote polymer finish is flat or semigloss black and we do many handguns, rifles knife blades and shotguns in this finish with excellent results.

 

DICROPAN "IM" http://www.brownells.com/aspx/ns/store/ ... N+%22IM%22
click on instructions link will give you very detailed directions, Like the add said it's time consuming and a little labor intensive but much less equipment is involved pretty suited for the occasional gun. I have seen several done with this and results are pretty good. A side note though, according to the guy who uses this stuff it will pretty much rust everything else in the room, guess you need alot of ventilation.

 

There is another alternative "IN-BETWEEN" hot and cold blue, called rust blueing.

This process uses boiling water. One prepares the metal by polishing and degreasing. Then, a mild acid is applied with a cotton swap. The metal parts are allowed "to rust" for a day or so, The the part is immersed in boiling water to set the rust. After drying, the rust is lightly removed with fine steel wool -- and a blue steel surface is underneath. Usually 2 to 4 coats are processed in this manner.

This methodology is often used on SxS and O/U shotguns, since the solder joints on the barrel preclude hot blueing.

I've successfully refinished several guns in this manner, and it is not difficult to do. Supplies available from Brownells.

 

Any sort of heated bluing process, overtime, will literally rust the nails right out of the wall of the room you have it in. Heated bluing is in reality controlled rust.