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Post by gmitch067 on Aug 18, 2017 21:34:21 GMT -5
1st – The Questions:
Q-1: Can I apply a different polish to an already polished stone WITHOUT having to re-tumble again at a previous stage to strip off the old polish?
Q-2: On a molecular level, will a second type of polish react in a negative manner to changes brought about by the first polish used? (Note: I know from experience that using the big three polishes one after the other is not explosive – my garage still stands!)
2nd – Why I need the answers:
Previous shine was OK, but I want a better one.
…and/or…
The hard areas take a good shine, but the softer areas do not (like some Jaspers with all those sea critters and their homes trapped inside – or the complex and beautiful flows of Pietersite)
3rd – Thoughts behind the questions:
I gather that there are 4 ways to make my shinys shine :
1. Coat the stone’s surface with another substance that shines (or will take a shine) – like varnish, aquarium water, spit, or olive oil with a hint of rosemary – like Amber (maybe not… I get a shine on Amber with toothpaste… Ewww!… Sin!).
2. Sand/grind the surface with finer and finer grits (80 to 1-Bazillion grit) until the poor thing doesn’t have any choice in the matter - like Obsidian.
3. Cleave a section of the stone to reveal a shiny surface - like Diamond.
4. Use a chemical polish to re-arrange the molecular surface of the stone (Aluminum Oxide, Cerium Oxide, Tin Oxide, …etc…) – The Tumbler’s paradise!
In this thread I would like us to focus on #4… Using a chemical polish…
(You can probably argue that in a mixed hardness stone, the harder sections can successfully polish using very fine grit sanding/grinding, and a chemical polish can be used successfully on the softer substrates – I don’t know of a good example of this … maybe Pietersite??)
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Post by Rockoonz on Aug 19, 2017 10:54:06 GMT -5
I kind of like the olive oil and rosemary option, love the smell of rosemary. It was awesome when I accidentally hit the rosemary in the back yard with the weedeater until I told the wife...
Trying a different polish is not a problem, lots of people have their secret polish blends that work for them. If your polish is uneven across the stone surface it may be something other than polish, though.
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Post by Jugglerguy on Aug 19, 2017 11:33:06 GMT -5
It is my understanding that the oxides you list in #4 do not react chemically with the rock, but rather do what you describe in #2. Aluminum oxide is what I use in several steps of my tumbling method, I start with 500 grit, then 1000 grit, and finally polish, which is just very, very fine particles do the same stuff, something like 14,000 grit, I believe. So to answer your original question, there is nothing to strip off. It's not some sort of coating,
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Post by captbob on Aug 19, 2017 13:14:19 GMT -5
Agreed. Polishing a rock isn't like putting a coat of wax on your car. ETA: hmmm... just thought of something to try next time I have the wax out
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Post by tims on Aug 19, 2017 14:30:39 GMT -5
As stated above, the "chemical polishes" you list are just different kinds of abrasives. They don't add a layer of polish like wax or varnish, they smooth the surface to the point that it is glassy and shiny.
Putting a shine on softer materials might not be doable with abrasives, or if so might require a lot of experimentation and practice. Even the vets here sometimes struggle with softer materials. If it's really soft like calcite (common in fossil material) tumbling in any abrasive might destroy it. For fossil material I'd be tempted to research preservation techniques instead of lapidary. thefossilforum.com is a good resource for fossil ID and preservation methods.
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Post by coloradocliff on Aug 19, 2017 15:44:43 GMT -5
As stated above, the "chemical polishes" you list are just different kinds of abrasives. They don't add a layer of polish like wax or varnish, they smooth the surface to the point that it is glassy and shiny. Putting a shine on softer materials might not be doable with abrasives, or if so might require a lot of experimentation and practice. Even the vets here sometimes struggle with softer materials. If it's really soft like calcite (common in fossil material) tumbling in any abrasive might destroy it. For fossil material I'd be tempted to research preservation techniques instead of lapidary. thefossilforum.com is a good resource for fossil ID and preservation methods. Nailed It !
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Post by gmitch067 on Aug 19, 2017 15:50:43 GMT -5
It is my understanding that the oxides you list in #4 do not react chemically with the rock, but rather do what you describe in #2. Aluminum oxide is what I use in several steps of my tumbling method, I start with 500 grit, then 1000 grit, and finally polish, which is just very, very fine particles do the same stuff, something like 14,000 grit, I believe. So to answer your original question, there is nothing to strip off. It's not some sort of coating, Interesting! If the oxides are nothing but fine+++ grit, why is there a difference in how stones take a polish with certain oxides and not others? (For instance, Covington's list of recommended polishes show only Cerium Oxide for Obsidian... not Tin Oxide or Cromium Oxide as the best?)
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Post by Jugglerguy on Aug 19, 2017 16:00:53 GMT -5
I'm not sure that there is a difference, at least for obsidian. I've polished it with both aluminum oxide and tin oxide. I haven't used cerium oxide. In fact, I think most obsidian polished by members of this site since I've been here has been done with aluminum oxide. Cerium oxide was popular before I started tumbling, but it's very expensive now, so most of us use aluminum oxide with excellent results. The makers of the Lot-O tumbler say in the directions that cerium oxide does not work well with the Lot-O. I don't know why that is. Obsidian batch
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Post by gmitch067 on Aug 19, 2017 16:06:41 GMT -5
As stated above, the "chemical polishes" you list are just different kinds of abrasives. They don't add a layer of polish like wax or varnish, they smooth the surface to the point that it is glassy and shiny. Putting a shine on softer materials might not be doable with abrasives, or if so might require a lot of experimentation and practice. Even the vets here sometimes struggle with softer materials. If it's really soft like calcite (common in fossil material) tumbling in any abrasive might destroy it. For fossil material I'd be tempted to research preservation techniques instead of lapidary. thefossilforum.com is a good resource for fossil ID and preservation methods. Thank you all for your inputs. I see now that I have been operating under the misconception that the polishes are chemical... though I do remember hearing that Chromium Oxide is mainly used on softer stones that are prone to undercutting. Your inputs now show me why this is an issue when considering working with multiple strata stones (undercutting away the softer strata).
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Post by gmitch067 on Aug 19, 2017 16:21:18 GMT -5
I'm not sure that there is a difference, at least for obsidian. I've polished it with both aluminum oxide and tin oxide. I haven't used cerium oxide. In fact, I think most obsidian polished by members of this site since I've been here has been done with aluminum oxide. Cerium oxide was popular before I started tumbling, but it's very expensive now, so most of us use aluminum oxide with excellent results. The makers of the Lot-O tumbler say in the directions that cerium oxide does not work well with the Lot-O. I don't know why that is. Obsidian batchJust received 5 lbs. Aluminum Oxide from The Rock Shed and will start using it to see the difference. My experience polishing Obsidian has been limited to creating cabs using hand sanding (80-3000 grit) and polishing with Cerium Oxide (applied with dremel tool on a leather bed). After seeing your Obsidian batch post, I will switch over to AO! Later when I have a QT66 barrel free, I will try tumbling a load (Mahogany Obsidian purchased at The Consolidated Rock & Mineral Shop here in Vacaville).
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Post by Jugglerguy on Aug 19, 2017 16:37:14 GMT -5
I'm not sure that there is a difference, at least for obsidian. I've polished it with both aluminum oxide and tin oxide. I haven't used cerium oxide. In fact, I think most obsidian polished by members of this site since I've been here has been done with aluminum oxide. Cerium oxide was popular before I started tumbling, but it's very expensive now, so most of us use aluminum oxide with excellent results. The makers of the Lot-O tumbler say in the directions that cerium oxide does not work well with the Lot-O. I don't know why that is. Obsidian batchJust received 5 lbs. Aluminum Oxide from The Rock Shed and will start using it to see the difference. My experience polishing Obsidian has been limited to creating cabs using hand sanding (80-3000 grit) and polishing with Cerium Oxide (applied with dremel tool on a leather bed). After seeing your Obsidian batch post, I will switch over to AO! Later when I have a QT66 barrel free, I will try tumbling a load (Mahogany Obsidian purchased at The Consolidated Rock & Mineral Shop here in Vacaville). All the obsidian I have ever tumbled has been done in a Lot-O vibratory tumbler. The best rotary tumble obsidian I have seen was done by captbob. I think he let it roll for something close to eternity.
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Post by johnjsgems on Aug 23, 2017 11:36:31 GMT -5
Covington's chart is a throw back to the peak years of lapidary 60's - 70's. Cerium was $5 per lb. Tin oxide about $10. Linde A was sold by the ounce and pretty expensive but can't remember. Cerium was tried first, then tin and on buffs at least you broke out the Linde A. The aluminum oxides were primarily pre polish or fine grits (600, 1000, 1200). Now they grind it down to very fine (like .3 micron which equals Linde A for a lot less)and the sub micron AO polishes a much wider range of hardness. What works best for any particular rock is largely trial and error. Best to accept it and enjoy rather than worry too much why. Like parents say "because I said so" in lapidary it is "because it works".
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Post by gmitch067 on Aug 23, 2017 17:32:52 GMT -5
Good info and advice John & JS. Thank you.
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