rollingstone
starting to spend too much on rocks
Member since July 2009
Posts: 236
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Post by rollingstone on Sept 28, 2004 14:38:00 GMT -5
Okay, this is one of those things that has just never made sense to me. How come I can tumble and wear down hard materials like quartz in the space of a couple of weeks, yet a soft rubber barrel and soft plastic pellets than can be scratched with my fingernail can be tumbled for years before they wear out?
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Post by krazydiamond on Sept 28, 2004 14:45:02 GMT -5
plastic (and modern rubber) is a manmade material and doesn't degrade or decompose like natural materials, much to the chagrin of environmentalists and people that don't want to live near landfills and old tire yards.
it's a molecular thing, i guess. you can reduce a rock over time to sand with water, but a lump of rubber will survive intact for almost forever. set a match to a rock and it won't burn, plastic does some weird and toxic stuff when it burns...
go figure, KD
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Post by docone31 on Sept 30, 2004 19:06:08 GMT -5
Ok, here we go. If I remember my chemistry correctly, rubber, plastics is organic chemistry. The grit wears the drum but it is hardly noticeable. The drum being flexible, and the rubber being soft the grit doesn't cut into the material like quartz and agate. Quartz and agate are not in the realm of organic chemistry. Some stones are. The grit slides across multiple planes, this produces a cutting action. The grit produces lines with each pass. This is how the stone is polished. Small chips are ejected from each pass and the lines score, and the high spots are taken down. There is also the pressure of the stones rolling against each other. This combined with the grit accelerates normal wear and tear. Hence, smooth and shiney stones.
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