Yes I know there are products dedicated to blackening brass parts but I had none on hand but I do have an awful lot of gun bluing chems on hand so I thought I would give it a go. None of the bluing companies will tell you the exact recipe and proportions of chems used and because all of them said their products would only work on steel I tried a little test on other metals. They were correct to a point. I was however impressed with their ability to blacken brass. (some more than others) Restoring some really old guns requires brass blackeing and while there are products one can buy to do the task, after seeing how well some of the gun blues worked on brass I dont feel the need to buy a separate product for the job. Clearly these products all have a different recipe and varying amounts of sulfides and acids and oxides as they all performed diffeently on steel and brass.
Here is the line up of bluing agents I have on hand including aluminum black
I used a piece of brass bar stock I had in the shop that I use in knife making projects. I cleaned and buffed the test area and then applied all 7 products. Some were quite harsh to the brass and some not so much. Some really darkened the brass and some not so much but rest assured all of them did blacken brass.
Then I used steel wool to abrade off the blackening. It took some effort but all gave up the coloring but then brass is a very soft metal and steel wool is much harder so it was no surprise. I was pretty aggressive in abrading the brass and was impressed with how well they held up considering they are not meant as brass blackening products. Then I went a little nuts since I was looking for more brass to sample. These were done with Oxpho-blue as I found it the most effective on brass (the most black). The G96 was the most caustic and damaging to the finish of Brass. It deeply etched/pitted/damaged the surface of the sample bar.
If you find yourself in need of blackeing brass and dont have any brass black on hand, you can substitute gun bluing.
Could the above method be used on Russian Steel cases after the poly finish has been tumbled off? This seems like a perfect way to protect steel case ammo from rusting if it's in fact safe to shoot. Was thinking of trying some oxpho blue on a steel cased 7.62x39 and 7.62x54R jut to see what happens.
The chance that the bluing compound would get in and contaminate the primer or powder would be rather high I think.
This would be done before the powder / primers put in, on the raw cases. I actually tried this method last night but on brass. I wasn't impressed as using 000 steel wool to buff it out just took the finish off the brass. I haven't tried it on steel case yet. I don't have any that I've tumbled raw. I suspect it will blue the cases better than brass, I just don't know if there's any ill side effects if you were to load these up afterwards and shoot them.