Homemade Blueing Salts

[edwin41]

maby this is an idea , get a steel pan or something and fill this up with brass chips , like the chips youll get from milling down some
brass casings or so and put your object in the pan . ofcourse all covered with these chips. heat up the pan over a stove or so.
these chips will spread the heat evenly over the entire object . look from time to time if you like the coloring and if you do , quensh it in water or some light oil. ive tried this and really liked the results.
no chemicals involved , and you dont overheat the object .

[oldred]

Again just as with Nitre blue, and even more so with this method, heat treated steels could be adversely affected or even severely weakened. Casehardened soft steels probably would not be harmed unless the heat was allowed to go too high but it could seriously affect through hardened alloy steels like 4140HT and 4150HT, using this method for small non-stressed parts may work great but on something like a revolver cylinder for instance might be dangerous. Heating a heat treated and tempered alloy part to the point that the steel changes to a blue color could wreak havoc with the structural strength!

[gunoholic]

the ammonium nitrate/lye hot black works really well but i like the slow rust blue, the one i use is from roy dunlaps book:
2.5 oz nitric acid
2 oz hydrochloric acid
1 oz wire nails
30 oz distilled water
i made only 1/5th of this because 200mls will last me ages.
outdoors with all the safety gear on mix the two acids, then add the nails, and if you have neighbors only do this on a windy day or you may get a visit from the law, this gives off nasty red fumes, and if what i've read about other nitrating reactions it is highly toxic.
after it stops reacting add the acid to the water and its ready to use.
the link that oldred posted (#37) should work for the rest of the process

[gunoholic]

phosphoric acid works well for removing blue and rust, you'll find it at the hardware or automotive store in the paint section for rust removal, or a hydroponics store as ph down.
and if you coating a "black gun" get some mat black engine enamel, after you oven bake it its real hard and solvent resistant.