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Post by fernwood on Jul 17, 2018 7:48:00 GMT -5
Think I am getting a fairly good handle on the different types of grits and what their best uses are. The polishes are still a little confusing.
When I started tumbling again, all I had was some grits/polishes left over from the 1980’s. The grits and pre-polish were marked with sizes standard for that era. The containers of polish were just marked polish. One was white and the other pink.
I “advanced” to a Thumblers Tumbler package of 4 sizes of grit/polish, but the polish was not marked with size.
Recently purchased some bulk grit/polish on RTH. The sizes were:
SiC 80
SiC 120/220
SiC 500
White Aluminum Oxide 1200
I had read here that the 1200 is more of a pre-polish than polish, so was curious. When it arrived appeared to be identical to what was contained as polish in the Thumblers Tumbler packet.
Did some checking of online resources for polish and none listed the size. Most list Aluminum Oxide polish, or “our polish”.
So, how do you determine the actual size of the polish if it is not listed? Call or email to ask?
I am also looking for recommendations on the best type of polish to use for softer stones or those with undercutting potential. On the first batches, I did a 5 step process. The extra step was combining pre-polish and polish. This worked well for harder stones. There was undercutting on some of the Granites and fossils which had been fine until this step.
I am omitting the extra step for the cabs and Tears this time.
Trying to determine the best process to tumble a variety of cabs in my HF duel barrel tumbler. Any assistance appreciated.
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Post by deb193redux on Jul 17, 2018 12:27:00 GMT -5
The pre-polish oxides are about 1000g or 1200g. I use the 1200g or 1500g silicon carbide. My thought is that the oxide pre-polish are more for polish pads, but I know some use them in the tumbler. A "polish" grade oxide is usually 50,000g to 60,000g. The 60K is roughly 1/2 micron. You may see the polish size in microns. The super-fine polishes are 100,000g or 1/4 micron. Most f th eoxides come this fine, but AO is the most commercially available 1/4 micron offered. On a pad, the choice of oxide can be critical, as well as the amount of dampness and/or heat allowed. In a tumbler, I have found AO to be a good general purpose polish, even for softer stones. Often in the polish step, enough cushioning to prevent chipping or crazing is more critical than the oxide used. good luck comparison chart: www.gessweincanada.com/category-s/11328.htm
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Post by fernwood on Jul 17, 2018 13:13:12 GMT -5
Great info, thanks.
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Post by pauls on Jul 17, 2018 16:35:02 GMT -5
Hmmm 99 The old grits and polish in the glass jars trick. I wouldn't worry too much about it, use them up. For what its worth the pink would be Cerium Oxide, good for softer stones glass Obsidian Opal etc. The white could be any number of things, Al Oxide, Tin Oxide, who knows? I would just use it and see what happens, if its marked polish it probably is.
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Post by aDave on Jul 17, 2018 18:50:44 GMT -5
Hmmm 99 The old grits and polish in the glass jars trick. I see what you did there...
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J Mee
off to a rocking start
Member since July 2018
Posts: 21
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Post by J Mee on Jul 18, 2018 1:40:58 GMT -5
It is pretty much impossible to tell prepolish from polish visually, so make sure you keep the white one marked polish seperate! Often old kits had AlO2 “sapphire powder” as a pre polish and polish, but it could be several other oxides. If it were in my pile I’d use it on things I wantsed aluminum oxide for and if it didn’t turn out well try some known AlO2 polish and see if I got the same results.
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