Recut - Calculating the loss

[xxxxxx]

Hi everybody,
is there a way of estimating the loss of weight/diameter of a diamond after a recut without a specialized software.

For example if I had a MRB


Carat: 4.12
Depth: 61.2%
Table: 56.5%
Crown Angle: 34.7*
Pavillion Angle: 40.9


Measurements: 10.34 x 10.39 x 6.34

and would want it to be cut into an floral OEC with a slightly large Culet.

with at least
Depth: 63%
Table: ideally 55% or under
Crown Angle 36.9 - 37.1°
Pavilion Angle 40.7 - 40.9°


How much smaller would the diameter be?

Is there a way I can estimate this without being a pro?

Thank you for your

 

[Karl_K]

One does not fit into the other in any economically viable way.
The size and ct weight loss would be crazy high.

 

[xxxxxx]

One does not fit into the other in any economically viable way.
The size and ct weight loss would be crazy high.

Thank you for answering and bringing the analogy of the diamonds fitting into each other. That analogy gives me a new way of thinking of it.

 

[WinkHPD]

So, by my quick and dirty estimation, your current diamond is approximately 4.15 cts. I am not going to spend the time to even estimate what it might weigh after being cut down, but I agree with Karl that it would lose lot of weight.

You might be better off selling this diamond and buying a diamond with your desired characteristics. You would have to research to see if such a diamond is available and then see how much you can get for your current diamond.

Wink

 

[xxxxxx]

What an honor that all the experts are weighing in on my topic! Thank you @Wink

But also a shame that there would be such a big loss.

 

[AV_]

You ccould show the stone to a cutter and ask them to propose the features of a recut with minimal weight loss - lets say, to improve brilliance and give a transitional flavour. I would not want to guess details any further, this is not such a simple job. I would expect to be given a small set of potential results, all good to the point that I can let the dice choose (that is to say, give green light to the recut!)

2p

 

[xxxxxx]

You ccould show the stone to a cutter and ask them to propose the features of a recut with minimal weight loss - lets say, to improve brilliance and give a transitional flavour. I would not want to guess details any further, this is not such a simple job. I would expect to be given a small set of potential results, all good to the point that I can let the dice choose (that is to say, give green light to the recut!)

2p

I actually did show it to Ashley from Southwest Cutters He Said he could get an OEC Flavour by only taking away 0.15mm. But he wasn’t very elaborate and as this project will take a bit I didn‘t want to annoy him with further questions.
But when I’m closer to pulling the trigger I’ll keep your suggestion mind. Thank you!

 

[Serg]

I actually did show it to Ashley from Southwest Cutters He Said he could get an OEC Flavour by only taking away 0.15mm. But he wasn’t very elaborate and as this project will take a bit I didn‘t want to annoy him with further questions.
But when I’m closer to pulling the trigger I’ll keep your suggestion mind. Thank you!

RE:He Said he could get an OEC Flavour by only taking away 0.15mm.

Crown angle is just 36,5 if table Table will above 56.5%.
it is necessary to reduce girdle diameter more significantly to receive crown angle 37 and Table 55.
In such case the diamond after recut will less than 4ct

 

[headlight]

I’ve had 3 diamonds recut... we don’t dictate the proportions, the characteristics dictate what’s possible, regardless of weight loss.
This would be a total leap of faith for you because you won’t know exactly what it will look like. With my recuts, they were RB being made into better RBs. You have a substantial diamond and there’s value there. If you don’t love it and would love this completely other flavor, sell your stone and get what you love!

 

[foxinsox]

I actually did show it to Ashley from Southwest Cutters He Said he could get an OEC Flavour by only taking away 0.15mm. But he wasn’t very elaborate and as this project will take a bit I didn‘t want to annoy him with further questions.
But when I’m closer to pulling the trigger I’ll keep your suggestion mind. Thank you!

Not any sort of expert but I would wonder if the OEC ‘flavour’ and comparatively small weight loss means they’d only be doing something to the pavilion to make fat petals rather than thin arrows?

 

[kenny]

I don't care about weight loss.
I care about light-performance improvement.

 

[Garry H (Cut Nut)]

Why not start with a way deeper lessor really poor cut?

 

[Karl_K]

Not any sort of expert but I would wonder if the OEC ‘flavour’ and comparatively small weight loss means they’d only be doing something to the pavilion to make fat petals rather than thin arrows?

yea that little loss would have to involve making something like some people refere to as a transitional cut.
A full oec transformation to the range mentioned would be a much bigger loss.

 

[Malha777]

Hi, if the stone you have right now doesn’t have any major issues (chips/cracks) I’d consider selling it and buying a stone with the desired characteristics with the profit. The weight loss would be very substantial and also not completely predictable because, as someone already mentioned, the new cut would be dictated by the characteristics of the diamond itself.

 

[diagem]

Hi everybody,
is there a way of estimating the loss of weight/diameter of a diamond after a recut without a specialized software.

For example if I had a MRB


Carat: 4.12
Depth: 61.2%
Table: 56.5%
Crown Angle: 34.7*
Pavillion Angle: 40.9


Measurements: 10.34 x 10.39 x 6.34

and would want it to be cut into an floral OEC with a slightly large Culet.

with at least
Depth: 63%
Table: ideally 55% or under
Crown Angle 36.9 - 37.1°
Pavilion Angle 40.7 - 40.9°


How much smaller would the diameter be?

Is there a way I can estimate this without being a pro?

Thank you for your

All good answers but would like to get a bit deeper as its not such an easy makeover as it sounds.
Firstly, to try to estimate results would require two very important measurements that were not mentioned, the crown height percentage and the girdle thickness!

MRB's usually are cut to significantly lower crown heights vs. OEC's ( <15.5% vs. >17.5%), this fact by itself usualy forces for a diameter reduction. If you add the steeping of the crown angles from 34.7 to 37.0 degrees will translate to even more diameter reduction. Higher crown heights will also allow for the <53% table semi-requirement.

So based on such a scenario, the thinner the girdle the grater the diameter reduction.
finding older round brilliants (e.g. 1970-1990) with extremely thick girdles will always help as long as you have a decent crown height of at least 15%.

Unfortunately most MRB's today are planned and cut to the lower side of the allowed crown height proportions (12-13%).

 

[xxxxxx]

I‘m so lucky to have all of you weigh in. Thank you @diagem for going further into detail. Especially about the crown height proportions!

@Garry H (Cut Nut) so if I had a 64% depth diamond it would be far easier (effective) to achieve a 63% depth?

Does anybody know how a 61-62% Old European Cut Diamond differs in looks and performance to a 63-64% OEC Diamond?

For example the AVR and CER Lines of repro antique diamonds both have slightly different flavors (avrs deeper and more round bubbly facets - cers more flowery transitional type less deep diamonds) - but both claim to have ideal light performance wir to be ideally cut. Could a 61% OEC diamond still have ideal light Performance?

 

[AV_]

Does anybody know how a 61-62% Old European Cut Diamond differs in looks and performance to a 63-64% OEC Diamond?

The flat old stones are what I had in mind above, I find that the broad facets make them look nothin like moderns, kin to the deep OEC most talked about around here despite their brilliance being in a different taste. I am not sure if there are any around here, but there was one large cushion with such proportions at Gem Concepts not long ago.

 

[prs]

Increasing the crown angle, in combination with reducing the table size, is the killer on your caWhy do you want to increase the crown a

Hi everybody,
is there a way of estimating the loss of weight/diameter of a diamond after a recut without a specialized software.

For example if I had a MRB


Carat: 4.12
Depth: 61.2%
Table: 56.5%
Crown Angle: 34.7*
Pavillion Angle: 40.9


Measurements: 10.34 x 10.39 x 6.34

and would want it to be cut into an floral OEC with a slightly large Culet.

with at least
Depth: 63%
Table: ideally 55% or under
Crown Angle 36.9 - 37.1°
Pavilion Angle 40.7 - 40.9°


How much smaller would the diameter be?

Is there a way I can estimate this without being a pro?

Thank you for your

Well nobody has answered your question as to how to estimate the loss, so I guess you would need some kind of 3D software to figure it out. The main reason for significant weight loss in your example is the increase in crown angle. Combine that with the smaller table and you'd be looking at a major reduction in diameter.

My question is why do you want to increase the CA? How about just shaving the table down to 53% with a CA of about 32.5° You would retain the diameter, there would be minimal weight loss, and that combination of angles still gives a decent light return. I suspect that 's what Southwest had in mind.

 

[yssie]

The couple of shallow, fat-pavilioned, small-tabled RBs (they’re definitely quite rare) that I’ve seen in-person had issues with over-obstruction and prominent fisheye at small tilt angle.

 

[xxxxxx]

@AV_ Thank you for pointing out Gem Concepts Cushions they are truly beautiful. The 26 Carat has this slight brown rim around the center (is this what we call Fish eye) when it gets tilted - where as the 15 Carat doesn’t Display this phenomena as pronounced. I would like to avoid that - is it due to the shallow depth and the large table? https://gemconcepts.net/product/two-superb-antique-old-mine-cut-diamonds/ (There are videos linked on that site of these special and impressive diamonds)


@prs thats true what you’re saying. I just love the look of the CERs so I was going after their proportions approx. but obviously it doesn’t seem effective in my situation. Now I just have to think if I’m okay with a shallower larger tabled cut.

@yssie thank you for sharing! Even though it’s not what I want to accept (:

So there’s not really a good combination of specs to have a good looking shallower (~62%) and big table (~55%) chunky flowery round diamond

 

[Karl_K]

Could a 61% OEC diamond still have ideal light Performance?

This is going to take a while and hopefully others will weigh in and im going to tick some people off.
When it comes to oec's and fancies forget the word "ideal" and "ideal light performance" as it applied to super-ideal mrb diamonds.
They are used to box mrbs in to a certain ranges of looks and reaction to lighting and that just don't apply to fancy cuts.

They are much more varied.
A high light return oec type stone can be made with a huge range of proportions and with a huge range of appearances.
Even high light return is problematic because you have to balance patterns, contrast, brightness, scintillation and fire.
There are no free lunches to change one you change another.
For example you want a brighter oec you trade off some of the moody contrast and fire in some lighting(you made it show brightness in that lighting instead of fire).
You have to think of fancy cuts as art with many variations of "ideal" many different styles and many different looks.
As oec cuts marketed as ideal while similar in concept that they are oec and cut with matched angles and facet placement when you look at the details they are as many differences as similarities.
That is the art.

 

[prs]

The couple of shallow, fat-pavilioned, small-tabled RBs (they’re definitely quite rare) that I’ve seen in-person had issues with over-obstruction and prominent fisheye at small tilt angle.

AGS would seem to indicate it's easier to get good light return with shallower crowns rather than steeper. Of course if by fat pavilion you mean a too deep PA, then yes, that can cause problems with any round diamond. Here's the AGS chart for a 53% table.

 

[prs]

@prs thats true what you’re saying. I just love the look of the CERs so I was going after their proportions approx. but obviously it doesn’t seem effective in my situation. Now I just have to think if I’m okay with a shallower larger tabled cut.

@yssie thank you for sharing! Even though it’s not what I want to accept (:

So there’s not really a good combination of specs to have a good looking shallower (~62%) and big table (~55%) chunky flowery round diamond

What's a CER?

From what I've learned, and I know this is pretty obvious, but it took me a little while to figure it out, as table size decreases the crown facets surrounding the table automatically increase in size. So if you want chunky facets the table has to be below a certain size. GIA picked 53% as the magic number.

 

[AV_]

I cannot say off the cuff what are threshold numbers for having the girdle's reflection onto the pavilion seen at some angle TBD, but I do remember a couple of beautiful, shallow, old round brilliants! [will followup]

 

[Slickk]

What's a CER?

Canera European Round. Victor Canera’s gorgeous OEC.

 

[AV_]

ctd

WWW

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I did not realize that reports are no longer available ... ,( I remember the ring stone was shallow by modern standards, with a not so high crown, but small table; the rest - don't ask!

 

[xxxxxx]

@Karl_K Thank your taking the time to write out your thoughts. So it really is art. I wish there were more diamond artists (obviously the Octavia is a great example). Maybe if it the price of lab growns go down there will be more experiments. I hope you get well soon!

@prs thank you for sharing the table, where can one find these tables?
Interesting but what exactly makes the facets chunky at a table below 53%?


@AV_ Now I’ll finally remember that it’s the reflection of the girdle that I’m not too fond of. Thank you for reminding me! Those diamonds you posted are still so very beautiful.

 

[prs]

[USER=97043]@prs thank you for sharing the table, where can one find these tables?
Interesting but what exactly makes the facets chunky at a table below 53%?

The table is extracted from a pdf file I downloaded two years ago from a link posted in a PriceScope thread. Unfortunately I don't remember what thread.

It's really up to individual taste as to what makes for chunky crown facets. You may remember I had a recent thread discussing this very topic. Here's a diagram I have showing how the size of the crown facets vary with table sizes of 45%, 50%, and 53%. The diagram shows all the facets surrounding the table in black. You can see that as the table gets bigger these facets get smaller. You can imagine how chunky they would look with a 40% table!

The diagram also includes the pavilion main facets, shown in blue. It does not include the lower half facets that produce the petal shape underneath the table, I'm still working on those.

 

[xxxxxx]

The table is extracted from a pdf file I downloaded two years ago from a link posted in a PriceScope thread. Unfortunately I don't remember what thread.

It's really up to individual taste as to what makes for chunky crown facets. You may remember I had a recent thread discussing this very topic. Here's a diagram I have showing how the size of the crown facets vary with table sizes of 45%, 50%, and 53%. The diagram shows all the facets surrounding the table in black. You can see that as the table gets bigger these facets get smaller. You can imagine how chunky they would look with a 40% table!

The diagram also includes the pavilion main facets, shown in blue. It does not include the lower half facets that produce the petal shape underneath the table, I'm still working on those.

Thanks for reminding me and reposting this image. Definitely helps me imagining it a bit better.

 

[diagem]

The table is extracted from a pdf file I downloaded two years ago from a link posted in a PriceScope thread. Unfortunately I don't remember what thread.

It's really up to individual taste as to what makes for chunky crown facets. You may remember I had a recent thread discussing this very topic. Here's a diagram I have showing how the size of the crown facets vary with table sizes of 45%, 50%, and 53%. The diagram shows all the facets surrounding the table in black. You can see that as the table gets bigger these facets get smaller. You can imagine how chunky they would look with a 40% table!

The diagram also includes the pavilion main facets, shown in blue. It does not include the lower half facets that produce the petal shape underneath the table, I'm still working on those.

Just want to point, you crown & pavilion mains are misaligned in the three sketches.