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Post by Bob on Nov 2, 2020 11:16:08 GMT -5
What do you think would happen if I put only 1 rock in a barrel with no other rocks but only plastic beads to complete the barrel fill on a polish run?
My reason for asking is in a situation where I wanted to test which polish worked best on a rock I had never done before and I wanted to go the extra mile to make sure this rock 1) doesn't mess up a polish run on any other types of material I have and 2) I don't want the other rocks to screw this one rock up and 3) in some cases the one rock is expensive and I only want to buy one of them.
I would use the smallest barrel possible.
If I were to make a prediction on this, because I don't think I've ever done it, it might be that it will work just fine or that at least one other rock is necessary to polish properly. In other words, I wonder if plastic beads in a polish run only cushion or do they in and of themselves also function as "polish-rubbing" media against the targeted material?
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Post by Starguy on Nov 2, 2020 11:45:40 GMT -5
BobMy personal opinion is that it wouldn’t work very well. The ratio of rock to pellets to water would be a SWAG. Too much water and the pellets will float above the rock without exerting any polishing pressure on the rock. Too little water and the pellets would just stick to the rock. My experience is totally rotary tumbling. Some of the vibe guys might have different thoughts. Have you considered using ceramic media? It seems to me that would be the better choice.
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Post by miket on Nov 2, 2020 14:18:23 GMT -5
I'm with Brent on this one. Take it for what it's worth because I'm definitely no expert, but I think ceramics might work better.
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Post by Bob on Nov 2, 2020 14:45:05 GMT -5
Rotary only here.
I'm not worried about floating part because I don't put enough water in to trigger that. But, for the first time, you've caused me to think about ceramics (which I also use) vs. plastic pellets and their behavior that might be very different in the way they rub against rocks in polish stage.
Occasionally when I do the pour out when a batch is finished, a rock will come out and land in the plastic pellets in my strainer. The more slippery the rock is, especially in polish compared to earlier grinds, the more that rock just dives to the very bottom of the pile of plastic pellets and has to be fished out with fingers. But this doesn't happen with falling into ceramics due to the mass I guess of the ceramics.
So, now I'm thinking of the internal cascade face as the barrel rotates. If all the filler is plastic pellets, maybe those rocks are just diving to the low side of the barrel and not getting rubbed near as much as if ceramics (or small rocks) instead of plastic pellets.
If we are onto something here, it might be that once the % of plastic pellets goes above a certain amount, processing efficiency in polish at least might decrease. Never thought about this before. I've got to think about this vs. the risk of the internal cracks I've seen in many of the ceramics I've purchased.
I suppose one way to avoid the potential grit carryforward contamination risk, would be the change my methods. Normally I knock off the roughness of the new large "porcelain" ceramic pieces in rough grind and now then then also use in 220, 600, and 1,000 prepolish. Due to those internal cracks I stopped letting ceramics go into polish a few years ago. Another approach I guess would be to never get the ceramics in rough grind at all, but just make a run or two in 600 or 1,000 to smooth them up and then use them in polish and have dedicated ceramics always used only in polish.
Hmmm...another one of the zillions of variable to check out...never ends.
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Post by pauls on Nov 2, 2020 14:54:23 GMT -5
I'm going to disagree on this,It will work. Only one way to find out for sure Bob, give it a go. Too many plastic pellets in a vibe is no good it cushions that well that it stops the vibe action, in a rotary should be no problem.
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Post by Bob on Nov 2, 2020 15:04:55 GMT -5
Thanks pauls. I bought some of those tiny ceramic balls that are only 1 or 2mm in diameter to test in polish someday but have not yet tried them.
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Post by Mel on Nov 7, 2020 22:54:41 GMT -5
Waste of time; no friction from the plastic. Large ceramic media might do the trick though; I'd try angle cut because I've read that the balls tend to flatten out.
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