moggymiaow
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Post by moggymiaow on Aug 12, 2013 21:06:07 GMT -5
can anyone help with instructions on tumble polishing kauri gum, as it is soft what grade grit should I start with?
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The Dad_Ohs
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Post by The Dad_Ohs on Aug 12, 2013 21:36:31 GMT -5
I think you will need to be a little more specific on this material. I, for one have never heard of it, but that's not surprising to me, I am still learning too. A couple questions which others will ask so I will give you a heads up and you can post answers here so other can help you more easily.... What is the mohs hardness of this material? Are you going to use a rotary or vibe Tumbler? or both? How big is it? How much of it are you tumbling? If just one piece you will need other rock to add to it but it has to be about the same hardness or it will be ruined/destroyed during tumbling. Have you tried looking it up on the net?? I only ask this because while we have a pretty broad base of knowledge here with these wonderful people, there is a chance it is known under another name. Can you post a picture of it, to help other see what you are working with? Pictures always help! If you can answer these we can probably help you. I would suggest answering these now, so others who see the thread have more to go by before they answer. Good Luck !! just found this as an insight into Kauri Gum, good reading.... en.wikipedia.org/wiki/Kauri_gumThis tells me you are working a petrified resin similar to copal and amber. this are very light and under no circumstance should be tumbled with any course grits or they will disappear on you. I would think vibe tumble with nothing rougher than 500-600 grit, maybe go straight to 1000grit and see if that works, if not go backwards 1 grit and try it and check it twice a day to make sure it isn't wearing away too quickly... but then thats just me, I guess polish as normal. Remember this you can't add material back if you go too course, I would ere on the side of caution and try the 100 grit first then go back to 500-600 if you don't get the right results within a day or 2.... but thats just my take on it after 10 minutes reading.. others have more knowledge than I do!!!
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moggymiaow
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Post by moggymiaow on Aug 12, 2013 22:25:06 GMT -5
thanks, yes you are right kauri gum is similar to amber (It is New Zealand's equivalent), however the smell is very different. Amber smells like pine, kauri smells like paraffin/kerosine. I have around 1/2kg to polish. two pieces will need to be broken up before tumbling as they are far too big for my little rotary tumbler. I haven't used my tumbler for a couple of years, we used to live next to a beach where you could pick up loads of agates and other stones for tumbling, here we only have sand. I have three grades of grit (I cannot recall the numbers off the top of my head, I will have to wander out to my shed) and a pre polish and a polish. In the past with the agates I tended just to use the coarse grit and let it gradually turn into medium grit, then the fine, and polish. I am no expert, I only tumbled maybe 10 lots at the absolute maximum.
So from your reply I take, start with the finest grit (ie not the pre polish or polish) and see what happens, check daily. I might keep the best bit out for the first day in case things go pear shaped.
Yes I did try looking it up on the net (it is how I found this site), but I can only find instructions for hand polishing, which I have already done with amber anyway.
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The Dad_Ohs
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Post by The Dad_Ohs on Aug 12, 2013 22:31:50 GMT -5
if you are using a rotary tumbler, I would suggest trying your pre-polish first and see what happens after a day of tumbling and make sure you have lots of cushion material.... ceramic media.... so it is not banging into itself all the time which will cause more problems like cracking or breaking. I think you would be best served with a vibe for this material, but, with enough care, you should be able to use a rotary tumbler. I have a feeling that that stuff is soft enough that you could do it with sand paper and have it come out nice... it is probably that soft!!
Start with your pre-polish and see what happens, then go rougher if you have to, but keep an eye on it,, it will wear down very quickly in course grit. do not go below 500-600 grit and even with that check it frequently to minimize loss of material from tumbling... and post pics!!!!
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moggymiaow
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Post by moggymiaow on Aug 12, 2013 22:41:02 GMT -5
how to you insert pics to this forum? I have resized until it is only 66kb, but it tells me it is still too big. Any smaller you won't be able to see what I am trying to show
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moggymiaow
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Post by moggymiaow on Aug 12, 2013 22:47:45 GMT -5
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moggymiaow
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Post by moggymiaow on Aug 12, 2013 22:50:37 GMT -5
the largest piece is the poorest quality and will get broken up before trying to polish. The smallest looks the best quality, though not wonderful.
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Deleted
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Post by Deleted on Aug 13, 2013 5:15:43 GMT -5
Greetings [moggymiaow], firstly may i welcome you to RTH Forums, please check out my Sticky's below. #2 gives the forum BBCode in the V4 format that still works in V5. #3 will help you workout the hardness. #4 will tell you what grits to use especially for softer rocks. kauri gum 66.62 KB (68,223 bytes) -- Please click images to open larger images in a new Tab, same with everything that is Underlined! I hail from (The Barony of Seabegs) Bonnybridge, Stirlingshire, U.K, where aliens (15mb) sometimes come for a visit & about 4 miles west from this monstrosity! Sticky's: their contents are resource information 1#: Vendors worldwide (2mb), 2#: How to use the forum, 3#: How to identify rocks & minerals, 4#: Save money on expensive grits & polishes, 5#: Aussie Lapidary Forum: Rock Tumbling Guide!
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Deleted
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Post by Deleted on Aug 13, 2013 18:29:49 GMT -5
personally I would hand polish those.
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gemfeller
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Post by gemfeller on Aug 13, 2013 21:42:27 GMT -5
I agree with Shotgunner. I've never polished Kauri Gum but I've polished a lot of amber (Baltic and Dominican.) Kauri Gum (Copal) isn't fossilized like amber and can be tricky stuff -- so is some amber when you get it too warm on the sanding or polishing wheel!
Copal isn't hard to polish but the techniques are very different than for silicates like agate/chalcedony/agate. Mostly it's done by scraping to shape with a steel blade and sanding by hand, followed by polishing with a cotton cloth. It's not really a gem material like amber. It was used as chewing gum in earlier times and its biggest use is as a base for making varnish when mixed with linseed oil.
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moggymiaow
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Post by moggymiaow on Aug 14, 2013 0:09:24 GMT -5
Looking and feeling it, the hardness seems similar to amber. I am happy to risk the large poor quality lump in an experiment. I don't fancy polishing it all by hand as the smell is very unpleasant.
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Deleted
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Post by Deleted on Aug 14, 2013 0:14:49 GMT -5
to deal with the smell, you must chew a very pungent and flavorful bubblegum............ I am in the USA and this is my choice of bubblegum! Tumbling is a way to polish many stones slowly. You have only three stones to polish. You will be done in three hours by hand.
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