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Restoring Over-Tumbled Bright Aluminum
Article © MAIL User: CherryFire

This article specifically addresses the 'gray grunge' that can happen to over or incorrectly tumbled bright aluminum. I've found this method of polishing also gives fantastic shine to stainless, but it's probably overkill to say the least.

I use the following equipment, for reference:
Rio Grande mini rotary tumbler (double barrel - I keep one for wet and one for dry)
Rio Grande stainless steel shot
Walnut shell (obtained from a pet store in the lizard bedding area)
Super Sunsheen burnishing compound
Distilled water - I have found that regular tap water is inferior, but I'm sure it varies from area to area
Baking soda

Step one - Clean the barrel

Before even trying to clean the aluminum, clean the tumbler barrel with baking soda and a little water. An old toothbrush makes this easy. Give it a good scrub and rinse very, very well.

Step two - Is your shot grungy too?

If you've really mauled your aluminum, you may also notice that your shot has lost its shine and color. Put the shot back in the barrel, add distilled water to cover, and add approximately three drops of Sunsheen. Run for an hour, drain and rinse. Repeat until the water is clear when you pour it out.

Step three - Dry media, round one

Your barrel must be completely dry before this step, which is why I find having two barrels really helpful. Put your pieces to be restored in first, then add walnut shell until the barrel is 3/4ths full. I add a used dryer sheet whenever possible, based on information gleaned from machinist forums, and while not necessary, it definitely seems to speed the process along and keep the walnut shell more effective for a longer time. If you don't have dryer sheets, a paper towel cut up into squares is a good substitute. Tumble overnight, or 8 to 12 hours.

Step four - Into the shot

At this point, color and luster will be improved, but still not where we want to be. So into a clean barrel it goes, with 2 pounds of stainless steel shot. Add distilled water to cover and then about half an inch more. Add the three drops of Sunsheen again, and tumble for 2 hours. Check it, tumble for 2 more hours if desired. Continue until the rings are within one to two shades to the original/desired color.

Important caveat: I have tumbled a piece in shot + Sunsheen for 4 hours at a time, with continued improvement. I have NOT tested longer time frames yet. Checking the water and replacing when it starts to turn gray is VITAL.

Step five - Back into the walnut it goes

This is just a repeat of step three. Dry barrel, dry walnut (you can save and reuse the walnut many, many times), dryer sheet. Replace the dryer sheet when it gets medium to dark gray. I always let this go at least 6 hours, preferably 12. This step will lighten the metal just a touch more, and most importantly - will give it a brilliant shine. There is no such thing as too long in the walnut shell- you can let it go as long as your patience allows, though you will hit a point where further improvement isn't possible.

Step six - Still not happy?

With one really stubborn piece, I've had to repeat step 4 and 5 again. If you're not seeing results, make sure your water is clean in step four, and replace the dryer sheet/paper towels in step 5. Each step has times that I've tried and have found to be successful. I encourage you to experiment with these times, considering this method is still new to me. I have successfully restored about half a dozen pieces, but have run out of test chain to work with.

Results and other information

The below picture shows a 'before' chain, the same chain after step five, and a comparison piece that was never ruined. The original before picture doesn't show how fantastically I destroyed these rings - I spent a couple of days trying other solutions that wound up turning the rings nearly black and completely matte. I didn't think to take pictures at that time, and I have no desire to go through salvaging my shot again.

Image: tumbling.jpg

The chain shown as an example can absolutely be restored completely with additional passes through the shot then the walnut. Sometimes I've noticed the grunge is more persistant than others, and on finished pieces the weave can have affect the total time needed to restore a piece.

Just for reference, I have also experimented with and have not been pleased with (when it comes to recovering BA):

White rice
Auto polishing compound w/shot (such as Blue Magic, Mother's)
Shot with blue dawn
Ammonia/soap/water mix (I was getting desperate)

As of 1/25/10, I've also ordered some TumbleDry Green - which is walnut shell impregnated with chrome oxide. Chrome oxide is sometimes referred to as "green jeweler's rouge". My research has shown that it is recommended for the 'white' metals, such as aluminum, stainless steel, and silver. Its counterpart, red rouge, is recommended for brass, copper, and gold. If this proves more effective than plain walnut shell and can reduce the time needed, I will update this article with an improved method.
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