Question 1: AGS triple 0

[tlikinim]

I''m having trouble understanding how an elite AGS triple 0 "ideally cut" diamond (based on ideal proportions, cut, and symmetery) can produce poor light performance. I read the article on Light Scope and how H&A diamonds don''t guarantee good light performance. My understanding is that ideal proportions will give you greatest light performance. Please help me to understand.

 

[JohnQuixote]

Date: 1/24/2006 11:38:42 AM
Author:tlikinim
I'm having trouble understanding how an elite AGS triple 0 'ideally cut' diamond (based on ideal proportions, cut, and symmetery) can produce poor light performance. I read the article on Light Scope and how H&A diamonds don't guarantee good light performance. My understanding is that ideal proportions will give you greatest light performance. Please help me to understand.

Traditional Ideal proportions were used by the AGS from 1995-2005 to award the 'Ideal' grade. They were a good start - and may still be used to separate above-average diamonds from average and poorly cut diamonds.

Diamonds at the outer limits of the traditional range may not perform as well in all lighting environments as those cut to the heart of traditional ideal proportions. For instance, steep/deep pavilion and crown angle combinations on the one end (for example, >41.0 PA avg combined with steep crown angles)...or shallow/shallow combos on the other end (for example,
The AGS introduced a new grading system last July. This one is based on direct light performance, not just proportions configurations. Some of those outer limit combos will no longer make the 'ideal' grade now that direct light performance is judged. Conversely, some configurations (esp with larger tables) that used to be excluded from 'ideal' now make it in. The new AGS system is more robust.

 

[belle]

first you need to understand that the effect of 'hearts and arrows' is due to facet arrangement and the presence of them does not have anything to do with proportions. proportions are the angles at which each of the facets are cut and have nothing to do with how they are lined up (creating h&a effect). you can have two diamonds with the same great proportions and different facet patterning. light leakage won't come from the presence or absense of h&a patterning, it comes from certain combinations in the proportions.

 

[oldminer]

For many years, all we had to go on was ranges of cut parameters that cutters felt met the best standards of cutting, the "Ideal Cut". Several researcher type cutters, including Tolkowsky, determined different but quite similar sets of parameters that would work very well along with expert cutting.

However, cutters are a sly and wily group, always looking to get the best out of their rough diamonds, which often includes getting a little more weight at the expense of beauty. They did their homework and found they could cut Ideal cuts that were not truly ideal. A lot of AGS 0 and AGS 000 stones from the older system suffered a little to a moderate amount from this smart game that was being played. Diamonds cut to my old AGA 1A Cut Class did not suffer from this, but I was very strict in my charts. People often pointed them out specifically as being right but sort of beyond commercially viable due to the tightness of the parameters.

That game is not over, but there is always a new game beginning. It will be exciting to see how cutters work the angles and parameters within the newer, smarter systems that are now being employed. If there are little loopholes, we will be sure to have them pointed out to us by those who always seek to work around the edges. Nothing is totally new.