can brass become stained?

[supergoat343]

I just started tumbling cases a week ago. I'm dry tumbling 9X18 MAK in cob medium. Some cases were very cruddy, almost black, from the range. After about 4-5 hours in the tumbler they come out very smooth and shiny, but still this dark brown/black. Is this as clean as they will ever get? Are they stained or can I do something to get them to looking like brass once more?

 

[ReloaderFred]

Brass tarnishes and that's what you're seeing. To remove the tarnish easily, buy some pure citric acid at the grocery store (normally where they keep the canning supplies). Boil some water and put about a tablespoon of citric acid in about a quart of water. Submerge the brass and let it set for about half an hour. Then rinse in hot water and dry. You can then tumble it and it will look new again.

Hope this helps.

Fred

 

[HOWARD J]

Pour some vinegar in a cup--add a teaspoon of salt.
Drop in cases & see if it helps---works on copper -- don't know about brass.

 

[bloominonion]

Pour some vinegar in a cup--add a teaspoon of salt.
Drop in cases & see if it helps---works on copper -- don't know about brass.

This will also work for gold too.

You can either just tumble the brass till the staining comes off, or do what Fred or Howard said. It looks a lot easier.

 

[brickeyee]

I'm dry tumbling 9X18 MAK in cob medium.

Try walnut, possibly with some light abrasive added like jeweler's rouge for the stubborn crud.

Treated walnut media is not that expensive to keep some around for really cruddy cases.

 

[clone]

I have noticed these as well when I pick up old 9mm/45acp range brass. I toss them in the scrap bin if they don't clean up in the tumbler within 3 or 4 hours. I have had most of them crack/split when shot, that's no good. My take is when they are "dark brown/black" they have been compromised by corrosion and should be tossed.

Stay safe folks.

 

[rcmodel]

Corn cob media will not remove stains.
It is best for highly polishing clean cases only.

Walnut media is more agressive, and will remove some staining, but sometimes not all of it.
However the final finish will not be as bright as with corncob.

Stains that the tumbler didn't get?
I generally just rub it off with 0000 steel wool and polish it again the next time.
That gets it all clear down to clean metal.

rc

 

[bloominonion]

Corn cob media will not remove stains.
It is best for highly polishing clean cases only.

Walnut media is more agressive, and will remove some staining, but sometimes not all of it.
However the final finish will not be as bright as with corncob.

Stains that the tumbler didn't get?
I generally just rub it off with 0000 steel wool and polish it again the next time.
That gets it all clear down to clean metal.

rc

Walnut media will get a BEAUTIFUL shine if you throw in a bit of car polish in each batch. I can get the brightest brass I have ever seen with walnut and Meguiars Ultimate compound, or use some turtle was polishing compound (the tub, throw just a bit in).

Pulls any tarnishing out and leaves them gorgeous.

 

[918v]

Dip the black brass in vinegar. It will take the black right off.

 

[FROGO207]

I pre-treat my tarnished brass with IOSSO case cleaning liquid. Then tumble as usual. This also works with powder stains also.

 

[amlevin]

Since I trim my .308 brass with a LEE case trimmer, spinning the case in my cordless drill, if I have a "stained" case I just give it some "touch up" with 0000 steel wool. If it's real bad some crocus cloth (not emery cloth) does a fine job on the tough stuff. If I have a case that doesn't clean up with one or the other I toss it. Chances are that "stain" is corrosion that goes far beyond being just a surface stain.

 

[supergoat343]

Thanks for all of the advise. Ill try the Vinegar First. Then maybe ill invest in some walnut lizard bedding.