Cut Advisor

[lge995e2]

I have some questions about the cut advisor. If you score a 1 (all excellent) on the TIC scale - how do you translate this into the BIC scale.

I purchased a BIC stone not a TIC stone, so how do I use the TIC standard. Does it even need to be translated? Are a BIC and a TIC actually the same stone - we are just using different scales to describe their cut dimensions?

I hope someone can TRANSLATE this email into english and let me know what to take away from the Cut Advisor. Maybe "The HCA and Ideal-Scope Cut Quality Crusader!" can rescue me from my ignorance.

Thanks!

 

[optimized]

You know, that's an interesting question that I hadn't thought of before. So, the question is (if I'm reading it correctly): Could a 1.0 FIC stone hypothetically score a 2.5 on the BIC range? Could a TIC score of 0.9 have a poor FIC score? I'd be interested in knowing how the different scores interrelate. I wouldn't presume to ask for the (understandably secret) proprietary formulas, but I would be interested in knowing how the three classes interact with each other.

I guess one measure of this is the individual light return/fire/scintillation ratings, which I assume roughly correlates to the different scales. But, my mind then jumps to another question: Does an "excellent" rating for fire on a TIC carry the same weight as an "excellent" fire rating on an FIC, or does the fact that the scale is already geared to a fiery cut on the FIC mean that there is even MORE fire in an "excellent" FIC versus the TIC? Does any of this make sense???

" thread).

Garry, YOU'RE UP, MATE! Give us some of that good oil, oh purveyor of ridgy-didge cut wisdom! (I rifled an online Aussie slang dictionary for that line. Can you tell? )

-Tim
[/u]

 

[Garry H (Cut Nut)]

http://www.diamond-cut.com.au/23_bicfic.htm
TIC is the central area on the little chart.

The only way you can make a stone change from BIC to TIC is recut it.

Its bed time

 

[optimized]

Garry,

I appreciate the link to your site, but I was wondering if you could shed a bit more light on the questions lge995e2 and I asked earlier in this thread, which I'll summarize below.

[*]
Could a high-scoring BIC diamond actually have a low score on one of the other scales? (My guess is that it could since the criteria is different for each scale).

Is there any way to tell what the score for a TIC would be on the BIC/FIC scales? I realize the number wouldn't be terribly useful, but it would be interesting to see how the scales correlate to each other. I still like the idea of a drop-down box on the Cut Adviser page that would allow the user to select the scale used, or perhaps the ability to just have the Cut Adviser give three values, one for each scale.

Are the Light Return/Fire/Scintillation ratings weighted the same for each class? As an example, does an "excellent" score for fire on an FIC stone indicate a similar level of fire as an "excellent" for fire on a BIC or TIC stone, or are the scores related to something like "fire relative to other stones within the same class"?


Thanks Garry. Any info would be appreciated.

-Tim

 

[Garry H (Cut Nut)]

Tim there is only one scale.
To be an ideal cut the stone must have <2.0 score.
Then it is possible for the stone to have a shallow crown angle = BIC, medium crown angle = TIC and steep crown angle = FIC.

I thought the explanation at http://www.diamond-cut.com.au/23_bicfic.htm was quite simple. Obviuosly it is not.

BIC Brilliant Ideal Cut Crown angle is less than 32.5°
TIC Tolkowsky Ideal Cut Crown angles between 32.5° and 35.5°
FIC Firey Ideal Cut Crown angle is more than 35.5°

So for instance a diamond with a deeper pavilion and shallower crown can be ideal cut because it returns more light than a tolkowsky stone. But has less fire. It is a BIC.
etc etc.

FIC's must have shallow pavilions or otherwise they leak too much light and can not be ideal cut.

Is that clear Tim?

 

[optimized]

"Tim there is only one scale."

Thanks Garry, that does help clear it up for me. I guess I've been reading the statement "0.9 - Excellent - within TIC range" from the Cut Adviser page as meaning there were different "scales" that the diamonds were being plotted on rather than the "range" statement that's actually displayed. Rereading it (keeping in mind your comment that there is only one scale) makes me wonder how I got confused in the first place as the statement on the Cut Adviser page seems obvious to me now. Doh! Guess I had a brain-freeze. Thanks for the clarification...

-Tim

 

[Mara]

Interesting..so a diamond can only be TIC, BIC or FIC..no overlap. Thanks for the clarification Garry!

So someone who was *specifically* looking for a FIC would look for a shallower pavilion, a BIC a shallower crown, and TIC a balance of both?

So could one assume that a stone with a shallower pav and a deeper crown would be a FIC? and a shallower crown AND deeper pavilion equal BIC? Or is there no direct relation between the crown and pavilion? Hmm I am confusing myself now.

 

[Mara]

Playing around with the HCA a bit...here are examples of BIC, TIC and FIC pretty close to 0. Interesting to see how the numbers correlate when you move them around.

BIC:
D: 57
T: 59
CA: 31
PA: 40.7
Score: .3 BIC (all excellents)

TIC:
D: 60
T: 57
CA: 34
PA: 40.5
Score: .2 TIC (all excellents)

FIC:
D: 61
T: 54
CA: 36
PA: 40
Score: .3 FIC (all excellents)

 

[dymonite]

Cut nut,

Are those crown angles absolute values or vary according to table size???

My TIC diamond, HCA 1.1 is excellent for light return AND fire - I thougt you had to trade off between the two with a TIC stone.

FYI

6.03-5.98 x 3.52
Depth 58.6
Table 61.5
CA 32.7
PA 40.9
Cu - none

 

[Garry H (Cut Nut)]

Your stone is close to the border of TIC BIC.

The selection of angles was somewhat arbitrary.
It is possible that table size should also be considered, as slightly larger table sizes would tend to be a little better light returners, and a little less firey. But where to stop?

 

[dymonite]

Perhaps these rules of thumb are not that helpful

e.g. shallow stone = brilliance, deeper stone = fire, small table = fire, large table = brilliance

You would have to say my stone is on the shallow side with a largish table yet it scores quite well on fire. Are the 'rules' empirical observations, mere speculation or confirmed with optical theory? What gives?