Yes, it's my understanding that all of the various rusting solutions are merely a means of accelerating the formation of ferric oxide, or common red rust. Then, if bluing (or blacking)is desired, they are put into boiling water or steam to convert the red rust into ferro ferric oxide, or black rust.
Over time, especially if a gun is not protected from atmospheric oxygen by gun oils or wax, this black rust will slowly turn back into ferric oxide which we call red rust, or more politely, patina. Of course, if this patina is blotchy or uneven, it would be necessary to strip and polish and completely redo the barrels. But we have all seen guns that get a very even and deep patina or fine grained rusting. It would be great if they could be boiled and carded to reconvert the patina back to the original blue/black? If that actually worked, would it be considered refinishing, or original finish?
