Larry
spending too much on rocks
Member since June 2008
Posts: 267
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Post by Larry on Jul 5, 2008 9:46:18 GMT -5
Well, I just emptied my second tumble (beach rocks) just now and noticed there was a white film on most of the rocks in that tumble. I sued Borax overnight so I know it's not the Aluminum Oxide still on the rocks. They are pretty shiny, just the color is muted a bit. If you wet them, they look much better.
Some of these were ones from my first tumble that I had this issue with so put them in polish again, so I know polishing longer doesn't help.
In my first tumle, everything that was light or whitish in color shined up nice and the reds and greens had the film. This batch was all reds and greens and most have a film.
Is this a known thing with some things that can be tried to save them? Or is this a case where I can redo as much as I want and won't get anywhere? I have a feeling that these rocks just will not polish with their true wet color.
Thanks in advance for any help or ideas. It's kind of a downer getting such poor results as it kinda kills the anticipation for future tumbles.
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rallyrocks
fully equipped rock polisher
Member since November 2005
Posts: 1,507
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Post by rallyrocks on Jul 5, 2008 10:49:00 GMT -5
First, a couple of questions- you refer to this as a "film" is it something that can be wiped off? or once they dry again to they get hazy?
Are these red and green rocks really solid, or might they be a little bit porous? you can test this by putting a drop of water on one- does the drop just sit there on the surface? or does it seem to soak in?
Being early batches in your tumbling experience curve, my guess would be either 1) they are not good polish-able stones- sandstones, limestones and many other types of stone simply do not have the solid structure needed to obtain a polish- or 2) one of the previous steps was not run long enough and you are suffering from very fine scratches that the polish stage can't smooth over.
My suggestion would be to back them up to a pre-polish- either a 500-600 SiC or 1000 AlOx, run them for a week or so at that stage then trying polish again.
First few batches are learning experiences for all of us, so don't let it get you down, just keep trying...
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Post by Toad on Jul 5, 2008 11:44:39 GMT -5
I agree, if the rocks aren't porous, then you probably need to go back a step or two to grind a bit longer.
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huffstuff
fully equipped rock polisher
Member since August 2007
Posts: 1,222
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Post by huffstuff on Jul 5, 2008 12:06:41 GMT -5
Hi Larry,
I had a problem with my last batch, but only with tiger eye. I did a 2-day (I know, a lot) final borax burnish after I was finished all of my stages, and all of the tiger eye turned out cloudy, like a film that didn't wipe off, and the edges were particularly bad. I did a little hand-polishing with some more AO which helped a bit. I put them in polish with this next batch, and they are much better. They didn't like to finish in borax. All of the other rocks (a variety) were fine with the borax.
So maybe try some AO on a damp cloth and rub hard. Or if you go back a step or two, check them right after final polish, before the borax, and see how they look.
Funny typo in your post - I thought you were saying you sued Borax!
Good luck.
Amy
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Larry
spending too much on rocks
Member since June 2008
Posts: 267
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Post by Larry on Jul 5, 2008 15:26:49 GMT -5
Thank you all for the responses. A few answers to your questions... I tried putting a bead of water on and it just sat there. I'm not too big on the geology stuff yet but these rocks are smoother and look great when wet versus the really porous sandstone type stuff littering the beach. The white film was seen after polish and before borax but still there after overnight borax wash. When you wash the rock by hand, it looks great then back to the white film when it dries. I'm starting to think it's the makeup of the rock. The ones that do shine up nice have a very smooth feel to them but these ones feel a little more rough. Maybe my issue was that I started them in fine since they were rounded beach rocks and didn't do any coarse grit. Maybe I do need at least a half coarse stage to get scratches I can't see out of these particular type rocks. I don't want them in coarse too long as they are already small enough and I don't want them to vanish. For reference, if my rocks come out of prepolish with a white film, should I be pretty sure they will end up that way after polish? Would rather go back at that point than waste time trying to polish a losing effort. And huffstuff... was a funny typo. Would be sad if I got THAT worked up over it  |
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Post by johnjsgems on Jul 5, 2008 22:28:04 GMT -5
If you started in fine you probably need to run a 120/220 or 220 step followed by fine (500F or 600). Some places have really hard water and you need to use distilled water with the polish, If only some batches come out hazy that probably isn't it.
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Post by Toad on Jul 6, 2008 6:36:21 GMT -5
No mater how smooth the rocks are to begin, I would always start coarse then move to 220, 600, pre-polish and polish. Never had a white film. Never hurts to go back further than necessary, all it does is shrink the rocks a little bit. But if you don't go back far enough, you'll never get a good finish.
That said, if your beach rocks vary in composition/hardness (either between stones or within each stone) they will beat each other up and you won't get a good finish either.
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Post by LCARS on Jul 6, 2008 13:36:17 GMT -5
Sounds like it could be crazing a.k.a. bruising.
This happens when rocks impact each other in the tumbler and damage the surface finish. If this were the case I would recommmend taking them back to 500-1000 grit prepolish using a slurry thickener and some cushioning media like plastic pellets.
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Larry
spending too much on rocks
Member since June 2008
Posts: 267
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Post by Larry on Jul 6, 2008 20:28:21 GMT -5
Thanks again everybody for the help.
I think my first change will be to run everything through coarse first. I was thinking about not needing the shaping but was forgetting about removing scratches. After I give that a try, I will know for sure since I have a bunch of the same green type rocks.
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