mooresean68
having dreams about rocks
Member since February 2018
Posts: 52
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Post by mooresean68 on Jul 12, 2018 22:29:03 GMT -5
Hi All I could really use some experience and pointers here. A few specs for the tumble: 6bl barrel about 2/3rds full, based on 4 step process 80 SiC, 120-220 SiC, 500 AO 8 days in Cerium Polish Plastic pellets for filler (won't use that again) Slurry seemed ok, maybe a little thin if anything The contents was mixed and I expected some to polish and others not. What I didn't expect is twofold: First it made many of the softer stones worse ie worse than coming out of stage 1 and second there was significant damage (breakage and cracking) All the stones went into polish with the same apparent surface feel and while the agate and quartz came out nicely pretty much everything else came out worse. The images show the amount backwards these stones went. Next to the yellow agate, the other stones were all as smooth to the touch as the agate when they went into polish. Any ideas/experience to this behavior?
Much appreciated thanks!
-Sean
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Post by aDave on Jul 12, 2018 23:51:03 GMT -5
I'll see if I can help, though it looks like you have a few different things going on. I'll preface this by letting you know I am purely a rotary tumbler person, so take my advice with a grain of salt. I'll pick at what you mentioned below. Your stages in terms of grit seem to be pretty good, though you didn't list how long you go for each. For reference, here's what I do: Coarse grind until done. This might be weeks or months. 120/220 10 days. 500 AO 2 weeks. Polish (1:14000) three weeks. That's just me. Not saying it's right or the only way to go, but I've had good, consistent results with my rotary tumblers. That said, I'm not sure it's your tumbling regimen that is causing you problems. It's just something to be noted. I find your comment about plastic pellets to be interesting. I've had tremendous luck with them, and I would never tumble in a rotary (at certain stages) without them. I'd be curious to know why you don't like them. For example, here's a thread about one of my most recent rotary batches. Plastic pellets were used in all stages after the coarse grind: forum.rocktumblinghobby.com/thread/83674/mixed-batch-2018-3I really think it's the rocks you're tumbling instead of the process. Some of it looks to be granite-type, and granite is known to undercut due to the different hardness of the material in each individual stone. What you are often left with is what you are seeing...severely pitted rocks. If you haven't done so, make sure the rocks you're tumbling are near the same hardness. Agates and jaspers around 7 on the Mohs scale (and other similar material) can often be tumbled together without issue. When you start getting into granites and softer stones near 5 on the scale, you'll start running into issues trying to get a polish on them. I think that's what you're dealing with. Get rid of the softer stones, stick to harder stuff, and I think you'll find success at the end of the road. Good luck, and if you have more questions, keep them coming. Regards.
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Post by grumpybill on Jul 13, 2018 9:31:51 GMT -5
I do a fair amount of granite, both pre-forms and pebbles, always with jaspers and/or agates in the same barrel.
My guess is that there wasn't enough cushioning during the polish stage and the stones beat themselves to death. I find it helpful to have every nook and cranny filled with smalls, be it pellets or very small stones during the latter stages. Overfilling the barrel also helps, as does having a fairly thick slurry. Using this method I have no qualms about mixing stones with different hardness...within reason, course. I've run borosilicate glass together with jasper and agate with no deleterious effects.
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doublet83
starting to spend too much on rocks
Member since March 2016
Posts: 118
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Post by doublet83 on Jul 13, 2018 9:58:10 GMT -5
I've had this experience too with softer stones looking worse after polish. I think all the white stuff you see are signs of bruising. This maybe solved if you tumble the stones with a lot of small filler or ceramic media to make the tumble more gentle.
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tkvancil
fully equipped rock polisher
Member since September 2011
Posts: 1,547
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Post by tkvancil on Jul 13, 2018 11:11:04 GMT -5
I have also experienced this. Both rotary and vibratory. It can happen with mixed hardness stones such as granite and many types of feldspar.
I really don't think there is much one can do beyond stabilization that will cure this. Once did a rotary batch that had a goodly amount of local granite. Some came out fine but others looked much like yours. My last vibe run had some feldspars which did this. I run a thick slurry (by means of a thickener) with lots of cushion but still the rocks went bad.
My theory is that the lack of material removal to form a slurry is the culprit. All stages before polish remove material even if only a small amount in the finer grits.
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mooresean68
having dreams about rocks
Member since February 2018
Posts: 52
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Post by mooresean68 on Jul 14, 2018 0:31:50 GMT -5
Great advice everyone thanks! I think I'll try again with much more cushion and thicker slurry. Beyond that it sounds like it can just happen so I'll keep that in mind as well as I experiment. aDave I didn't like the plastic pellets mainly due to my current clean out process. I didn't realize they floated and went every where on me, but seeing your results and that they are small and will fill all the nooks and crannys I may give them another go. One further question around cushion, contents and barrel balance. I did have some larger sized stones in the mix and looking back wonder if those weren't a large part of the damage done. Any suggestions around larger stones at the polish stage? Think 3 or 4 stones of about 3 times the size of the rest of the mix. With something of those sizes is it better to focus polishing the large stones and let the rest just be the aggregate cushion? -Sean
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Post by aDave on Jul 14, 2018 0:50:25 GMT -5
Great advice everyone thanks! I think I'll try again with much more cushion and thicker slurry. Beyond that it sounds like it can just happen so I'll keep that in mind as well as I experiment. aDave I didn't like the plastic pellets mainly due to my current clean out process. I didn't realize they floated and went every where on me, but seeing your results and that they are small and will fill all the nooks and crannys I may give them another go. One further question around cushion, contents and barrel balance. I did have some larger sized stones in the mix and looking back wonder if those weren't a large part of the damage done. Any suggestions around larger stones at the polish stage? Think 3 or 4 stones of about 3 times the size of the rest of the mix. With something of those sizes is it better to focus polishing the large stones and let the rest just be the aggregate cushion? -Sean As far as cleaning out plastic pellets, I have a couple of screened sieves that just let me skim off the pellets. Since they float, the clean up of the pellets should go relativley quick. Dump all of your rocks and pellets into a bucket. All of the pellets should float to the top while the rocks remain at the bottom of your container. From there, screen off your floating pellets, Then rinse the rocks as need be. As to your other question, what size barrel are you tumbling with and what is the composition of the barrel? W
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mooresean68
having dreams about rocks
Member since February 2018
Posts: 52
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Post by mooresean68 on Jul 14, 2018 0:57:41 GMT -5
aDave I'll try and get some pictures tomorrow of the composition of stones I ran; the barrel I've got both a 12lb and twin 6lb barrels on a lortone qt66/12. Heh I suppose a 2 dollar goldfish net ought to be handier than trying to scoop the pellets out by hand.
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surreality
starting to spend too much on rocks
is picking up too many rocks at the beach again
Member since January 2012
Posts: 217
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Post by surreality on Jul 14, 2018 1:39:40 GMT -5
Do you have any of the bucket screens? This kind (suggest using the affiliate link on the forum to find them through there): www.amazon.com/gp/product/B00C7YCQIQ are what I mean. I finally found the sanity-saving way to handle this with one of these; set it over my slatted outdoor table (they fit into the top of a 5 gallon bucket very well also, it just never runs the risk of overflowing with my cheap outdoor table) and then just plunge the hose into the barrel to rinse. It will raise all the pellets up to the surface and overflow, and the bucket screen catches the pellets. It also rinses off a fair bit of the slurry in the process. Once the pellets all float off and are caught in the screen, you can lift the bucket off of the screen and hose it off on the outside, since some of those little buggers will stick. You can let the pellets dry out a little in the screen while further rinsing out your rocks; when damp they want to stick to absolutely everything. I scooped out handfuls to dump in a tiny bucket and let the rest dry on the screen until I can flick them off into the bucket. The screens are super useful for rinsing rocks as well; we have a stack of them around. We use them for seashell sifting and similar, too.
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Post by fernwood on Jul 14, 2018 4:50:11 GMT -5
I add clay kitty litter to all stages but final polish. Works great for thickening the slurry. I also save used slurry from all but polish. reuse that and mix with new grit.
Many use tile spacers as filler. Some even use leather pieces.
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mooresean68
having dreams about rocks
Member since February 2018
Posts: 52
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Post by mooresean68 on Jul 14, 2018 10:30:25 GMT -5
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surreality
starting to spend too much on rocks
is picking up too many rocks at the beach again
Member since January 2012
Posts: 217
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Post by surreality on Jul 14, 2018 12:35:12 GMT -5
I swear by those things. Mine are from somewhere else, but I try to find the amazon ones for the forum funds and whatnot. (And I'm going to be order the set of five through there later in the week myself, we could use some more of them.) They really are a sanity saver. The husband plans on setting up one of the bigger buckets to drill drain in the bottom to use as a makeshift outdoor sink once there's one of those on top.
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mooresean68
having dreams about rocks
Member since February 2018
Posts: 52
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Post by mooresean68 on Jul 16, 2018 10:03:57 GMT -5
aDave well looking at the image of the stones, I can see I'm missing smaller bits. The barrel size is 6lb
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Post by rmf on Jul 16, 2018 14:06:08 GMT -5
mooresean68 Your problem may not be with the "recipe" but with your tumbling barrel and the type of rocks being tumbled. It has been my experience that a rock tumbler like a Lortone 3A you can tumble a much wider variety of rocks together without issue. But when you go to the 6# an 12# tumbler drums the increase in diameter causes the rocks to "fall" further. This acts like someone stiiting there with a hammer and pecking away on the softer stones. The is easy to observe when tumbling Agates mixed with quartz and quartzites. Even though the rocks are all hardness of 7 on mohs scale they are not all the same toughness. Agates, due to their microscopic fibers of quartz (cryptocrystaline) act like a cable and impact force is transmitted and diffused alone the fibers. Where as quartz and quartzites are more granular and tend to chip around the edges leaving a frosted look. The images you included look like they are much softer than the agate. If you tumble rock by hardness groups you will have better results.
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