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What makes dry tumbling media break down faster than usual?

Q. We use oak in a vibratory tumbler for the final polish on our antiqued bronze jewelry line. Lately the jewelry comes out looking good, but your hands get dark sorting it because of the presence of tiny particles of infused oak. The oak media itself is breaking down after a week or so, requiring a new batch, with new added paste.

I have an employee who is not vigilant about drying the jewelry after it comes out of the 1st tumbling cycle and before it goes into the oak. Jewelry may be going into the oak tumbler wetter than it used to. Could this be the problem, and if so, could someone explain to me why, so that I can explain better why we insist on a thorough drying between the ceramic and the oak?
Many thanks
Kate

Kate Dwyer
manufacturer - Nevada City, California, US
January 10, 2012

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My biggest problem with oak organic media is it turns dark due to oils and other contaminants. However, it seems to deteriorate faster when water or moisture is added. My guess is that the media expands and has greater resistance and therefore becomes more abrasive to some extent, so that in turn shortens the life and performance of the media.

AF Kenton
retired business owner - Hatboro, Pennsylvania
January 19, 2012