January 24 Through February 4—TUCSON, ARIZONA: Annual show
Welcome to the GemologyOnline.com Forum
A non-profit Forum for the exchange of gemological ideas
It is currently Thu Mar 28, 2024 2:36 pm

All times are UTC - 4 hours




Post new topic Reply to topic  [ 16 posts ]  Go to page 1, 2  Next
Author Message
 Post subject: Opal polishing update
PostPosted: Wed Dec 17, 2008 8:51 pm 
Offline
Valued Contributor

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.


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Wed Dec 17, 2008 10:01 pm 
Offline
Gold Member

Joined: Thu Apr 17, 2008 1:47 am
Posts: 1350
Location: Pacific Northwest
Are you wet sanding? If so, try dry and vice versa.

_________________
I just dreamed that I was a butterfly.


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Thu Dec 18, 2008 7:08 am 
Offline
Gold Member
User avatar

Joined: Thu May 29, 2008 8:32 am
Posts: 1730
Location: Suwanee, GA US
Are you sure you are not pulling sand out of a pocket you are contacting? Just a little pit that is hiding?


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Thu Dec 18, 2008 9:09 am 
Offline
Valued Contributor

Joined: Tue Feb 05, 2008 10:18 pm
Posts: 285
Location: Las Vegas
allen wrote:
Are you wet sanding? If so, try dry and vice versa.


May try this but all other stones went just fine with wet sanding.


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Thu Dec 18, 2008 9:10 am 
Offline
Valued Contributor

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.


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Tue Aug 04, 2009 12:44 am 
Offline
Active Member

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.

opal also does not like worn sandpaper.


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Tue Aug 04, 2009 3:46 am 
Offline
Platinum Member
User avatar

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.

_________________
Custom Gemstone Cutting and various other activities!


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Tue Aug 04, 2009 6:39 am 
Offline
Moderator: Lapidary Arts and Tools
User avatar

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.

_________________
https://gearloose.co/


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Tue Aug 04, 2009 8:36 am 
Offline
Gemology Online Veteran
User avatar

Joined: Thu Jul 17, 2008 12:08 pm
Posts: 647
Location: Edina, MN
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.

Obviously I am doing something wrong since so many report good results.

The more info that people can give on this method the better! It would be useful for opals, feldspar and Quartz.

(What about heat build up?)

_________________
Gems are purchased because they are pretty, so they should be as pretty as possible!

https://www.johndyergems.com
Artisitic and designer cut gems

https://www.ultratecfacetingmachine.com
Authorized Ultra Tec dealer.


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Tue Aug 04, 2009 9:11 am 
Offline
Moderator: Lapidary Arts and Tools
User avatar

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.

_________________
https://gearloose.co/


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Tue Aug 04, 2009 9:44 am 
Offline
Valued Contributor

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


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Tue Aug 04, 2009 10:44 am 
Offline
Gemology Online Veteran
User avatar

Joined: Thu Jul 17, 2008 12:08 pm
Posts: 647
Location: Edina, MN
It probably makes a powerful mess all around the work area I suppose.

Do people use the pink or the white cerium?

Where do you get those "industrial" felt pads? They fit on a standard faceting machine?

_________________
Gems are purchased because they are pretty, so they should be as pretty as possible!

https://www.johndyergems.com
Artisitic and designer cut gems

https://www.ultratecfacetingmachine.com
Authorized Ultra Tec dealer.


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Tue Aug 04, 2009 12:43 pm 
Offline
Moderator: Lapidary Arts and Tools
User avatar

Joined: Tue Jun 12, 2007 6:41 pm
Posts: 5534
Location: Massachusetts, USA
Quote:
Where do you get those "industrial" felt pads? They fit on a standard faceting machine?



You will need an extra extended bolt and washer.
The cut and paste cannot be formatted correctly, but here is the general idea:

1/2" Arbor hole.


http://www.mcmaster.com/#4815a14/=31klxk

Medium Hard
Dia. x Density Density

Thick. Each Each

6" x 1/4" 4815A11 $18.40
4815A25 $22.45

6" x 1/2" 4815A12 27.81
4815A26 33.17

6" x 3/4" 4815A13 33.69
4815A27 36.40

6" x 1" 4815A14 40.49
4815A28 43.18

_________________
https://gearloose.co/


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Tue Aug 04, 2009 1:54 pm 
Offline
Gemology Online Veteran
User avatar

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.

Tony.

_________________
www.thegemdoctor.com
Beautiful British Columbia


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Tue Aug 04, 2009 3:03 pm 
Offline
Gold Member
User avatar

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.


Top
 Profile  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 16 posts ]  Go to page 1, 2  Next

All times are UTC - 4 hours


Who is online

Users browsing this forum: No registered users and 25 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group
Gemology Style ported to phpBB3 by Christian Bullock