doit4luv
starting to shine!
Member since September 2004
Posts: 43
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Post by doit4luv on Jan 12, 2005 15:05:59 GMT -5
I am about 5 days into the polish phase using Aluminum oxide on rainbow obsidian. I tumbled it for about ten days in 1000 grit silicon before moving to polish. I checked the stones yesterday and the polish was taking very well on the flat portions of the stones, but the edges were dull and gray and not taking on polish at all. I am using ceramic media during this polish phase which I have been using throughout all of the other cycles. Should I have changed the ceramic media before going to polish? Should I be using the ceramic media at all during this phase? Would plastic pellets have worked better at this point? How can I get the edges to polish? Is this too many questions at once?
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Skipper
spending too much on rocks
Member since March 2003
Posts: 258
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Post by Skipper on Jan 12, 2005 15:15:06 GMT -5
All good questions. Because obsidian is a glass, it feactures and dulls easily. The key is the use of pellets. If ceramic provides cushion (I've never used it), then you should be OK. You need a cusion in all stages after coard grit. Unfortunately, in my experience, once I develop dull edges, I have to take it back to the 600 grit stage and come back through polish. You can use the same cushion media between 1000 and polish no prob.
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James
freely admits to licking rocks
Member since October 2003
Posts: 876
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Post by James on Jan 14, 2005 5:14:50 GMT -5
You need a variety of different size stones in the mix. They contact each other better and aid in the polishing. With that said, I guess ceramic could do the same. I worry though that it ceramic might abrade the softer obsidian, which is most likely the case... Try pellets. I've never had a problem.
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Banjocreek
fully equipped rock polisher
Member since March 2003
Posts: 1,115
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Post by Banjocreek on Jan 14, 2005 10:59:55 GMT -5
I had that problem once and once the edges and corners started getting dull it was beyond hope. It seemed that they were being banged up in the polish because it was just the larger heavier stones that went gray. The smaller lighter stones were fine. My conclusion is that I did not have enough cushioning material. So I had to bring them back to 500 grit 4 days, through 1000 4 days again, and this time put in 1/3 stones and pellets to the 3/4 line. I use Tin Oxide as polish and went 4 days, and all was well. All I can figure is that the bigger pieces were just getting too beat up. The changes I made worked, and I paid close attention not to leave them in polish too long. There's another two cents worth, good luck!!
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Post by creativeminded on Jan 14, 2005 12:27:48 GMT -5
I would use plastic pellets on something that delicate, but I use plastic pellets anyway as a filler. Tami
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doit4luv
starting to shine!
Member since September 2004
Posts: 43
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Post by doit4luv on Jan 14, 2005 20:38:56 GMT -5
Thanks everyone for your suggestions. I have been thinking too, since I made this post, that perhaps I should use the plastic pellets and not the ceramic (which has previously been recommended somewhere for obsidian). Each ONE of you has given me something to change when I do this over again. I also noticed that the smaller pieces did turn out better during the polish stage and it is the larger ones that are rough on the edges. So, back to the drawing board it is...this weekend!
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Post by BearCreekLapidary on Jan 15, 2005 21:17:34 GMT -5
I am a little late in my response ... but I have never used the ceramic media due to the fact that it can abrade the obsidian.
I think you will find the plastic pellets much more favorable.
Thanks for posting the question. Whether you know it or not ... you have just helped who knows how many people. They will read your comment and the related responces and be able to learn from you. Too many times people just don't ask.
Thanks for the question and have a great weekend. Besides that is part of the fun of tumbling ...
John
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