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Post by Bob on Oct 13, 2021 11:30:13 GMT -5
There is a chance I asked about this once but in a different way. This is only about rotary.
When I first started getting some experience under my belt, I thought more of everything is better. So I would polish for 3 weeks, then I learned that it seemed no better than results after 1 week. I also tried that for burnish, figuring a week was better than the hour or two or three it seemed most others were doing. That too fell away when I started looking at results.
More or less these days, my burnish goal is about 3 hours. Sometimes I forget and let it run for more, such as overnight and it ending up being 10 or 12 hours instead of about 3. After having this happen a few times in last 3-4 years, it seems that one part of the results are predictable and another not.
If the batch has the basics in it, there seems to be no downside or damage. I also am not sure they are any shinier after more than 3 hour burnishing. By basics I include: crystal quartz, chert, chalcedony, jasper, agate, pet wood, tiger eye.
But if not the basics, then sometimes longer times in burnish start going weird on me. By these I mean feldspars, aventurine, rhodonite, unakite, glass, obsidian, lapis, etc. Sometimes the finish is worse after a long burnish run than before going in burnish! So I'm trying very hard to hold it to 3 hrs.
My burnish is ivory soap bars. I use a whole bar in a 12lb barrel and half in a 6 lb barrel and adjust proportionately for larger barrels. This makes for a very slimy run but it works for me and was suggested by an old timer who has mirror like shine on his rocks to prove it. In the empty barrel, I shave off the soap bar with a pocket knife, pour in a little bit of warm water to start it dissolving, then start adding the rocks.
Is there more or less agreement among other rotary tumblers here that too long in burnish can be counterproductive with some materials?
Logically, it kind of freaks me out how sloshing around in this slimy burnish mixture could degrade the finish on any kind of material.
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Post by Rockindad on Oct 13, 2021 11:52:21 GMT -5
We stopped doing any burnish when we were all rotary as I could not really tell a difference. Tried it a few times when we started with the vibes and stopped for the same reasons. Held some rocks back after polish and a thorough washing and burnished the rest, same shine. It should be noted that we do a very thorough washing after polish with hot water. When we did burnish it was usually measured in hours, anywhere from 4-8.
ETA: for the record, our municipality deems our water to be Medium-Hard.
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pizzano
Cave Dweller
Member since February 2018
Posts: 1,390
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Post by pizzano on Oct 13, 2021 12:49:55 GMT -5
From what I understand, burnishing, particularly with stone material, is nothing more than a final polishing step......a micro process if you will.
Therefore, some type of "friction" is still involved in the burnishing process. Be it ever so slight. Considering, to the best of my knowledge, Ivory soap bars contain molded, firm liquid detergents and little (if any) degradable solid materials, that once mixed/blended with a liquid (water), can become a creamy, almost paste like cleaning/soaking solution..........where/how is friction developed/applied/derived from a purely liquid agent (outside of the hard objects, stones) being tossed against each other cushioned by the liquid/creamy detergent......?
Curious, if the OP's burnishing stage includes the removal of any prior polishing slurry and the stones are absolutely void of any left over solutions/compounds......?
Historically, burnishing agents used or applied as to bring a final luster to an already hard polished object like stones, contain some type of friction bearing material. Like corn cob, walnut shell, rice, sugar, salt, even detergents like Borax or solid granular laundering material, that over time, when mixed with water, eventually soften or liquify to a point that still allows minutus friction properties........liquid detergent soaps, generally speaking, are not the agents that provide the friction. It's what is being used to apply the liquid to the surface of the object, that provides the friction required to burnish.
Many burnishing applications are also void of any liquid altogether........whether it's stone, metal, ceramic, glass, ect........dry friction.
Just a thought.
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Post by Bob on Oct 13, 2021 14:43:14 GMT -5
It is fun to read the theories about what happens to the surface in burnishing and how it might reach a certain amorphous, liquid-like state a few molecules deep. But it all seems mostly educated conjecture too when one reads carefully. I had never thought about dry burnishing of just the stones all by themselves. Wow--that would take some courage, but now that you've thrown out the challenge I might just give it a shot.
Before burnishing, this is my process. My last grit stage is 1,000. Then a good rinse maybe 8-10 times with clean water, jostling the rocks in a plastic rinse container a lot to get them all rubbed together. Then first week of polish is with polish only reused in that first week. All rocks are also dipped in water just before putting in the polish barrel just in case to minimize any dust contamination. Then after a week, repeat all that but with polish reused only in second week.
Then for burnish, I rinse thoroughly, but just in luke warm running water, also dipping in clear water just before putting them in the barrel. All my rocks are taken to perfection, so there are no pits or cracks propagated after coarse grind. Unless there is some rock worth keeping, such as ever-fractured-it-seems amethyst, and for that I Opticon all fractures just before or just after 1,000 SC.
I have no scientific way of measuring shine improvement. As I lay out the wet rinsed rocks, I determine whether I can tell which ones are wet and which aren't or if no way to tell. Also, when holding in my hand under a bright lamp, I look at the reflection of the lamp bulb on the dry rock. If the bulb gets clearer than before, I judge the shine to have improved. Maybe 90% of what I'm tumbling now are misc. jaspers/cherts, and I don't think there is ever a time when burnish didn't improve the shine.
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pizzano
Cave Dweller
Member since February 2018
Posts: 1,390
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Post by pizzano on Oct 13, 2021 16:48:20 GMT -5
To answer the topic question......since burnishing requires an element of abrasion, I guess it could be possible to otherwise displace a perfectly fine polish on a stone if "burnished" with the wrong compounds or material.....for to long of time.
Based solely on your explanation and process, you shouldn't need to worry. Your process appears to be more of a deep clean step, rather than a true burnish, not much science required to come to that conclusion.
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ingawh
starting to spend too much on rocks
The rock wants to shine, I just help it get there
Member since February 2011
Posts: 194
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Post by ingawh on Oct 14, 2021 13:49:24 GMT -5
Thanks for sharing your process. I'm afraid I long ago abandoned burnishing altogether. Instead, I hand dry and rub each stone after polishing, and that seems to bring up the luster - probably by removing any water scale and micro particles of polish that may have remained. I was interested to read that your rotary polish is a 1000. I would actually consider that to be a pre-polish in rotary. But by the time you get to burnishing, it has likely broken down much finer (especially given your extended run times), and any tiny particles remaining after rinsing would act as a polish. Plus, of course, 7 mohs rocks will put the final polish on each other at that point, as long as there is enough cushioning that they don't smash together - which is what I think was happening to me early on, and why I abandoned burnishing - it actually reduced the shine I had after polish stage. (This was before I got a vibe, and prior to my discovery of quartz aquarium gravel filler, which was the game-changer for me.) Thanks again for the interesting post
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Post by Bob on Oct 15, 2021 12:48:21 GMT -5
ingawh, 1,000 is my last silicon carbide step. I use cerium, tin, aluminum, or chromium oxides for polish. I indeed was sloppy in how I wrote about the polish stage.
4 weeks to a year or more in coarse grind 50-60 1 week in 80 (sometimes skipped for some rocks; this is starting stage for delicate things like glass/obs/feldspars) 1 week in 220 (though many months for aventurine, feldspars larger than apples and some other things) 1 week in 600 1 week in 1,000 1 week in polish 1 1 week in polish 2 3 hours burnish
For tight granites, basalts and a few other rocks that won't polish but I want to keep anyway, I skip the last 3 steps and do a final in 1,200 SC grit as the end. Sometimes I can't tell whether it's improved over 1,000 or not, sometimes it appears to have improved. A second week in 1,000 might have done the same thing but I've never tested/compared. I'm about to put labradorite in this last group.
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Post by knave on Oct 15, 2021 12:55:22 GMT -5
Bob if I recall, Miss Ingawh, soon to be esquire, has successfully polished basalt! Good luck!
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Post by Bob on Oct 15, 2021 13:32:13 GMT -5
Every now and then knave, I'll put an extra tight piece of granite or basalt or gabbro in polish just to see what happens. I was stunned when one piece of at least which I thought was basalt come out great! It's actually one of my favorite black rocks. But that was the only 1 out of maybe 300 tries. If Ingawh has solved it, I've heard that massage parlors would enjoy it if their basalt hot rocks came in a shiner version that might be easier to visibly clean.
Speaking of...I've been very frustrated at the difficulty of finding pure black rocks of decent size to tumble and polish. So many aren't that dark black really, or are fractured even though don't look like it at first, or too soft and get beaten up, etc. I do have some really pure shiny black pieces of what was sold as black jasper, but none larger than a quarter. I've bought a few pieces much larger than that of what is sold as black jasper, but so far not a single piece is pure black w/o some veins or whatever that are visible.
I've seen the reaction of my friends to a rather large pure green rock I have. So I sort of hope to someday on the shelf have a pure black, pure red, pure white, and so forth. I do have what appears to be a pure black piece of obsidian the size of a cantaloupe, but I haven't yet worked up the courage to tackle it.
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Post by knave on Oct 15, 2021 13:54:55 GMT -5
forum.rocktumblinghobby.com/thread/85133/best-method-polishing-basalt-stonesHere's how my basalt came out of the Lot-O-Tumbler. Smoothed it first in rotary, finished it in the vibe. I was working with smaller pieces, but the Lot-O will polish pretty much anything you can fit in it, and I've done some large pieces. You just add more quartz filler if the pieces are larger. The pieces closer to the camera (bottom of the image) were not in focus, and so that polish doesn't pop. The pieces where you can see the reflection of the tree overhead are more indicative of the results. That said, not every piece took the same level of shine. Basalt by Inga Holmquist, on Flickr
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Post by Starguy on Oct 15, 2021 14:09:02 GMT -5
BobI never noticed much of a difference with agate. I still run them for a couple hours in Boraxo. It helps clean out any micro-depressions in the rocks. I’ve had trouble burnishing with garnet, glass and obsidian. They have turned out with tiny little chips in the surface that overall ruin the finish in my eyes. The last burnish run I did with garnet, I used quite a bit of extra plastic pellets. That seemed to cushion them a little more.
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ingawh
starting to spend too much on rocks
The rock wants to shine, I just help it get there
Member since February 2011
Posts: 194
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Post by ingawh on Oct 15, 2021 19:48:09 GMT -5
Thanks for the shout-out, Knave. Lovely to be remembered. :-)
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Post by knave on Oct 16, 2021 8:37:12 GMT -5
Re: black rocks. Have you looked at Shungite from Russia? It’s 99% carbon But the 5G crowd has made it hard to get.
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Post by greig on Oct 16, 2021 9:53:47 GMT -5
My two cents. You use 4x more soap than me. If I start my burnish in the AM, then I intend to stop in the PM. If I start in the PM, then I usually stop in the AM. I have found that burnish takes minimum of 2-3 hours for most stone, but it doesn't hurt to go longer.
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Post by Bob on Oct 16, 2021 13:29:50 GMT -5
Re: black rocks. Have you looked at Shungite from Russia? It’s 99% carbon But the 5G crowd has made it hard to get. Yes, a couple of years ago. But with a reported Mohs of only 4.0, I felt it was too soft to even attempt to tumble. Before anyone mentions jet, it is even softer. Most of the basalt I've tumbled, even the very blackest pieces, I think are only dark grey because they don't look black compared to the black jasper. Since the small black jaspers look so good, I'll eventually find a large piece I think. Oddly, I found in nature a black rock, almost entirely black, sticking out of a road in Oklahoma. Boy was I stunned after washing it and really taking a hard look at it to discover that is is petrified wood. Hope to tumble it soon.
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Post by Bob on Oct 16, 2021 13:32:53 GMT -5
Those are a nice rich black. Most of the basalt I've tried, at least I sure think that it's basalt, has come from the north shore of Lake Superior, or various locations around Puget Sound area including British Columbia. Very few pieces are this black. Where did yours come from if you know?
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ingawh
starting to spend too much on rocks
The rock wants to shine, I just help it get there
Member since February 2011
Posts: 194
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Post by ingawh on Oct 16, 2021 15:51:30 GMT -5
Those are a nice rich black. Most of the basalt I've tried, at least I sure think that it's basalt, has come from the north shore of Lake Superior, or various locations around Puget Sound area including British Columbia. Very few pieces are this black. Where did yours come from if you know? I lived in Western Washington for almost 30 years, so those pieces were most likely from my collecting around the shores of Puget Sound. You're right - I'm not finding that kind of stone here in Sacramento, California. If only I'd known it would be rare and special!
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Post by Bob on Nov 3, 2021 17:50:03 GMT -5
Well, I've had several batches get done recently, and go through burnish. I've increased my burnish time from about 3 hours to 5-8 as a test. The results are encouraging to me and I even had some sodalite, nephrite, and rhodonite come out a bit more shiny than usual.
I often have one piece of questionable material, such as a granite or basalt, that I'm trying to polish and burnish to see how it goes, even though 90% of the time it doesn't work. It's not being put in with touchy stuff like feldspars, glass or those mentioned above, but I mean with tough jaspers and agates. What I've noticed recently is that as I extend the burnish time, if there is a piece in there that just doesn't work, the longer time in there often results in the burnish job deteriorating the other rocks that otherwise would have come out great.
This is sort of the same as saying that if I'm dumb enough to try burnishing a rock that shouldn't be attempted anyway, of course it's going to possibly screw up other things in the process. But I experiment and learn. It's easy to go back to 1,000 or 600 and fix the damage and then finish up the good rocks and take that one oddball to 1,200 and stop there.
I often examine the surface of rocks that won't polish with a 10x lens. Possibly, I'm getting a feel for that look that predicts they won't polish. Doing it by finger feel hasn't worked. But if you really look, you can see the tiny pits. I've often wondered why the surfaces between the tiny pits don't just polish up okay and leave the pits. But that seldom happens. It might work a few times on some rocks. I think if we got good at this, we could take a 10x look at a rock after 600 or 1,000 and predict rather reliably if it will polish.
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