Weird colored brass

[Timothy]

I’m sure I sound like the Village Idiot, but here goes.
At Christmas time I took my grandson to the club to shoot my P32. We shot 100 rounds and he found all but six brass in the light snow and slop. I laid them out to dry and tonight (two months later) I tumbled them a couple hours and when I took them out, two-thirds of them were each partially discolored. The discoloration was an iridescent purple, that rainbow effect you get when you put a torch to copper. The location of the color was not consistent from brass to brass and like I said a third of them were perfectly shiny. It will not rub off with a cloth. A mild abrasive does remove it. I’m not anal about the discoloration. Just wondered exactly what happened since I never had it occur before no matter how crudy the brass was.
Can anyone enlighten me?

 

[mete]

Sounds like there was something on the brass such as lubricant. Brass (actually the copper in it) forms a sulphide sometimes an oxide , or copper carbonate . So you might get black or brown or green or combinations of these.

 

[griz]

I haven't seen that. The worst I get is a tarnish when I find the ones I missed after a week or two.

Once a group of us was sorting brass after a match. Most of us put various marks over the headstamp so we can tell who's is who's. One guy remarked that there was a patina on my brass. Although I tumble them I'm not hung up on shiney brass. Wasn't sure how he meant it.

 

[HankL]

Tim, Any salt or snowmelt stuff on the ground at your range?
Just a thought.

 

[Frohickey]

ne guy remarked that there was a patina on my brass. Although I tumble them I'm not hung up on shiney brass. Wasn't sure how he meant it.

You should have asked him if he wanted to buy them from you. Tell him you'll give him a good deal on it.

 

[Blackcloud6]

Was this discoloration on the neck and/or sholder? If so, the brass may have been annealed.