lye and boric acid for blueing?

[jigger]

Years ago a gunsmith friend gave me a recipe for a mixture to blue one of my old favorite shotguns. It consisted of lye and I think it was boric acid.
I used it and ended up with a beautiful finish .... I have another patient but my poor old brain just can't come up with the percentages..or even if boric acid was the second ingredient. My friend has since passed on so having never written this down I'm lost..
Has anyone ever used this particular mix?

[Jim Watson]

Haven't heard of boric acid in a bluing mix, nor is it shown in Dunlap's book. There is some mention in it in the old Angier book but all I have of that is a google on the table of contents.

Common home bluing salts are sodium hydroxide (lye) and nitrate fertilizer; either ammonium nitrate (OUTDOOR USE ONLY) or sodium nitrate.

Do not use any bluing product containing lye on a double shotgun or one you know or suspect to have a soldered vent rib. Hot lye solution will dissolve the solder and the gun will fall apart.

[FALPhil]

Yeah, if you use the ammonium nitrate solution, the boil off is tremendous and will eat your lungs.