Another question about girdle thickness.......

[Carlotta]

Last night a poster had a question about a girdle thickness/variation.....
I did a search here and found so many threads that I didn''t research all of them......also looked at the tutorial....

Anyway, here is another question:

When I looked at the sarins for several stones being considered, The girdles were listed as (for example) .7-1.3, thin to medium. But on the AGS cert, the girdle was like .68-3.5. The numbers were similar for several stones.

Why are the numbers so different on the sarins and certs???

Also, one of the threads I pulled up last night (posted by Pricesope) stated that the different LABS all report girdle measurements differently!!!

Quite confusing!!!

 

[oldminer]

1. Sarin devices do not measure girdles all that accurately. We live with it.
2. Labs do choose to use differing portions of the girdle for descritpions of thickness. We live with this, too.

Other than a girdle being very thin a more prone to chipping or very thick and just wasting carat weight without giving you visual diameter, the girdle thickness is not truly of great importance. From slightly thin to thick, it is all about the same for most purposes. You can use girdle thickness in screening stones, but it is not a prime ingedient in end decision making within quite q wide range.

 

[Garry H (Cut Nut)]

Date: 5/20/2006 2:22:40 PM
Author:Carlotta
Last night a poster had a question about a girdle thickness/variation.....
I did a search here and found so many threads that I didn''t research all of them......also looked at the tutorial....

Anyway, here is another question:

When I looked at the sarins for several stones being considered, The girdles were listed as (for example) .7-1.3, thin to medium. But on the AGS cert, the girdle was like .68-3.5. The numbers were similar for several stones.

Why are the numbers so different on the sarins and certs???

Also, one of the threads I pulled up last night (posted by Pricesope) stated that the different LABS all report girdle measurements differently!!!

Quite confusing!!!

I think that AGS now measure at the tickest part - the mains and minor facet junction - which is usually 1.7 or 1.8% thicker than the valley part, and they measure the very thinnest part - which is usually the thinnest valley.
So 1.8 plus 1.3 = 3.1% - which is quite possible given the thickest main might not be normally related to the tickest valley part.

Does that help?

 

[Capitol Bill]

Date: 5/20/2006 5:54:20 PM
Author: oldminer
1. Sarin devices do not measure girdles all that accurately. We live with it.

2. Labs do choose to use differing portions of the girdle for descritpions of thickness. We live with this, too.


Other than a girdle being very thin a more prone to chipping or very thick and just wasting carat weight without giving you visual diameter, the girdle thickness is not truly of great importance. From slightly thin to thick, it is all about the same for most purposes. You can use girdle thickness in screening stones, but it is not a prime ingedient in end decision making within quite q wide range.

I would only add that one should always place more credibility on the labs' numbers because they use the high-end sarin model. Most dealers use the base model that isn't quite as accurate. Granted, all of these machines only perform as accurately as they are calibrated.

Bill Scherlag

 

[Modified Brilliant]

Date: 5/20/2006 8:55:24 PM
Author: Capitol Bill

Date: 5/20/2006 5:54:20 PM
Author: oldminer
1. Sarin devices do not measure girdles all that accurately. We live with it.

2. Labs do choose to use differing portions of the girdle for descritpions of thickness. We live with this, too.


Other than a girdle being very thin a more prone to chipping or very thick and just wasting carat weight without giving you visual diameter, the girdle thickness is not truly of great importance. From slightly thin to thick, it is all about the same for most purposes. You can use girdle thickness in screening stones, but it is not a prime ingedient in end decision making within quite q wide range.

I would only add that one should always place more credibility on the labs'' numbers because they use the high-end sarin model. Most dealers use the base model that isn''t quite as accurate. Granted, all of these machines only perform as accurately as they are calibrated.

Bill Scherlag

The same calibration issues regarding diameter measurements exist and vary slightly from lab to lab. However, there seems to be more calibration issues regarding the Sarin. I agree with Dave and Bill.

www.metrojewelryappraisers.com

 

[oldminer]

Just to make it clear I have no complaint with Sarin and their highly durable devices. I have owned the high end unit several years and it is bullet-proof. Calibration is quite stable, but the ability to be accurate is not perfect regardless of calibration. There is reasonably slight machine error which is not changed by any calibration techniques.

When one uses a Sarin to generate physical measures a little error means nothing. If one takes these slightly erroneous measures to the next step to do ray tracing, 3-D modelling and light performance estimates, then we do get into a problem of accuracy and repeatability. For measures alone, the better units are good enough and faster than other methods. For prediction of performance, I know there will be problems.