rockingcatlady
off to a rocking start
Member since January 2021
Posts: 5
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Post by rockingcatlady on Feb 26, 2021 22:58:48 GMT -5
Hi everyone, I've been holding off on posting again until I had something to share, and I've run into a problem I thought you all could help me out with! I was given a National Geographic tumbler a few months back, and was puzzled by the lack of a shine on the first batch I did. The research I did made it sound like this is a known problem, and that it's more of a matte finish than a gloss. Overall, I do like how this batch looked. Some of the rocks are a bit shinier than others (the round green one I experimented with a bit of polyurethane I had on hand just to see what it did after reading about it being a potential shortcut), and not are all completely smooth. I'm an artist, though, so the dings, blemishes, cracks and all that aren't a problem for me.
It's the second batch, which I just finished with yesterday that I'm not certain about. I purchased aluminum oxide for use in the final polish from a website I found recommended on this forum several years ago. In comparison the first batch, the second batch look like... well, rocks. They came in a package with no indication of what minerals they are, or the mohs hardness rating of them, which I'm sure could be a contributing factor. Again, the imperfections in the stones are a plus for me, so that's not the issue. My question is why they look so much less smooth than the first batch, and also appear a little cloudy. It doesn't have the matte look of the grit from the National Geographic kit, and it almost looks like the pre-polish got scraped off somehow.
Do I need to go back to the pre-polishing stage, maybe try a different technique? I currently only have the one tumbler, though I'm looking into getting a second just so I can speed things up a bit and have more than one batch going, in case I run into more problems as I learn the ropes.
Any advice would be welcome, thanks for reading.
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saxplayer
fully equipped rock polisher
Member since March 2018
Posts: 1,327
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Post by saxplayer on Feb 26, 2021 23:39:18 GMT -5
Hi there!
If I can make a few suggestions it may be helpful.
To me - the most important 2 (maybe 3) things to getting a good shine are:
1. Start with decent known hardness material. This is usually agate or jasper in the mohs range of 6.5.7.0 if possible. Most agate you can buy from therockshed.com is a great place to start. If your material is different hardness, you won't get shaping and you won't get polishing.
2. Start with good quality grit or you just waste time. I recommend therockshed.com again for good quality grit source. I would get a decent rough grit for stage 1, then sic 500 and aluminum oxide polish etc all from them. If your previous stages don't "prepare" the rocks for a polish stage - they won't polish. It looks like to me the 2nd batch you ran has this problem.
(3). Have fun, plenty of patience and inquisition to learn. You have proven the last part by being here, asking questions. We will try to help you out, but it takes time!
My advice from what I can see from your photos:
Besides the above, the 2nd batch looks like too random a mix of stones. You need to have similar stone to start with. I also question the grit you are using, try and get the 3-4 stages of grits and polishes from one source as per above. Maybe buy 5-10 lb of material (agates or jaspers) from therockshed.com along with grits, and report back here in 6-8 weeks and lets see how it went. Do be patient on stage 1 as the shaping is all you will get from stage 1 - moving on after that is for preparation for polish and not shaping any longer.
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standles
spending too much on rocks
Well all I got was a rock ... Cool!
Member since February 2021
Posts: 325
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Post by standles on Feb 27, 2021 8:36:12 GMT -5
I think the difference you are seeing on the second batch is it looks like they left the first stage too early. There are still cracks, pits, porosity and imperfections in them. Stage 1 is where you get rid of all that. Coming out of stage 1 they should be smooth (not shiny) and no imperfections. The issue is even if you are "burnishing" (washing) them between grits that grit gets trapped in those imperfections and contaminates the next stage. If you want to move them forward with the imperfections for artistic purposes then cleaning them with a toothbrush or water pik to eliminate the prior grit is needed.
If I am pushing for a perfect batch... I go so far as to inspect each rock after stage 1 with a lighted magnifier looking for imperfections. If found back they go for more tumbling.
Another thing that may be going on is because of the imperfections the final polish may be getting into the small pits and cracks causing that white haze or frosting. I had some in batch that had fine cracks on surface. You could not feel them but that AO polish sure found them.
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rockingcatlady
off to a rocking start
Member since January 2021
Posts: 5
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Post by rockingcatlady on Feb 28, 2021 18:53:25 GMT -5
First off, thank you both for the feedback, I appreciate it. I also question the grit you are using, try and get the 3-4 stages of grits and polishes from one source as per above. With the exception of stage 4, it's the same grit as my first batch, hence my confusion. Maybe it's simply that it wasn't given enough time in the first couple of stages, or grit wasn't completely washed out between steps. I'm currently running step 1 on a batch that isn't an assortment, but is just agate and jasper just to see if I can duplicate the problem, or if it's something else entirely with the random bag I was given. Since there's no information included with it, I'm sure it's just one of those things. I do feel kind of guilty since it was part of a gift, and it's lousy hearing it's not great quality. I'll likely have a much better grasp on things in late March or early April, when I have three different batches to compare. I think the difference you are seeing on the second batch is it looks like they left the first stage too early. There are still cracks, pits, porosity and imperfections in them. Stage 1 is where you get rid of all that. Coming out of stage 1 they should be smooth (not shiny) and no imperfections. The issue is even if you are "burnishing" (washing) them between grits that grit gets trapped in those imperfections and contaminates the next stage. If you want to move them forward with the imperfections for artistic purposes then cleaning them with a toothbrush or water pik to eliminate the prior grit is needed. If I am pushing for a perfect batch... I go so far as to inspect each rock after stage 1 with a lighted magnifier looking for imperfections. If found back they go for more tumbling. Another thing that may be going on is because of the imperfections the final polish may be getting into the small pits and cracks causing that white haze or frosting. I had some in batch that had fine cracks on surface. You could not feel them but that AO polish sure found them. I'll probably be looking into a different kind of grit in the future depending on how the batch I'm currently running ends up looking. It's starting to warm up where I am, so I won't need to continue only rising them out with buckets instead of not using a hose for much longer, so hopefully I can really get them cleaned out. I keep a handful of toothbrushes on hand for painting, so I'll just use one of the ones that hasn't been used before to make sure I completely clean them out before I throw them back in the tumbler. Once I return to working on my second batch, I'll post an update to show if things have improved, or if I've ended up in the same position as before. Right now, from what you've both told me, I'm suspecting that the problem is with the polish grit getting inside the pores of all of the stones.
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rockingcatlady
off to a rocking start
Member since January 2021
Posts: 5
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Post by rockingcatlady on Apr 24, 2021 19:35:52 GMT -5
Hi folks, it's been a lot longer than I meant for it to be, but after trying to run through the second bath a couple more times, nothing really change, they've all still remained cloudy, so I'm chalking this up to a loss and inexperience.
I did a third batch using stones of all hardness level and they turned out completely fine.
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