Enigman
starting to spend too much on rocks
Member since December 2013
Posts: 163
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Post by Enigman on Sept 8, 2020 15:29:41 GMT -5
Hi all,
I am having a heck of a time getting a good final polish on glass in my vibe polishers. I am currently tumbling a lot of glass in bean shapes ranging from 1/4 to 1 inch in size. The source material is commercial fire pit glass. I am using Diamond Pacific MT4 vibe polishers (3 machines) with about 2 pounds of glass in each machine. I also include some large ceramic media to fill in the hoppers to the appropriate level. I am generally using aluminum oxide polish with a touch of borax to suppress foaming. No matter how long I run the batches the stones come out with dull spots in the concave areas or on flat areas of the stones. The dull area has a sharp delineation all around. So basically the edges and rounded areas are polishing well while non-edges are not. I have run the batches for at least a month in some cases with little to no change to the dull spots. I start with 2 tablespoons of polish in each 4 pound hopper and periodically add another tablespoon of polish about every 10 days.
I have also tried cerium oxide and running with or without borax. I have sometimes pre-polished with 1000 grit AlOx. Nothing I do to change the formula seems to make any difference.
I used to be able to do glass polishing successfully all the time although the stones tended to be larger. Then I moved to a new state and when I setup again everything went snafu.
Any feedback on how to get this worked out would be appreciated.
Thanks.
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Post by Jugglerguy on Sept 8, 2020 15:45:54 GMT -5
How much ceramic media are you using? Are you using the small stuff so it can get into the concave parts? I would use over 50% small ceramic media. jamesp is the glass expert, so maybe he can help.
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Enigman
starting to spend too much on rocks
Member since December 2013
Posts: 163
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Post by Enigman on Sept 8, 2020 15:53:20 GMT -5
How much ceramic media are you using? Are you using the small stuff so it can get into the concave parts? I would use over 50% small ceramic media. jamesp is the glass expert, so maybe he can help. I am adding ceramic by sight. I divy up the stones across the 3 machines and then drop handfuls of ceramic in the hoppers until the top of the rolling mix is at the right height. I'd guess each hopper has about 33% ceramic.
I thought about the smaller ceramic, but I phased out its use long ago and don't have any now. But in these batches the bulk of the stones (60%) are about 1/4 inch round so I would have thought there is plenty of small point contact.
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,154
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Post by jamesp on Sept 8, 2020 16:08:53 GMT -5
Guessing the problem is the large ceramic media.
Glass rubbing on glass seems to not abrade well. Glass rubbing on Mohs 7 pea gravel or certainly ceramics abrades well.
I say do what Rob says to do, use smaller ceramic media(I use quartz pea gravel) to get rubbing action into those concave zones. Obviously the 1/4" glass is rubbing the concave zones, obviously they are not abrading the concave zones.
A batch of 1 inch stuff has more rubbing force than a batch of 1/4" stuff. A tumbler full of BB sized tumbles may take months and months to polish. I batch of 1/4" stuff with a 1/2 pound chunk in it will be a total game changer, then the 1/4" stuff will polish.
Your statement: "I used to be able to do glass polishing successfully all the time although the stones tended to be larger."
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Enigman
starting to spend too much on rocks
Member since December 2013
Posts: 163
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Post by Enigman on Sept 8, 2020 16:48:58 GMT -5
Glass rubbing on glass seems to not abrade well. Glass rubbing on Mohs 7 pea gravel or certainly ceramics abrades well.
Good point. I do have some high quality quartz pebbles that I use for the earlier stages. I'll switch to those for the next polish batches.
A batch of 1 inch stuff has more rubbing force than a batch of 1/4" stuff. A tumbler full of BB sized tumbles may take months and months to polish. I batch of 1/4" stuff with a 1/2 pound chunk in it will be a total game changer, then the 1/4" stuff will polish. Your statement: "I used to be able to do glass polishing successfully all the time although the stones tended to be larger."
LOL Also a good point. I used to drop a big rock in batches that I thought needed to be stirred more. I already have some golf ball sized semi-polished stones on hand.
When I moved I also got older compared to my previous polishing back in the old state. So there's that. It's amazing how much one can forget over time.
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,154
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Post by jamesp on Sept 8, 2020 18:27:00 GMT -5
Sounds like it's just a matter of going back to the old methods. Only a few posts and memory is restored !
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