Why is 35.5/40.6 not considered super ideal?

[flyingpig]

GOG ASC and WF ACA have the requirement for crown angle between 34 - 35. Some experts have even narrower ranges such as 34.3 - 34.8.
I have seen a few 35.5/40.6 that are just gorgeous in person and online. Some dont have any light leakge. Brighness is just fine confirmed with the IS. Contrast is deep and well defined. Fire is excellent (after all, it sits between TIC and FIC). Many have depth less than 62 percent. Since it is top heavy, you get more stone above the girdle and the stone appears more substantial and offer more volume above the prongs and bezel. For me, it is just perfect, in my theory.

But how come many experts and super ideal cut vendors dont see 35.5/40.6 as a super ideal combo.?

 

[gm89uk]

Great q flyingpig. I always wondered the same thing:
33 degree crown angle too shallow?

There is a discussion here regarding this.

I think one of the main things is accidentally crossing 40.5 to 40.4 pavilion is a bigger deal than a range of 40.7/40.8.

I've also read from trade members that towards 80% LGF are more favourable and from other trade members that towards 75% are more favourable in this combination. I've read from trade members that smaller tables work with higher crowns, but there seems to be more combinations with 35.5/36 crowns that can possibly acquire AGS 0 with tables of 56/57 than 54/55.

http://www.prosumerdiamonds.com/crown-angle/ this article seems to imply that shallower LGF are preferable in steeper crowns. I'd love to hear trade members opinions on what it takes to make a beautiful 35.5/40.6.

 

[John P]

But how come many experts and super ideal cut vendors dont see 35.5/40.6 as a super ideal combo.?

It's just a threshold: 35.0/46.0 stays robust through tables 55-56-57T, with buffers of 54T and 58T on either side of the common super tables.

The 35.5/40.6 enjoys best results paired with a bit smaller table. 56-57T paired with those angles can still make AGS 0, but it's borderline. 58T brings only about 2%.- reduction of performance integrity but that can be enough to move a stone to AGS 1.

http://www.prosumerdiamonds.com/crown-angle/ this article seems to imply that shallower LGF are preferable in steeper crowns. I'd love to hear trade members opinions on what it takes to make a beautiful 35.5/40.6.

I didn't read the article (and wife is waiting to go to dinner) but I'd plan this angular combo with 54T and short lower halves. Give me enough brightness to taste, with some big broadfire.

 

[flyingpig]

The 35.5/40.6 enjoys best results paired with a bit smaller table. 56-57T paired with those angles can still make AGS 0, but it's borderline. 58T brings only about 2%.- reduction of performance integrity but that can be enough to move a stone to AGS 1.

May I interpret this that a carefully crafted 35.5/40.6 with a complementary table and other numbers can be as beautiful as a super ideal 34.5/40.8? If so, may I assume that many super ideal cut vendors don't include any stone with 35.5CA regardless its performance for the sake of brand consistency and just to be safe as 35.5CA only works with certain PA and TB%?

Or will it still suffer a bit of minor deduction, despite the best effort, in brightness/dispersion/leakage/contrast that cannot be revealed or measure by AGS software and ASET? Because I have seen 35.5/40.6 with perfect ASET and NO reduction in any category, but it was still marketed as a 2nd tier brand.

 

[Karl_K]

In my opinion a fairly tight 35.5/40.6 with a matching table and reasonable lowers when well cut with high levels of optical symmetry is a great combo and I have recommended them in the past.
The are every bit as good as other combos in the super-ideal range and give a bit more 3d effect.
The biggest problem is that there are a lot of ANDs in that sentence making it harder to tell others to look for them.
Other combos have a bit more leeway in the specifics.

 

[Karl_K]

As to what a vendor puts in their different categories, they have to draw the line somewhere and they just concentrate on other combos for their main brand.
If that saves me a couple bucks that is an even bigger win.

 

[Karl_K]

There is another factor also, the rules of thumb were put together when the average cutting and process control was much lower than it is today.
Precision cutting was a lot more rare than it is today.
Today there are far more cutting houses capable of doing what was once considered doable only by the specialty precision cutting houses.
There are still some who stand out but the average is not as far behind as before.
With precision cutting and process control you can play the edges more and get some awesome diamonds.

 

[flyingpig]

Thanks for the detailed explanation.
It appears a combination of history, cutting technique, perception, cutting tolerance, branding, etc..

The effects of different TB, PA, lower half % can be easily seen in maginified photos and ASET images. I really like the 3D effect of top heavy diamonds. I was wondering if I was missing anything that conventional assessment tools (ASET/IS/AGS software) don't reveal. My brain says stick with 34.3~34.8, but my heart wants 35.5 or even 36...

 

[Karl_K]

yea that is pretty much it.
The same thing thing applies to 41 degree pavilions and even 80% lgf with the right combination and cutting.
Many years ago there was a cutting house long out of business who was cutting some very superb ~55t/34/41/80% super tight with superb optical symmetry.
A few PS posting dealers were carrying them while others had a fit about them.
I saw them in person locally and they were superb.
My wifes diamond is a recut by them to slightly different numbers but with the same superb cutting.
I still have a soft spot for that combo when well cut.

 

[gm89uk]

I didn't read the article (and wife is waiting to go to dinner) but I'd plan this angular combo with 54T and short lower halves. Give me enough brightness to taste, with some big broadfire.

Thanks John, hope you and your wife enjoyed your dinner.

Karl if I remember right you prefer 80% LGF with 35.5/40.6, is this personal preference or is there a performance reason thats specific with this combination (?over obstruction with shorter LGF)?

 

[Karl_K]

Thanks John, hope you and your wife enjoyed your dinner.

Karl if I remember right you prefer 80% LGF with 35.5/40.6, is this personal preference or is there a performance reason thats specific with this combination (?over obstruction with shorter LGF)?

I feel they have a better balance with 77%+ lgf with GIA rounding that is often 80% but can be 75%.
There will be increased green areas in ASET under the table at 75% actual.
That said it is a relatively minor consideration if they are tight and all the mains stay above 40.5.

 

[Karl_K]

I revisited it in DC and in some cases 75% actual could possibly move it to ags1. It depends on the particulars.
77%+ is a safer target.

 

[Garry H (Cut Nut)]

I did a study on this about 15 years ago.
The info here https://ideal-scope.com/fine-tuning/ refers to Lower Girdle length (GIA mistakenly used depth whcih was silly, and my labelling is wrong too). LGD is a couple % longer than the equivalent LGL. So remove a couple of % for the common now language.
I think, also, that fatter stars have become more popular than they were when I did this work. Remember that there were more diamonds with larger tables back then. My aim was to fatten them up in +60% table stones.

 

[gm89uk]

Hi Garry,

How do you properly convert LGD to LGL? Even if I remove a couple % it still seems a little long? So roughly for a 55% table you'd recommend ~ 81% LGF? Whats is compromised if it's a little shorter.

With regards to table size and the 35.5/40.6 combo:

The 35.5/40.6 enjoys best results paired with a bit smaller table. 56-57T paired with those angles can still make AGS 0, but it's borderline. 58T brings only about 2%.- reduction of performance integrity but that can be enough to move a stone to AGS 1.

With stones like the below (35.5/40.6/5 would the slight deduction in performance not be visible in the ASET?

 

[drk14]

How do you properly convert LGD to LGL?

If my calculations are correct, then the following approximate relationship should hold between LGL (%) and LGD (%), for a given pavilion angle PA (in degrees):

LGD = LGL +(100% - LGL) x [0.0013 x (75 - PA)]

LGL = [LGD - 0.13 x (75 - PA)]/(0.9025 + 0.0013 x PA)

For example, for 83% LGD and 40.6 PA, you would have 82.2% LGL.

 

[John P]

With stones like the below (35.5/40.6/5 would the slight deduction in performance not be visible in the ASET?

Not necessarily. An ASET image is a 2D map showing areas of brightness, contrast and leakage. The AGS grade involves ray-tracing of the diamond’s 3D model at both 30blue & 40blue, and through a practical range of tilt, to gather repeatable totals for BC&L, along with calculated dispersion-potential.

 

[Gustavoboy106]

Hi RockyTalky, I also want to get a 35.5 crown angle even with experts recommendation of 34-35. I truly love fire above all else, did you got it like that? I would like your feedback.

I have an option one is 35.5/40.8
Table 56.5%, Pav: 62.5%

what do think?

 

[flyingpig]

35.5/40.8 can be near superideal or a trainwreck, or somewhere in between. In many cases, there will be light leakage and in some cases wonky pavilion facets.
The 0.2 degree difference in PA makes a huge difference.
Do you have any photo?

 

[Gustavoboy106]

Thanks for reply! I leave you the link below

https://www.brilliantearth.com/lab-diamonds-search/view_detail/8956787/

I have others in mind, but I am waiting for certificate and aset for some of them.

https://www.brilliantearth.com/lab-diamonds-search/view_detail/9277590/

https://www.brilliantearth.com/lab-diamonds-search/view_detail/9277475/

https://www.brilliantearth.com/lab-diamonds-search/view_detail/9277574/

https://www.brilliantearth.com/lab-diamonds-search/view_detail/9294093/

This one is probably to big for my gf she is size 5:
https://www.brilliantearth.com/lab-diamonds-search/view_detail/9090647/


I already bought a natural diamond for 18k but I want to sell it and buy any of of those man made diamonds, use difference for our honeymoon

This is the one I own already, but is J color and I didn't like that really:

My current ring:

Dropbox

www.dropbox.com

My current diamond certificate:

Dropbox

www.dropbox.com

What are your thoughts? I prioritize Fire

Thank you for your time friend

 

[OoohShiny]

Thanks for reply! I leave you the link below

https://www.brilliantearth.com/lab-diamonds-search/view_detail/8956787/

I have others in mind, but I am waiting for certificate and aset for some of them.

https://www.brilliantearth.com/lab-diamonds-search/view_detail/9277590/

https://www.brilliantearth.com/lab-diamonds-search/view_detail/9277475/

https://www.brilliantearth.com/lab-diamonds-search/view_detail/9277574/

https://www.brilliantearth.com/lab-diamonds-search/view_detail/9294093/

This one is probably to big for my gf she is size 5:
https://www.brilliantearth.com/lab-diamonds-search/view_detail/9090647/


I already bought a natural diamond for 18k but I want to sell it and buy any of of those man made diamonds, use difference for our honeymoon

This is the one I own already, but is J color and I didn't like that really:

My current ring:

Dropbox

www.dropbox.com

My current diamond certificate:

Dropbox

www.dropbox.com

What are your thoughts? I prioritize Fire

Thank you for your time friend

If we're talking MMDs, you will have to Report your post and ask for your posts and flyingpig's reply to be moved to the Lab Grown part of the forum!

 

[Garry H (Cut Nut)]

Hi RockyTalky, I also want to get a 35.5 crown angle even with experts recommendation of 34-35. I truly love fire above all else, did you got it like that? I would like your feedback.

I have an option one is 35.5/40.8
Table 56.5%, Pav: 62.5%

what do think?

Supa dupa ideal is a figment of this forums imagination.
I like them too
So does HCA

 

[Gustavoboy106]

MMD or natural, the angles affect the same way, I need only help with angles is not a mmd or natural discussion is an angle discusión

 

[flyingpig]

MMD or natural, the angles affect the same way, I need only help with angles is not a mmd or natural discussion is an angle discusión

I think it is an above-average 35.5/40.8, definitely not a trainwreck. But is it good enough? Hard to tell. The camera and the diamond are not aligned properly.

 

[Gustavoboy106]

Flyinpig thanks for reply!
I requested aset image, hope that it is good and post it here when I do

 

[AV_]

I'd plan this angular combo with 54T and short lower halves. Give me enough brightness to taste, with some big broadfire.

What is your reasoning?

... I may have something similar in mind from another therad, but cannot play with ray tracing where I am, just 'back of the envelope' ...

 

[Garry H (Cut Nut)]

40.8 is not 40.6 which is the old thread you reopened?
there canbe very big differences. The +1 degree crown angle is less critical than the pavilion angle nd GIA and labs rounds all this data