Quote Originally Posted by ignatz View Post
That sounds like a good recipe for gun parts, but if you boil a thin object like a straight razor blade you might be asking for trouble. If you do decide to do this, be absolutely sure that the blade is either supported or suspended in the water such that the blade does not contact the bottom of the pan you are heating the water in.
I have used a different bluing recipe (ammonium nitrite/sodium hydroxide) that calls for the blade to placed in the boiling salts - the salts raise the boiling temp of the water from 212F to around 285F. Although these temps are both well below the tempering temperature of razor steel I was still a bit nervous and suspended the razor by tightly fitting wire through the pivot hole so that the blade rested above the bottom of the pan, spine down.

I don't think it was really necessary from the tempering angle to do this, but it does stop patchiness and plummy brown colours caused by hot spots.

Regards,
Neil