Bob B257;
Good evening, I hope you all had a good Christmas in your part of New England and you're well.
My late friend who taught me rust bluing would also boil firearms on occasion to stop the rust. It's been at least a decade since I've done one, but going off of memory here's what I recall.
As he explained it to me, the boiling stops the oxidization process.
When we're rust bluing, we'd do successive repetitions of applying the rust causing agent - a combination of acids we got from an old gunsmithing book - then it's boiled for a few minutes in distilled water, then carded with oil free steel wool or a carding wheel as you've noted.
Depending on the metal, after usually 4 or sometimes 5 rust, boil, card/steel wool cycles, the bluing won't get any deeper.
The last boil then was with lye in the water, I can try to remember how much lye for how much water, but the reason was to help stop the oxidization completely.
Then we'd oil it.
I've boiled small parts in a tin to stop them from rusting further since and it worked.
Again it needs to be distilled water otherwise the scale from impurities can play hob with the finish.
Hopefully that made sense and was useful.
All the best and Happy New Year.
Dwayne
