black annealing stains on copper

[yonky]

hi,i have just had some copper coil annealed to soften it,it has come back black,anyone got any idea how i can remive the black stains?

thanks ian

[Hickory]

What form is the copper in?

[yonky]

What form is the copper in?

its in coil form at the moment but will be pressed into 30 cal gas checks

[Sasquatch-1]

For brass I use a crockpot and citric acid. Cook the brass for about two hours and then into the tumbler with a little IOSSO brass cleaner. After you get it punch into gas checks this should work well.

[ph4570]

I have annealed Hornady GCs. They develop a flaky black surface. I put them in the ultrasonic cleaner with dish detergent and citric acid. They come out fine. I do not know if this is the same staining you are seeing But I would wager the same cleaning method would work.

[Dan Cash]

Why worry what they look like; gas checks are expendable.

[mold maker]

Until you bury them in a powder filled case, they look terrible. The next time you view them, their toast.