Deviation in crown angles Why?

[pyramid]

On a Sarin report

Crown Angle 34.6 (34.3 - 34.9)

Pavillion Angle 40.8 (40.6 - 40.9)

Table size 54.1%


Why is the tightness on the crown angles a deviation of between 34.9 and 34.3 , does this mean the diamond could have a tilted table?

 

[Garry H (Cut Nut)]

could be, but it could be totally wonky

too little info P

 

[pyramid]

http://www.whiteflash.com/hearts_arrows/A-Cut-Above-H-A-cut-diamond-66400.htm#


more information?

 

[Garry H (Cut Nut)]

It would appear that the table is tilted by about 0.1 - 0.2 degrees and there is about 0.2-0.4 degrees of crown angle deviation from an imaginary avergae axis through the middle of the 3D diampnd.

 

[Garry H (Cut Nut)]

probably dust on the stage of the scanner

 

[kcoursolle]

Date: 4/5/2007 10:49:54 PM
Author:Pyramid
On a Sarin report

Crown Angle 34.6 (34.3 - 34.9)

Pavillion Angle 40.8 (40.6 - 40.9)

Table size 54.1%


Why is the tightness on the crown angles a deviation of between 34.9 and 34.3 , does this mean the diamond could have a tilted table?

confidence intervals, like in statistics?

 

[pyramid]

Thanks Garry H and KCoursolle. Garry H So would this diamond be considered tight enough? What is your opinion Strmrdr or anyone else who reads this?

 

[Paul-Antwerp]

Date: 4/5/2007 10:49:54 PM
Author:Pyramid
On a Sarin report

Crown Angle 34.6 (34.3 - 34.9)

Pavillion Angle 40.8 (40.6 - 40.9)

Table size 54.1%


Why is the tightness on the crown angles a deviation of between 34.9 and 34.3 , does this mean the diamond could have a tilted table?

Crown angles are more difficult to control than pavilion angles, hence generally more deviation. There is absolutely no reason to connect this to a tilted table, or whatever other cause, nor to dust on the scanner.

As for Garry''s comments above, I cannot understand where he bases this on, and if his percentages are somewhat correct, my question would be: so what? Or like the former French president used to say: Et alors?

Live long,

 

[pyramid]

Thanks Paul. So would you consider this tight enough then?

 

[Garry H (Cut Nut)]

Date: 4/6/2007 7:03:56 AM
Author: Paul-Antwerp

Date: 4/5/2007 10:49:54 PM
Author:Pyramid
On a Sarin report

Crown Angle 34.6 (34.3 - 34.9)

Pavillion Angle 40.8 (40.6 - 40.9)

Table size 54.1%


Why is the tightness on the crown angles a deviation of between 34.9 and 34.3 , does this mean the diamond could have a tilted table?

Crown angles are more difficult to control than pavilion angles, hence generally more deviation. There is absolutely no reason to connect this to a tilted table, or whatever other cause, nor to dust on the scanner.

As for Garry''s comments above, I cannot understand where he bases this on, and if his percentages are somewhat correct, my question would be: so what? Or like the former French president used to say: Et alors?

Live long,

Hi Paul, you need to translate for me?

But if this stone had those distortions without the table being tilted it would not have the Hearts pattern shown on the WF website - they would look like this:

 

[pyramid]

So Garry would that make this a bad choice for an ACA ideal cut diamond, in your opinion?

 

[Garry H (Cut Nut)]

as I wrote above Pyramid, the diamond probably was resting on some dust on the scanner - so it is not the diamond that has the problem.

However if the table is slightly tilted it makes no difference to its optical properties as far as any humans eyesight can ever see. But it makes a difference to the measured parameters because the people who devised the systems were not very smart.

Read all about it here
http://www.gemology.ru/cut/english/symmetry/6.htm

It is a nice diamond

 

[strmrdr]

Date: 4/6/2007 6:14:27 AM
Author: Pyramid
Thanks Garry H and KCoursolle. Garry H So would this diamond be considered tight enough? What is your opinion Strmrdr or anyone else who reads this?

Tight enough to be beautiful sure ....
Tight enough to make my ocd happy.... no...
The range is not that unusual even in ideal cuts.
Paul and a 2 or 3 other cutters cut tighter but the optical symmetry is there so there is small practical difference unless your a workmanship nut like me :}
But keep in mind trying to play the tightness game with sarin scans is like trying to catch the wind in a net, the scanner just isn''t up too it.

 

[mosher]

Date: 4/5/2007 10:49:54 PM
Author:Pyramid
On a Sarin report

Crown Angle 34.6 (34.3 - 34.9)

Pavillion Angle 40.8 (40.6 - 40.9)

Table size 54.1%


Why is the tightness on the crown angles a deviation of between 34.9 and 34.3 , does this mean the diamond could have a tilted table?

The difference in the crown angle will be due to the girdle if it were the table it would be out of centre along with the culet. the table can only be tilted if the variance is on one half of the stone in which case the culet would be of certre. In both cases the certificate should have a lower grade of symmetry.

 

[pyramid]

Date: 4/6/2007 8:15:53 PM
Author: mosher

Date: 4/5/2007 10:49:54 PM
Author:Pyramid
On a Sarin report

Crown Angle 34.6 (34.3 - 34.9)

Pavillion Angle 40.8 (40.6 - 40.9)

Table size 54.1%


Why is the tightness on the crown angles a deviation of between 34.9 and 34.3 , does this mean the diamond could have a tilted table?

The difference in the crown angle will be due to the girdle if it were the table it would be out of centre along with the culet. the table can only be tilted if the variance is on one half of the stone in which case the culet would be of certre. In both cases the certificate should have a lower grade of symmetry.

mosher

When you say ''In both cases'' do you mean the table being off symmetry (1) and the culet being off (2), or did you mean the girdle should have lowered the symmetry grade?

 

[mosher]

If the girdle is thin to thick this would not impact the symmetry but could account for the difference in the crown angle, that would be a cut grade issue.

The table or the culet out of centre would be a symmetry issue.

I suspect it is the girdle were the angle is being altered.

 

[pyramid]

Thank you everyone (GarryH, KCoursolle, Paul-Antwerp, Storm, Mosher) for your replies to this thread.

 

[Garry H (Cut Nut)]

Date: 4/6/2007 8:15:53 PM
Author: mosher

Date: 4/5/2007 10:49:54 PM
Author:Pyramid
On a Sarin report

Crown Angle 34.6 (34.3 - 34.9)

Pavillion Angle 40.8 (40.6 - 40.9)

Table size 54.1%


Why is the tightness on the crown angles a deviation of between 34.9 and 34.3 , does this mean the diamond could have a tilted table?

The difference in the crown angle will be due to the girdle if it were the table it would be out of centre along with the culet. the table can only be tilted if the variance is on one half of the stone in which case the culet would be of certre. In both cases the certificate should have a lower grade of symmetry.

Mosher if the girdle was to vary and be thicker on one side than the other then this need not effect the crown angle but would definietly effect the pavilion angle.

The girdle on the Sarin is thin to thin, and varies from 0.8% to 1.2% - which is not a lot, but would cause more than 0.3 degrees pavilion variance.

Unfortunatly the Sarin scan does not give crown heifght differences.

 

[He Scores]

Simply stated you have a stone that has optical symetry without physical symetry. Cutting for patterning is all about what the stone looks like. The bottom is more important than the top and the top is made to make everything copesetic, if there is such a word.

Paul''s right. The bottom is easier to get tight with regard to the bottom main angles because the stone is resting on the table. Not so in most top pots. If the stone had a tipped table it could easily be seen on the manufacturers report as the tipping variation would be equal but opposite on the top and bottom.

Few people understand the "fudging" that goes on in diamond cutting. It all starts with the roundness and straightness of the girdle. If it''s slightly out of round (I''ve never seen a report that wasn''t), then right away, other things like angle, depth in girdle and straightness of facets has to be fudged in some way or the other.

These are the things my patented cut analysis sytem judges. Things done by the cutter that observation can see.

Bill Bray
BrayScore.com

"because looks can be decieving"