redwings1
starting to shine!
Member since July 2009
Posts: 45
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Post by redwings1 on Jul 18, 2009 9:24:36 GMT -5
I did a search here but it didn't seem to turn up anything on this condition. I'm new to vibes and I'm getting only what I can describe as a 'frosting' condition (smooth yet sparkley when dry) on my 1st batch of petoskeys in for polish (cerium ox - pink). From research on here I realize that I maybe should not have skipped the 'pre-polish' step between the #600 and polish but I believe that there might be something else wrong with what I'm doing. I am using plastic pellets for cushion and the action in vibe is good. I also did a search for threads on someone specifically polishing petoskeys but came up empty. Its almost as if the polish is reacting with the calcite in the fossils maybe? Has anyone heard of such a thing? I'm reallly concerned about ruining these...they are small already and some were my grandfathers...this has proved to not be as easy as it would seem...thanks for any help!
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Post by frane on Jul 18, 2009 9:29:50 GMT -5
Hi Redwings1,
I am not sure if I am going to be much of any help but I have heard that petoskeys are very soft. I have seen it recommended to do them by hand with finer and finer sand paper. You may want to do a really fine sand paper and then put the cerium on a felt pad and work them by hand. If all else fails, Carnuba wax and buff it off.
Fran
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redwings1
starting to shine!
Member since July 2009
Posts: 45
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Post by redwings1 on Jul 18, 2009 10:03:52 GMT -5
Thanks Fran...and I may have to resort to finishing em up manually. I was really hoping to figure it out in the machine though, as I have a couple hundred of them! Oh well, I'm in no hurry. I really hope that what I'm seeing on there is not fractures but I'm afraid they probably are.
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Post by johnjsgems on Jul 19, 2009 9:55:10 GMT -5
Those are too soft for cerium. You could try a good grade (under .5 micron) aluminum oxide.
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redwings1
starting to shine!
Member since July 2009
Posts: 45
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Post by redwings1 on Jul 19, 2009 11:58:47 GMT -5
Thanks John...and I suppose I'll have to send em back to the 600
first...
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Sabre52
Cave Dweller 
Me and my gal, Rosie
Member since August 2005
Posts: 20,497
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Post by Sabre52 on Jul 19, 2009 18:49:58 GMT -5
Yeah, I'd venture that they are a bit soft for tumbling period. Just the gentle knocking together of the tumbling action is probably enough to cause the frosting which is probably tiny impact craters....Mel
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Post by connrock on Jul 22, 2009 7:06:35 GMT -5
I don't think you will have much success using a vibe here.It's just way too aggressive for a soft stone like that.
I got this off a web site some time ago and have never tried it as I don't have any petosky stones but it may be worth a shot,,,,,
How to tumble Petosky Stones
Step 1: Start with 320 or 500 & finer silicon carbide grit, using a
thickening or suspending agent like syrup, sugar, or molasses for
cushioning.
Step 2: Use 600 or 800 & finer silicon carbide grit with a ratio of 1 to 1 or
2 to 1 of media to Petoskey stones. Use plastic pellets or coarse-ground
walnut shell for media. You may also need to use a thickening agent like
syrup, molasses, or sugar (being careful not to thicken load excessively).
If you use 600 silicon carbide grit, follow with 600 aluminum oxide as a
pre-polish, jumping to the final polishing stage.
Final Step: Use cerium oxide or 0.5 to 0.8 micron aluminum oxide polish,
cushioning with fine-ground walnut shell and a thickening agent like
syrup, molasses, or sugar, but do not thicken load excessively.
connrock
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Post by johnjsgems on Jul 22, 2009 10:37:53 GMT -5
connrock, are those rotary instructions? I've heard of using syrups in rotaries but never in vibes.
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firewalker45
freely admits to licking rocks
Member since August 2006
Posts: 929
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Post by firewalker45 on Jul 22, 2009 16:03:26 GMT -5
Hi Redwings1 and welcome to the board. Petosky stones are a bugger to polish in a tumbler. I have tried a couple of times without much success. Every thing seems fine up to the polish stage. Stage 1. use 220 or 320 grit and tumble until smooth. Stage 2. use 600 grit. In this stage it is important to use a cushioning agent ie (plastic pellets, ground walnet shell(course}. Use in a ratio of 1 to 1 up to 2to 1 cushioning agent to Petosky stone. Stage 3. Use 1000 grit or suitable prepolish. Use the same ratio as step 2 and use new pellets or ground walnut shell(fine). Stage 4 Polish. I know one of the mistakes I made in this stage; is I did not let it run long enough. I stoped after about 48 hours. I hope this helps! BTW if needed, I could let you have some 1000 grit and or some course and fine ground walnut shell to do a batch. Daniel
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redwings1
starting to shine!
Member since July 2009
Posts: 45
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Post by redwings1 on Jul 22, 2009 19:44:50 GMT -5
connrock and firewalker...these both look like sound advice. I'm more optimistic now after reading these good ideas. I'm going to experiment again in the vibe and I know what I'd like to try next (too many small ones to finish by hand!) Daniel, that would be great if you would like to part with any materials you think would help me. This will be a great skill if I can get it down. Fortunately I have a fair amount of soft 'charlevoixs' to practice with. This walnut media...after it has run wet, can it be reused? You guys are a great help
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jpits54
off to a rocking start
Member since May 2009
Posts: 10
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Post by jpits54 on Jul 23, 2009 12:03:15 GMT -5
The only way I've been able to get these polished is by hand. I'm doing up a bag of them right now. I use automotive 325, 600, 1000 grit wet/dry sandpaper and then polish with automotive polishing compound. Definitely gives your hands a work out. I'm thinking there has to be an inexpensive pneumatic sander I could use ... Good luck.
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redwings1
starting to shine!
Member since July 2009
Posts: 45
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Post by redwings1 on Jul 23, 2009 20:13:31 GMT -5
yep, thats the only luck I've had so far too, by hand like how you did it  |
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Post by connrock on Jul 24, 2009 8:27:06 GMT -5
j'gems,
Yes they are for a rotary.
connrock
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