Slow Rust Bluing

RogerN wrote:

I knew a gent who ran a place making new old rifles. Things like flintlocks, matchlocks and such. All made in house and done using mostly period correct methods (his barrels were hammer formed BUT drilled/rifled with modern tools).

He did both slow rust bluing and browning. The slow rust method he used had three tanks the size of the finished metalwork. One was for boiling in PURE water. No tap/well water. He used distilled in his. Another was the degreasing tank. This also was boiling with lye solution. The last was the acid fuming "tank" This was something he built out of lexan. The corners were hot wire bent and sealed with the top secured with a few cam lock closures.

The basic procedure was to polish the steel as perfect as you could, Then boil it in the lye solution for 5 minutes. This removes ALL oils/dirt/crud. Remove from tank without touching the clean steel with anything that may have oil/dirt on it. Then into a boiling tank of PURE water for 2-3 minutes. Remove it from this tank and hang it someplace to cool to room temp. Once cool it goes into the fuming box. In there you add some 70% nitric acid in a container that is open to allow fumes out. His used some PVC cut in half and bonded to the bottom as a container. You stick the item in there and let the acid fumes go after it. (with a finished barrel you take some grease and grease the bore and plug the ends with corks, one solid and the other with a chunk of tubing in it to allow air in/out of the bore during the boiling cycles, plug the tube during fuming) Let it set in the box until rust forms. Remove from the box and boil in CLEAN PURE water until the rust turns to black oxide. Remove from the water and card off the excess rust with OOOO CLEAN steel wool. Wipe clean and repeat until you get the color you want. 5-7 cycles will usually put you in the ballpark. After the last cycle you need to remove the plugs, clean out the grease and boil the finished item in a reduced lye solution to remove any left over grease and any remaining acid. Net you oil the parts with a good coat of boiled linseed oil or engine oil. Keep checking to make sure that it has completely stopped rusting. It's easy to miss just a small spot while carding off the rust.

Enjoy the finished item. The fume method has two BIG advantages over other ways. One is less chance of touching the steel and leaving marks in the finish, the other is that you get a very smooth, even coating with no runs, drips or streaks that usually happen with the brush on methods.

"RogerN" wrote in news:PPGdnTzbfufEpNjMnZ2dnUVZ snipped-for-privacy@earthlink.com:

I've used a rust blueing solution that Brownells sells, and it works very nicely. It takes a couple of treatments to get a really deep blue/black. I think I used steel wool between treatments, but you need to degrease the steel wool. The stuff I used is "PILKINGTON CLASSIC AMERICAN RUST BLUE" and is NOT cheap, but it works fine. I used it on a machine tool part that was originally blued, but the replacement I got from Clausing was "in the white". Brownells sells their own flavor of solution, and it is much less expensive, but I haven't tried it.

Red rust is Fe2O3, and is both porous, and the molecules are large enough that they flake off. The black that you get from converting red rust is FeO, non-porous, and a much closer match in terms of molecule size, so it seals the steel and doesn't flake off. Think of it as anodizing for steel.

Doug White