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Author Topic: Some Tumbling Questions  (Read 5898 times)

johnc

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Some Tumbling Questions
« on: December 31, 2008, 09:00:55 AM »
I'm a very newbie tumbler so I have lots of questions which you guys might be able to answer...


How do you know how much grit to put in?

Can you re-use the grit?   If so, is there a way to clean it or separate it from the sludge?

I got some little plastic balls to put in to my tumbler.  Should I only use those during later phases or all the time?  How many do I put in?  The ones I have tried just seem to float.  I wouldnt have thought they would do that much if they are just floating.

Is there an optimal speed for a tumbler?

Am I ok mixing stones together if they have the same moh's hardness scale?  I've currently got petrified wood, agate, opal, and some amethyst.  So far it seems to be going ok.


Thanks in advance for your helpful replies.
John.


Aussie Sapphire

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Re: Some Tumbling Questions
« Reply #1 on: December 31, 2008, 09:52:23 AM »
Gday John,

Calx can probably give you some good tips as well but here are some thoughts to go along with:

Quote
How do you know how much grit to put in?
Trial and error.  But as a guide, start with this:  for a standard 3 pound barrel, try about 4 tables of 80 and 220 grit, maybe a touch more when you get to the 600 and polish.  Adjust to suit your barrel size.

Have a look at this website for some ideas:
http://geology.com/rock-tumbler/rock-tumbler-instructions.shtml

Quote
Can you re-use the grit?
I probably wouldnt reuse the grinding grit but you certainly can reuse polish for a while.  Need to recharge it when it starts to get a bit "weak".

See this website for instructions on this (and other good stuff):
http://silgro.com/RockTumbling/03_MoreAdvice.htm#ReusePolish

Quote
I got some little plastic balls to put in to my tumbler.
Probably not necessary until later stages where you have removed so much material during grinding that you need to add more material to make it back up to the optimal volume.  If you are working with particularly fragile material, maybe consider using them earlier but maybe vibratory tumbler might be better option in this sitution.

If they are floating, maybe look at how much water you are adding.  Try a little less?  Should be up to the level of the rocks but not too much over.  If too much water, the rocks dont work against each other enough.

See the picture from the first website listed above - you can still see rocks sticking out of the water.  The second website suggests filling water to the bottom of the rocks at the top - if you understand what I mean  ;)

Quote
Am I ok mixing stones together
Should be ok if they are similar hardness.  Remember that hardness is not the only issue - sometimes rocks can be similar hardness but different "toughness" or cleavage, etc.  But, again it is trial and error so if what you are doing is working, then keep going with it.

Quote
Is there an optimal speed for a tumbler?
Yes!  But it depends on the size of your tumbler.

Hope this gives you some ideas to start with. 

cheers
Leah
Aussie Sapphire - The Lapidary Warehouse

mehoose

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Re: Some Tumbling Questions
« Reply #2 on: December 31, 2008, 07:37:35 PM »
You're tumbling opal?!!!?!!
Keep em comin!!!

calxoddity

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Re: Some Tumbling Questions
« Reply #3 on: December 31, 2008, 08:19:51 PM »
Opal tumbling is one of the more high-risk things to do.  I've done it with boulder opal, to some success, but straight opal is a little problematic - it's just so soft.

You should skip the coarser grits entirely and go straight to 600 on your first try out.  That way any wastage will be minimised and you'll get a better idea of the wear rate.  Later you might go back to 220 once you know how the opal behaves, but stay well away from the 80 grit!

johnc

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Re: Some Tumbling Questions
« Reply #4 on: December 31, 2008, 10:07:51 PM »

Hmm I think it's called matrix opal.
I better see if it's still there it's been going for a week on 80 grit  :-\

calxoddity

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Re: Some Tumbling Questions
« Reply #5 on: January 01, 2009, 12:42:32 AM »
if by matrix opal you mean combination of opal and ironstone, the you *might* be okay - ironstone is very durable.  You might have recessing of the softer opal though...

mehoose

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Re: Some Tumbling Questions
« Reply #6 on: January 01, 2009, 01:46:50 PM »
I thought the 'matrix' tag was more for the treated(cooked) opal and the Yowah, Koroit and Boulder went under their own name?
Any one enlighten me?

Merryn.
I love the Yowah ;D
Keep em comin!!!

calxoddity

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Re: Some Tumbling Questions
« Reply #7 on: January 01, 2009, 07:24:13 PM »
I quote:
"Matrix opal  - Matrix opal is where the opal occurs as a network of veins or infilling of voids or between grains of the host rock (ferruginous sandstone or ironstone). Matrix comprises precious opaline silica as an infilling of pore spaces in silty claystone or ironstone. It generally shows fine pinfire colour in the natural state.

Andamooka matrix opal may be enhanced by soaking the specimen in a sugar solution and then boiling in acid to deposit carbon in the available pore spaces, resulting in a dark background. "

mehoose

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Re: Some Tumbling Questions
« Reply #8 on: January 01, 2009, 07:37:47 PM »
Enlightened.
Thanks
Keep em comin!!!

johnc

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Re: Some Tumbling Questions
« Reply #9 on: January 08, 2009, 12:12:54 PM »
This stone was sold as yowah opal.
It seems to be tumbling ok so far, but I'm not really sure I know what I'm doing yet.
We have been tumbling for about 2 weeks on 80 grit and everything is quite rounded.  It's hard to know when to stop the first stage.  We decided to give it a bit longer and see what happens.
I guess the worst that can happen is that we end up with a tumbler full of sludge  :)

calxoddity

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Re: Some Tumbling Questions
« Reply #10 on: January 08, 2009, 02:39:50 PM »
John,
  The purpose of the 80 grit it to shape the stone.  Once you're happy with the shape, stop.  The finer grits are supposed to progressively smooth the shape.  For some stone, I've left it in 80 grit for 2 weeks because it hadn't got rid of the rough edges - just check it every couple of days of week 2, as you might need to top up the grit if it's been working hard...

Regards,
Shane

 

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