jerime2
off to a rocking start
Member since October 2008
Posts: 2 
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Post by jerime2 on Oct 28, 2008 21:12:34 GMT -5
Hi all;
I'm new to rock polishing and am working on some fractured but nice-looking banded andesite, with a Thumler Ultra-vibe 18.
I started with 120-220 silicon carbide grit and initially the paste felt "gritty" or a little sandpapery when I rubbed it between my fingers. After about 36 hours the mud felt smooth or "clayey" so I rinsed everything well (loved the progress I'd made when I looked at the rocks) and started over with a new load of the same grit. Now after another 24 hours the grit again feels clayey but I've still got a few pits in the rocks and want to keep going before I switch to a finer grit size. My question is whether the "clayey" feel is the right indicator of when to change grit, or if I should continue to run longer than 1 to 1-1/2 days without replacing the grit?
The andesite is very fine-grained but not quite crypto-crystalline, if that helps.
Thanks in advance for any guidance.
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Post by connrock on Oct 31, 2008 4:38:33 GMT -5
Jerime,
What you're experiencing is normal.
In a vibe the grit will break down in 1/2 in about 12 hours.In other words if you're using 120 grit it will break down to 240 grit in 12 hours.
In a rotary the grit takes 7-10 days to do the same thing!
The only indicator of when to go to the next grit after roughing is not the feel of the grit but rather when you are satisfied with how the rocks look!
The rough course is the root system of the tumbling tree.If the roots are poor the tree will also be poor!
Those pits you have won't disappear during the rest of the cycle but rather WILL cause you problems down the line and after all that work and time you will end up with polished junk!
If you notice that on this board the people who have the best looking rocks also take the longest time to rough them in!Another point is that they start out with quality material.
Only YOU can decide when the rocks move on to the next step!
connrock
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Post by Hard Rock Cafe on Oct 31, 2008 6:51:30 GMT -5
I agree with Connrock (one of my mentors). I also use a UV-18 and move on to the next stage after 24 hours. But, I use a rotary in the coarse stage to take out all of the imperfections.
Tumbling until all the pits are out can leave you with a much smaller stone. You might try grinding the pits out and then tumbling them. I haven't done this yet myself; I've just been putting my pitted rocks aside for a future project to grind them all.
If new pits are revealed during tumbling, then you may be in for a lot of frustration.
Chuck
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chassroc
Cave Dweller 
Rocks are abundant when you have rocktumblinghobby pals
Member since January 2005
Posts: 3,586
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Post by chassroc on Oct 31, 2008 7:48:26 GMT -5
I do not vibe, but grit should break down progressively in any tumbler. Pits are a big problem for most of us. If your material has a lot of pitting, you introduce new pits as the rock is tumbled! You can try getting the imperfecrions out with a dremel or a grinding wheel but it gets boring with a whole load of material. Most of us run a rotary with material for a longer time(weeks not days) for the first stage.
csroc
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morticiamonroe
starting to spend too much on rocks
Member since October 2008
Posts: 147
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Post by morticiamonroe on Nov 2, 2008 15:13:35 GMT -5
The rough course is the root system of the tumbling tree.If the roots are poor the tree will also be poor! Those pits you have won't disappear during the rest of the cycle but rather WILL cause you problems down the line and after all that work and time you will end up with polished junk. If you notice that on this board the people who have the best looking rocks also take the longest time to rough them in!Another point is that they start out with quality material. Only YOU can decide when the rocks move on to the next step! Thia makes perfect sense. Thanks for the advice. |
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docharber
has rocks in the head
Member since October 2008
Posts: 716
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Post by docharber on Nov 2, 2008 21:54:09 GMT -5
One other thing- f you resign yourself too accept some pitting, or unpolished depressions in your stones, make sure they don't contaminate the next cycle with trapped courser grit- that can ruin your load and take you back at least a step. Scrub the pitted stones to remove every trace of trapped grit before moving on. And if you don't have one, get a separate bowl for polishing to eliminate possible scratches from retained grit in the bowl. Good luck!
Mark H.
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jerime2
off to a rocking start
Member since October 2008
Posts: 2
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Post by jerime2 on Nov 3, 2008 21:32:19 GMT -5
OK, thanks for the responses. Here's an update:
I went thru 3 cycles of the coarse grit, running anywhere from 1-1/2 days to 4 days on each. At the end of the longest run the mud felt creamy, rather than gritty or clayey - I think that told me the grit was still cutting even after it no longer felt "gritty". So now I'm on my first batch of #500, and again I'm wondering when it is "used up" and I need to rinse and replace with the same grit size. If it does break down to 50% in 12 hours, does that mean I'm past the point of diminishing returns in 24 hours?, 36?, 48? or when?
I did get the pit-free surface I wanted on most of the stones after 7 days, but wonder if I could have gotten there quicker, or more cost effectively if I had replaced the grit sooner, or alternatively hung-in with each grit batch longer.
Thanks in advance for any comments.
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Post by connrock on Nov 4, 2008 4:38:24 GMT -5
In each step of the tumbling process a specific grit is used for a specific stage. In the rough stage you want rough grit.After 24 hrs that rough grit is no longer rough but it will continue to grind away at a MUCH slower pace. The efficiency in time is lost when the grit runs for long periods. Try this...... Take a small amount of the slurry and put it in a paper cup.Keep rinsing it and pouring off the slurry VERY slowly until you have only grit at the bottom of the cup. Compare that grit with fresh rough grit. This will tell you a LOT about how grit breaks down and if you should go on to the next step. This will not be of much use with the finer grits unless you use a 10X loupe or microscope as the grit is very fine to start out with. Nothing you are doing is abnormal nor are your questions.I did EXACTLY the same years ago and being self taught without any web to consult I learned the hard way. I spend more time in this section of the site then any other just to try to help people such as you who are still fumbling at tumbling!  ;D It brings back a LOT of memories both good and bad. If you can believe that it took me almost 1-1/2 years to finally get my first so so polish on my rocks.I was happy but not satisfied until I got that "wet" look a long time later. The web and especially this site is a God send for all of us. connrock |
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;D It brings back a LOT of memories both good and bad.
