Enigman
starting to spend too much on rocks
Member since December 2013
Posts: 163
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Post by Enigman on Mar 26, 2014 16:48:25 GMT -5
Hi all,
I am looking for a consensus of opinion based on everyone's expertise.
A while back I bought a tumbling grit kit from a seller on eBay. It was all four stages of grit including polish. I used that kit on a batch of hickoryite and after months was never able to get a gloss of any kind. Much later I bought some 1000 grit pre-polish from a different source. It was a visual match for the "polish" from the previous eBay purchase. I wrote to the eBay seller and asked what his polish actually was. He said it was "1500 grit silicon carbide". Maybe it's just me, but I would consider 1500 grit, especially silicon carbide, to also be a form of pre-polish rather than actual polish. Then again, I'm not an expert on grits.
Can anyone render an observation on where 1500 grit silicon carbide falls in the scale of grit to polish?
Thanks.
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Post by Drummond Island Rocks on Mar 26, 2014 17:27:07 GMT -5
do yourself a favor and deal with a reputable dealer like "the rock shed" or "kingsley north" when it comes to your grits and polish. There's also a member here on the forum that sells supplies and that's a great choice too. The RTH members name is John and this his online store. www.jsgemslapidary.com/ you cant go wrong with him and if you have questions he will certainly have the answers. As for polish I only use aluminum oxide and would say that quality polish starts at one micron and high performance polish will be sub-micron. Here's a cheat sheet that compares microns to grit sizes thesharpenershop.com/2012/03/grit-size-versus-micron-size/Another way to look at it is that when cabochons are polished they are often done with 14,000 and even 50,000 diamond grit wheels Good Luck! Chuck
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Post by johnjsgems on Mar 26, 2014 18:44:36 GMT -5
Thanks Chuck. If the fourth step was white it was not silicon carbide. 1500 anything would indeed be a pre-polish. Likely the e-bay seller doesn't know what he is selling. Most commercial grit kits for rotary tumblers will have 60/90, 120/220, 500F, and some kind of polish. Sometimes the 500F SC is replaced with 600 aluminum oxide. Sometimes the polish compound is not the greatest.
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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 Mar 27, 2014 1:07:44 GMT -5
do yourself a favor and deal with a reputable dealer like "the rock shed" or "kingsley north" when it comes to your grits and polish. There's also a member here on the forum that sells supplies and that's a great choice too. Yeah ... well ... that was back when I first bought my tumbler and I immediately got a grit kit to go with it. I now get my stuff from The Rock Shed and other dedicated folks. Thanks for the pointer. I'll check that out. Well, that certainly explains a lot. I tried for months to get a gloss using that first batch of what turns out to be pre-polish. I have since purchased aluminum oxide polish and the one time I have used that so far the stones glossed right up. According to the chart, 1500 grit is about 14 times too course to be polish. I'll be sure to let that eBay seller know in specific terms, not that they will likely care, but me being me, I'll tell him anyway. Thanks so much for the info. Ya gotta love forums like this for learning from others.
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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 Mar 27, 2014 1:18:36 GMT -5
If the fourth step was white it was not silicon carbide. 1500 anything would indeed be a pre-polish. Likely the e-bay seller doesn't know what he is selling. Most commercial grit kits for rotary tumblers will have 60/90, 120/220, 500F, and some kind of polish. Sometimes the 500F SC is replaced with 600 aluminum oxide. Sometimes the polish compound is not the greatest. The stage 4 stuff I am asking about is a khaki-gray color. My current polish is white aluminum oxide. Now that I know what the gray stuff really is, I can use it for pre-polish. Yeah, the eBay seller was not the best. I ordered hickoryite rough and the grit kit together. It took weeks to get the package and it was only the stones. I had to go back and get the seller to ship the grit like pulling teeth. I checked out your site. Lots of great stuff there. It's in my bookmarks now. Thanks.
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,563
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Post by jamesp on Mar 27, 2014 5:45:35 GMT -5
A close up of aluminum oxide before it is used. As it is tumbling each particle gets smoother adding to the polishing effect.
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Bains
off to a rocking start
Member since December 2004
Posts: 12
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Post by Bains on Mar 27, 2014 6:46:58 GMT -5
This forum is absolutely fantastic. As a newbie I am struggling to get some consistency and a reasonable end result. Enigman seems to be about 4 to 8 weeks ahead of me in experience and his questions mirror mine. The answers of the group are always thoughtful and very factual.
Thanks to everyone.
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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 Mar 27, 2014 8:54:09 GMT -5
A close up of aluminum oxide before it is used. As it is tumbling each particle gets smoother adding to the polishing effect. Cool pic. Aluminum oxide (Al 2O 3, also known as "alumina" or "clear sapphire" or "corundum") amazes me. It is a metal that acts like clear crystal, extremely tough, and about as close to 100% transparent as you can get, and all just by adding oxygen atoms to aluminum. I remember one of the Star Trek movies, number 4 I think, where they needed a huge slab of strong transparent material for a whale tank. Scotty said that they needed "transparent aluminum". I thought the writers just made that up. Turns out that it is real. Recently I saw an episode of "How Do They Do It" where they showed a company that grows huge Sparklets Bottle sized nodules of aluminum oxide. They then drill 3 and 4 inch diameter cores out of it and then slice the cores into thin plates that they call Sapphire Glass. The plates are used for making windows for all manner of high tech devices that need a flawless, super tough, scratch resistant and highly transparent cover glass, such as IR tracking and targeting domes on helicopters. Strangely, although it grows like a crystal in an organized lattice, the shape of a grown crystal nodule is not hexagonal or octahedral like the lattice. Instead it looks more like fractured glass or resin that has been hardened in a bag. Normally that would indicate a relatively soft randomly organized crystal like obsidian and glass. Instead it is very hard in any sized crystal. The company I mentioned speculates that if they could grow large enough nodules of it, they could use it to make bullet proof windows for aircraft and cars. Atomic structure is just amazing. If you were going to set out to design a "tinker-toy/erector set" way of building a 3D reality existence, what better design could you come up with than atomic structure? You take one of these things and combine it with those things and PRESTO it does this and that. And yet even more amazing ... if you smash one of those single atoms into it's own pieces, you get more out of the process than seemed to exist in the first place. According to particle physicists, this is analogous to smashing two cars together at light speed and out of the crash comes two locomotives and an aircraft carrier. It all just blows my mind. I wonder if you could find chunks of aluminum oxide and tumble them into high gloss hyper-clear stones?
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,563
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Post by jamesp on Mar 27, 2014 12:18:15 GMT -5
I have enough hard stuff to tumble without graduating to AO Interesting subject Enigman. Amazing what technology can do.
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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 Mar 27, 2014 14:20:40 GMT -5
LOL ... I'm quoting myself here, but I wanted a subject reference and I just had to share the results. I tried to point out to the seller that 1500 grit is not in fact polish. He defended saying that although he was aware that it didn't work for obsidian, he used to offer aluminum oxide years ago and he switched to 1500 SC because he thought it worked better (aka faster) and he has only had one complaint. I pointed out that if it is known not to work on obsidian, then it also doesn't work on fluorite or any other soft stone, and a lack of complaints does not necessarily denote that it was a good switch. It just means that folks didn't make the connection between his pre-polish being advertised as polish and their inability to reach a gloss. I suggested that he "consider" identifying the grit number for the polish like he does for all the rest of the grit stages and let the buyers decide up front if that's the right fit for their stones, or even offer a five grit kit specifically for soft stones with the 1500 as a pre-polish and some aluminum oxide actual polish. You know ... be up front with what is being sold and shoot for the best outcome. At this point the seller devolved into name calling. Okay then ... end of conversation. Thanks a bunch. Have a nice daaaaay. LOL. Any-who, thanks to all who have answered this question. All great stuff.
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