I came a cross a post (but couldn’t find it again) asking about “Blackening” brass/Bullets. One of my other interests is blacksmithing / metalsmithing. Some time back I learned that Copper/Brass Bronze and Silver can all be turned Black using “liver of sulfur” dissolved in warm (120-140 Deg F) water. Metal must be de-greased / cleaned first, then dipped into solution and either repeated until color is satisfactory or held in solution until its is. Another method would be to brush it on, the key being don’t handle it with bare hands. The chemicals are hard on the skin, in fact can seriously burn if left on the skin, so using rubber gloves and eye protection is required. The Stuff is a mixture of Potassium Sulfites/sulfates… Available through companies like Rio Grande, and here in the USA Hobby Lobby even sells a small kit with two oz in an applicator for “Patina” of jewelry. I’ve used it to “Antique” copper, brass, and bronze. Never tried it on Bullets or brass cases, but should work the same. Hope this helps answer the question for someone
Some of the blackened cases in the US are referred by the producers as “Black Nickel” finish. I have run across this at the Shot Show and have some examples, but I don’t know what the process actually is.
The internet describes it as:
Black Nickel is electrolytic nickel plating with a secondary treatment to turn the surface black . This plating will provide corrosion resistance and maintain electrical conductivity while reducing reflectivity on the surface.
Birchwood-Casey Brass Black is available in most gun shops and works OK to darken brass. Brush on, leave and wash off. Polish with steel wool. Good for small jobs.
I forgot about Brass black, and yes it works. The Black nickel has been around for awhile Lew. But its expensive.
You can find metal darkeners in the coin collecting world as well, sometimes used to hep correct the patina of a coin which has been cleaned. Deller’s Darkener is one that I remember, and it worked to help turn bright shiny copper pennies to a darker copper patina.