Thread: Cold Bluing.

Originally Posted by No.3

Meticulous surface prep - any areas that are different, corroded, old blue etc will take the cold blue in a different way. There are different types of cold blue chemicals and some will work where others dont... Worth keeping in the back of the mind on your 15th attempt at coating a stubborn spot.

+1 on surface prep, it will determine the outcome primarily.

Test process on a piece of scrap steel then you know what you're in for.
Clean with solvents and or wire brush, steel wool etc until clean, then begin the meticulous part.
Sand with wet+dry 600-1200 grit to remove any deep staining on the metal, then begin polishing.
If you have access to one, use a metal polisher wheel. Even the cheap drill chuck mounted setups. Buff until shiny, a mirror finish if possible. The smoother and shinier the metal surface, the better the bluing will look. Polishing will only be difficult in some nooks and crannies, and these areas will end up with a different bluing appearance than the more shiny areas though, so I guess you have to decide how far you are going.
I did an old single shot .22 for fun, and the whole process took me most of a day, but I was surprised with the result considering the fairly low cost.