Joined: Tue Feb 05, 2008 10:18 pm Posts: 285 Location: Las Vegas
Quote:
My son has borrowed all my faceting gear but I can't just do nothing. I bought some Lambina opal rough and I'm working it with sandpaper over felt. There's some scratching issues that really don't go away. I went 100grit, 180, 320, 600, then 1500. Final was Raybright A, the only polish in the shop. Then, because of a few scratches, I did it again and slower starting at 300. Then I did it again, starting at 180. Then I did the 600 step for like forever. Still some scratches. Last, I went with 400 straight to polish and it was OK but clearly unacceptable compared to any faceted stone polish I've ever done.
At this point, I think it's something to do with the nature of the rough. Perhaps differential hardness, I dunno.
I've done a dozen opals at this point, most are polished as well as anything. But yesterday, I revisited the first stone, the one detailed above in order to make it nice. Well, it won't cooperate. I am certain that this stone has some physical issue that makes it different. There is no way to sand out the scratches. It just generates more scratches, even at 400 and 600 grit.
Too bad I got this bad apple first, I'd have saved hours.
Joined: Tue Feb 05, 2008 10:18 pm Posts: 285 Location: Las Vegas
gsellis wrote:
Are you sure you are not pulling sand out of a pocket you are contacting? Just a little pit that is hiding?
This is unlikely. This opal is free of blemishes and my protocol is pretty clean, at least it becomes so when I encounter any problems. But thanks for responding.
Joined: Sat Nov 10, 2007 12:14 am Posts: 57 Location: Canberra / Siem Reap
hi- i have always had this problem when trying to finish with anything but cerium or lapsa ( 50,000 mesh cerium).
i go to 1200 on nova- then polish with lapsa.
Joined: Wed Apr 26, 2006 12:44 am Posts: 2056 Location: San Francisco
what brand laps are you using and in what sequence?
If all else fails, dop it and use wet 600 / 800 /1200 / 2400 sandpaper then finish with leather chamois wet w/ CeO. That's the hand powered way of doing it.. and the palm of your hand makes a perfect cab. ( It's actually how I get all the flats off the stone).
One of the things I found w/ the plastic composite laps was that it looked great at 600 and 1200 then at 7k all these scratches showed up. It was either subsurface damage finally appearing ( like it does w/ crystalites) or there were some quality control issues with the laps.
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Joined: Tue Jun 12, 2007 6:41 pm Posts: 5534 Location: Massachusetts, USA
FWIW, I have always used felt with CeO. The open structure of the felt holds loads of CeO and it can forgive a multitude of scratches. It will actually remove material. I use a hard felt.
Joined: Tue Jun 12, 2007 6:41 pm Posts: 5534 Location: Massachusetts, USA
Quote:
Do you use a pretty wet felt? I have never really played around too much with cerium on felt and what little I have done has not been successful.
You MUST keep it wet or the stone will fry.
What happens is the felt quickly wears a groove to fit the stone's contours. It takes a lot of polish up. The felt wheel is then reserved for opal and other quatz cabs. Been doing it this way since the '70's.
I use the industrial felt polishing wheels on my faceter, but have used them on cab units as well.
Joined: Tue Oct 17, 2006 11:33 am Posts: 403 Location: New Zealand
Hi
on my travels trough Australia i had all the Time a little Proxon Tool with me that i run of the car batteries .
Cut heaps of opal that way and all the time polished with cerium on felt heads ; its all about finding the right speed -pressure relatio to keep the heat low and get a good polish .
As well if you have to much cerium it will go dry even if the felt behind is wet if you go to fast.
It just gets better and easier more you practice like everything
Joined: Sun Dec 30, 2007 12:01 am Posts: 556 Location: Vancouver, Canada
Just thought I'd put in a vote for Pellon. I have had superior results with much less thrown polish than with felt. It does degrade rapidly but it's cheap.
Joined: Thu Jan 24, 2008 4:01 pm Posts: 1902 Location: Pine City, NY and Dothan, AL
TheGemDr wrote:
Just thought I'd put in a vote for Pellon. I have had superior results with much less thrown polish than with felt. It does degrade rapidly but it's cheap.
Tony.
I've used a layer of Pellon (the thick kind - there are dozens of varieties) on a layer of 1/8" foam. Both from the Wal-Mart fabric and craft department.
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