Brass stained in Vibatory Tumbler.

[Four Fingers of Death]

I have been polishing a heap of brass over the past month or so, having got a good supply of crushed corncobs after somewhat of a drought and had accumulated a backlog of dirty brass.

The corn cobs have been combined with a decent glug of Nu Polish following a recommendation of a member here and the results have been excellent.

Yesterday I tumbled some 223 brass (commercial Winchester) that had been sitting for a couple of years. It wasn't particularly dirty when I threw it in(I think th eonly powder that those cases would have seen is 748). I pottered around for a few hours and went to pull it out and this was what it looked like:

http://i89.photobucket.com/albums/k228/4fingermick/Reloading%20and%20Casting/20121101-02WeirdBrass.jpg

http://i89.photobucket.com/albums/k228/4fingermick/Reloading%20and%20Casting/20121101-02WeirdBrass3.jpg

I don't know what caused it, but I took it upstairs and drowned it in hot water with a decent slug of laundry detergent. I went back about an hour later and tipped it out, black flakes went everywhere. I replaced the water and there was still a good amount of soap in the brass, so I left it overnight. Here is the result:

http://i89.photobucket.com/albums/k228/4fingermick/Reloading%20and%20Casting/20121101-02WeirdBrass2.jpg

This pic is a tad blurry, but you can see that it came good and is pretty well ready to load.

As I have around 50lb of corn cob media downstairs, I will dump the current stuff and start again.

Amazing what a wash will do.

[Stampede]

I’m not 100% exactly sure what has happened, but it looks like there was a modest chemical reaction caused by the polishing media and the case surface. Most likely there was some kind of wax, case-lube or protection substance on the cases. This in turn caused a reaction with the polishing media. Some stuff sticks to the brass for many years/decennia without you will ever notice it.

This phenomena is not that all uncommon and in many situations this can be “neutralised” with indeed (soapy) water or a very clean (new) batch of corncob/walnut media. And repeat the process again. Note: a similar thing can and will happen with stainless steel or ceramic media just as easily!

In some cleaning/polishing media there is pumice (or an other kind of abrasive) and ammonia, even in very minute proportions. This in combination with some kinds of lubes, waxes, oily substances and solvents will cause “cluttering”. This stuff sticks to the cases/brass. Most likely not only your brass was contaminated but also your media it self.

If it was a more aggressive chemical reaction it would have stained the brass, thankfully this was not the case. I do work industrially with metal cleaning/polishing media’s and processes/systems on a daily bases, it never ceases to amaze me to see what kind of crazy things can happen quit unexpectedly.

Stampede

[Moonie]

How often do you clean your tumbling media? I put a used dryer sheet in mine after a few loads, seems to get rid of most of the crud.

[runfiverun]

i'd say the nu-finish was all wet picked up the dust from the media and deposited it on the cases.
you probably could have scraped it off with a thumbnail.

next time throw a few ripped up dryer sheets in the dry media and you'll see the dirt/dust getting picked up in the dryer sheets.
then when you add the nu-finish let it run in the media alone for 10-15 minutes to get fully mixed in and warmed up then add the brass.
i like to only use the nu finish when the cases are cleaned to give them a good coating and keep that batch of media separate.

[leadman]

The nufinish was still wet. I have the same problem if I put my homemade polish in and don't let it run empty for 15 minutes or so.

[jcwit]

Media's to old and used up. WAY to much Nu-Finish added/used. You only need a teaspoon or 1 and a half per tumbler of new media.

This is a case where less is more.

[Four Fingers of Death]

The media was pretty new, only had done one or two runs. I definetly use too much Nu Polish, I will cut it back and save some money. It is quiet possible that I didn't let it mix in properly as well.

Those dryer sheets are amazing things aren't they? I have never used them in the dryer, lol, but have used them to good effect to de- static my scales.

Back to the drawing board so to speak! I will dig out the dryer sheets or buy some more, dump the media, wash the bowl out and start again.

Sure got my attention, that's for sure, haha!

[fatelk]

I had some brass do that one time. In my case it was brass that had been lubed and sized, then sat for a few years with the lube still on them. The lube had dried out and was kind of hard and sticky. Instead of washing them first, I threw them in the tumbler- big mistake.

[DukeInFlorida]

I have posted this a few times, and maybe some day, one of the mods will see fit to make my post a sticky. I cover the very best way to polish brass flawlessly.

http://castboolits.gunloads.com/showpost.php?p=1884440&postcount=12

The two keys are:
1) Add mineral spirits and NUFinish BEFORE adding any brass, and let that soak in for at least 15 minutes before adding any brass.
and
2) Adding the right amount of brass (see instructions!)

Read my write up, and try that and report back with results.

[Four Fingers of Death]

Thanks for that Duke. I'll try the lizard bedding who I use up the two huge bags of corn cob stuff I have.

[trixter]

I too experienced the "stain" for the first time a couple of days ago. My lizard litter is about a year old and I put polish in about every 3rd batch, I usually let it run for about 20 minutes to 'soak in', and always use dryer strips. I guess it's time for upgrading the lizard litter and a bowl wash. My results were not as dramatic as the photos, but a few splotches here and there. Thanks for the info.

[DaveInFloweryBranchGA]

If you still have some stain, my experience has been that sometimes you want to use citric acid to pre-wash the brass before tumbling. Removes stains, certain levels of corrosion and gets the brass pretty clean. Then I use a 50/50 mix of crushed walnut and corn cob media. I find this mix works better for me than either by itself. I follow the same basic regimen that Duke does and use the same chemicals in my media as well. Work great and is the minimum amount of work.