herb
spending too much on rocks
Member since November 2011
Posts: 465
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Post by herb on Jul 28, 2023 16:32:17 GMT -5
Another mystery white powder post! Can anyone tell me about Levigated Alumina? I have a small container of it and wonder what it is used for. In my searching, some sites call it a pre-polish and others a polish. What is it used for? How does it compare to Tin Oxide? I there a reason to use one over the other, or are they just 2 different polishes? One site compared it to Linde A, B, C maybe it is used for polishing when faceting?
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Post by hummingbirdstones on Jul 28, 2023 23:03:24 GMT -5
Another mystery white powder post! Can anyone tell me about Levigated Alumina? I have a small container of it and wonder what it is used for. In my searching, some sites call it a pre-polish and others a polish. What is it used for? How does it compare to Tin Oxide? I there a reason to use one over the other, or are they just 2 different polishes? One site compared it to Linde A, B, C maybe it is used for polishing when faceting? Capt. John Sinkankas in his book Gem Cutting says: " Aluminum Oxide, Alumina, levigated alumina, diamontine, sapphire powder, ruby dust, ruby powder, Rudy Dix, Linde A, etc. All are chemically identical but vary in purity according to method of manufacture. Several, such as those with "ruby" in the common name, are made from crushed synthetic corundum. Linde A is the most carefully graded, showing remarkable consistancy in particle size. All are white except those made from synthetic corundum, which are pink. For practical purposes, aluminum oxide is insoluble. All are used extensively in polishing metals and gemstones. For tumbling or cabochon work in quantity, levigated alumina is popular because of its cheapness but does not polish as quickly or as well as Linde A, tin oxide, or cerium oxide. For soft or undercutting stones, Linde A has no peer when used on leather or wood." Hope that helps!
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herb
spending too much on rocks
Member since November 2011
Posts: 465
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Post by herb on Jul 30, 2023 19:50:23 GMT -5
Another mystery white powder post! Can anyone tell me about Levigated Alumina? I have a small container of it and wonder what it is used for. In my searching, some sites call it a pre-polish and others a polish. What is it used for? How does it compare to Tin Oxide? I there a reason to use one over the other, or are they just 2 different polishes? One site compared it to Linde A, B, C maybe it is used for polishing when faceting? Capt. John Sinkankas in his book Gem Cutting says: " Aluminum Oxide, Alumina, levigated alumina, diamontine, sapphire powder, ruby dust, ruby powder, Rudy Dix, Linde A, etc. All are chemically identical but vary in purity according to method of manufacture. Several, such as those with "ruby" in the common name, are made from crushed synthetic corundum. Linde A is the most carefully graded, showing remarkable consistancy in particle size. All are white except those made from synthetic corundum, which are pink. For practical purposes, aluminum oxide is insoluble. All are used extensively in polishing metals and gemstones. For tumbling or cabochon work in quantity, levigated alumina is popular because of its cheapness but does not polish as quickly or as well as Linde A, tin oxide, or cerium oxide. For soft or undercutting stones, Linde A has no peer when used on leather or wood." Hope that helps! Thanks for the info! That is pretty much all there is to know, I guess ;-)
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herb
spending too much on rocks
Member since November 2011
Posts: 465
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Post by herb on Aug 1, 2023 14:51:42 GMT -5
Well, I guess even with all that information, there is still something more for me to learn about levigated alumina! I had a batch of tumbles sitting around for a few years that needed some more polishing. The rounded corners were nicely polished, but some of the flatter areas were still dull. So I loaded up my lotto vibrating tumbler with the moist stones, added a teaspoon of my levigated alumina and let it run. After about 8 hours I decided to see how things were going so I pulled a few stones out to examine. Image my surprise when after washing and drying the stones I saw they were completely dull! Its been quite awhile since I tumbled anything so I'm not sure what I'd call the finish. I have another batch of stones that I'll start in a few days and take them up to 400 and then 1000 with silicon carbide grit and see how they compare to what the levigated alumina did to get an idea of how course it is. I guess the good news is that the levigated alumina was able to remove all traces of polish in 8 hours or less, so it is an effective grit, just not the grit I wanted or expected! Capt. John Sinkankas in his book Gem Cutting says: " Aluminum Oxide, Alumina, levigated alumina, diamontine, sapphire powder, ruby dust, ruby powder, Rudy Dix, Linde A, etc. All are chemically identical but vary in purity according to method of manufacture. Several, such as those with "ruby" in the common name, are made from crushed synthetic corundum. Linde A is the most carefully graded, showing remarkable consistancy in particle size. All are white except those made from synthetic corundum, which are pink. For practical purposes, aluminum oxide is insoluble. All are used extensively in polishing metals and gemstones. For tumbling or cabochon work in quantity, levigated alumina is popular because of its cheapness but does not polish as quickly or as well as Linde A, tin oxide, or cerium oxide. For soft or undercutting stones, Linde A has no peer when used on leather or wood." Hope that helps! Thanks for the info! That is pretty much all there is to know, I guess ;-)
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