orange peel or gas bubbles

[Shivan]

G'day all, been having a go at the heart of darkness cut on a piece of synthetic ruby.
http://www.gemologyproject.com/wiki/images/e/e7/Heart_of_Darkness.pdf


Finished the pavilion and was not happy with a few facets so re polished. Two sides are fine but the other two either have tiny gas bubbles or is suffering from an orange peel finish.
I am using a 10X loupe to look at the facets, but am having trouble working out which is my problem. Cant get a good photo as its a small stone at 6mm.


Is there a way to distinguish tiny gas bubbles from an orange peel finish?

[Aussie Sapphire]

Others will hopefully be able to help with more specific advice but just thought I would add this:

Would changing the direction of the lap when polishing help at all?  Sometimes this can be a useful trick to try when polishing is not working for you.

Orange peel can be a tricky one to solve - lots of discussion about it here and on other forums. 

This article may have some useful ideas for you as well:
http://www.thegemdoctor.com/wp/2010/01/is-that-a-scratch/


cheers
Leah

[Shivan]

Thanks for the advise, i have not tried changing directions yet may give it a go and see if it helps.

I had just thought it was a bad polish job till i had a good look with the 10X loupe, then i remembered reading some synthetics had small gas bubbles and wondered if that's what i was looking at. May have to dig the microscope out and see if i can work it out.

[FlashGP]

Hi Shirvan

Andrew posred a great list of causes of "scratches".  I'm  going to forward the link to some facetors in our club.

Although bubbles are a give away for man made rough, I thought they would be microscopic.

Firstly,  what type of loupe are you using.  Loupes aint Loupes.  A number 10 head loupe  is only about a 3x.  10x the area is just a bit over 3x magnification in length.  I had a cheap 10x with 0.5mm graticule from Jaycar.  In reality it was about 3x.

Until I got my good 10x Belomo loupe I thought the 30x loupe was pretty strong.  The 10x magnifies a bit more and is clearer.

The 10x graticules Aussie Sapphire had are pretty  close to a 10x and useful if you intend to enter a faceting comp.  If you can only afford one loupe, this is worth looking at. 

A word of caution, it is easy to mark the graticule, one of these days I'll need a new graticule as I have already chipped mine by bumping it into a piece of quarts while using it.

A cheap digital microscope should set you back under $100.  10x is 10x on them and although a bit of hard to use they can give a reasonable idea of what is happening.  The depth of field is a bit low so it allows you to selectively look into the stone by changing the focus.

Try bouncing the light off the facet from different angles.  This may help you dyetermine if it is bubbles or orange peel.

Regards

[Shivan]

Cheers Flash, my loupe is a belomo from my geological studies and you are right there is a big difference between the cheaper ones.
I have heard of the graticule loupes but have not seen one to know the difference.

Under my head magnifier it just looked like a few facets were a little frosty when bouncing the light. Under the loupe i could see what appeared to be small holes rather than scrathes. This is what i thought was orange peel.
After polishing again and having another close look i thought it reminded me of bubbles. They are tiny though so it is hard to make out. I do have an old micro scope so i will dig it out and see if i can get a better look.

I did have hopes of maybe entering this stone in my clubs comp at the end of the year, otherwise i probably would have just kept going as its on the pavilion.

[FlashGP]

You could enter it anyway.  The flaws fall into ine categiry. You may only lose a mark or two and still get valuable feed back.

[Shivan]

After having a closer look i cant see any bubbles in the stone, so have come to the conclusion it is orange peel.

Will do a bit more reading and try to figure out how to proceed.

[Moth]

For what it is worth my solution to orange peel, as applies to CZ, after pre-polish I polish with 50,000 then 100,00 and find, when orange peel becomes obvious on a facet, if I go back to 50,000 (sometimes even to pre-polish at 15,000) then return to 100,000 I can overcome the problem.  The main problem though is the time it involves - anticipating at least one facet will have OP I have to leave the meets slightly apart to allow for that possibility, which means that I then have to use the polish process to also cut to the meet-points which takes a lot of time - it's OK for a competition stone but not feasible in normal circumstances

[Shivan]

Thanks for that Moth.
This time round i think it may have been a poor prepolish on my part that caused the OP. I was that focused on the meet points because the facets were so small, i forgot to check that they were getting finished properly.

I only have access to 3k and 60k at the moment, so after having no improvement polishing for the second time on 60k i dropped back down to 3k.
I have managed to get rid of the OP, but now have lost a few meet points and am chasing my tail trying to cut everything back to the proper meets.

[FlashGP]

I recently found that polishing from the crown back to the girdle helps minimise the amount of recutting, as the amount the meet moves reduces as you get closer to the girdle. 

But I expect I am preaching to the converted.

[gregchauvier]

Can you explain that a bit more Flash?

[FlashGP]

Consider the facets as in cross section.  They are triangles.  The lower the angle, the higher the ratio between the hyoptenuse and the height.  Hence at low angles small depth changes produce large changes in facet length.  The reverse is true for large angles.

I recently modified the Bar Round One so the bars were cut at 22 and 26 instead of 24.  With only a few degrees between the angles of the split bars, the join swung wildly as I cut the meet points.  When I had the side meet points in, l started on the center line meets.  Large movements in these meets produced no discernable change to the edge meets.

I have also noticed this effect when there is only one or two indexes between girdle facets as on a cushion.

So l have started getting all meets in using 8000 diamond then polishing from the crown down so l can get the meets in on the way down.

if l polish from the girdle up, l often have to go back to the 8000 to bring the shallow facets back to close before polishing them.

Cutting the pavillion of the Weiland Star I cut and polished the first 4 rows as usual as row 4 is step cut.  I then prepolished rows 5 and6 and polished the deepest overcut facet on row 6 then polished row 5 so that meet was established and row 4 a uniform width, then polished the rest of row 6 into place.

When I cut the table, l'll prepolish all meets in place leaving a 5%of H girdle then polish the crown and work down from there.  It shouldmaximise my girdle for setting and minimise the amount of polishing I do.  After all on this 10mm stone 5% of H is about 0.3mm.

Regards
Gordon

[gregchauvier]

Thanks, explained well!

[Orange Pirate]

Excellent tips there Flash with a great explanation. I'll have to give that a go. 


Cheers
OP

[Shivan]

Very interesting. Will take a bit of processing to get my head wrapped around it, but should come in very handy.