Slow Motion Sandblasting

[hdwhit]

I had previously posted about using alternative media for case tumbling. One of the media I thought might hold out some promise was alluvial sand. Well, over Columbus Day, I acquired some Spring River alluvial sand and tested it out on some cases that were in my recycling bin because they had gone beyond tarnish to blue-green corrosion.

I tumbled the cases overnight with my rotary tumbler on its last legs. I will try to get some photographs posted soon, but the effect is very hard to capture on my phone's less-than-great camera.

The sand did indeed virtually erase any trace of the corrosion. I was not able to detect any measurable dimensional changes using a micrometer. So, that part of the experiment seems to have been a success. What was not "successful" was the surface of the cases had the matte appearance we would associate with a sandblasted surface. Because the grains of sand were so small and uniform, the surface was very smooth but not at all reflective.

Tumbling the cases overnight in walnut media made essentially no change. So as a way to remove surface corrosion, rotary tumbling in sand seems to work very well. It does however ruin the jewelry-grade shine that many people are looking for with their brass.

 

[higgite]

Have you inspected the cases under magnification? I’ve never tried sand (and won’t) because I heard or read somewhere that because silica is harder than ammo brass, it not only scratches it like you described (dull finish) but will actually embed in the brass and do a number on your dies and maybe your chamber. That could be just talk, but it gave me reason to pass on it. Good luck it and I hope you it doesn’t turn out to be an expensive experiment.

 

[Fine Figure of a Man]

The scratches in the brass will also cause it tarnish faster.
If you look at the sand you used under magnification you will see the brass that has been removed.
I could see using sand to salvage badly corroded brass that is hard to come by or very expensive.
Wet tumbling with SS pins would be a better option.

 

[Nature Boy]

Maybe vibrator tumbler would work better

 

[hdwhit]

higgite wrote:
Good luck it and I hope you it doesn’t turn out to be an expensive experiment.

It won't. I have already decapped, acid washed, inspected, sized and tumbled every servicable 30 Carbine round I own. None of it has been tumbled in sand. Since I no longer have an M1 Carbine, all of my Carbine brass will all be converted to 5.7mm Johnson/22 Spitfire brass after I retire and relocate. If my 30 Carbine dies are damaged after this, it is no loss since I will no longer have brass to go into them.

 

[hdwhit]

drunkenpoacher wrote:
If you look at the sand you used under magnification you will see the brass that has been removed.

Thank you.

When my oldest moved out, we didn't put his laboratory microscope in the garage sale. Turns out that was a good decision. Now, I just have to find where we stored it....

 

[Blue68f100]

Using something that abrasive would require you to wash the brass to remove any dust to prevent from scratching your dies. Something I want take a chance on. There are a lot of abrasives that will clean each has there own set of problems and advantages. It's hard to beat the tried and proven of corncob, walnut hulls, SS pins. Even the chemical cleaners work very well and fast if you want speed. you just have to neutralize the acid afterwards.

You could just setup a small blasting cabinet and use soda ash to clean them too. That what makes the SS pins so good. Hard enough to do some tough cleaning and not have any residue sticking to the brass to deal with.

 

[mdi]

When I began tumbling I tried many different media. I used beach sand in a rotary tumbler, and while it was pretty aggressive, it left the brass with a matte finish. I'm not into glossy, shiny, virgin looking cases but the finish with sand was a bit too "matte" for me. There were no pits or scratches from sand, just an even, clean dull finish. Any brass tumbled without a wax or sealant in the media will tarnish quickly; nekkid metal exposed to the air...

 

[Sunray]

"...acid washed....and tumbled..." Whatever for? Tumbled is enough.
"...gone beyond tarnish to blue-green corrosion..." And they're still gone beyond tarnish to blue-green corrosion. The corrosion is the copper coming out of the alloy.
"...the matte appearance..." Is fine. Cases need to be clean, not shiney.