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Recut - Calculating the loss

Wink

Ideal_Rock
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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.
It’s my pleasure @Lessics. You are one of the most knowledgeable and helpful contributors here so the least you should expect is some reciprocation.

Reading this thread I believe @Karl_K posted an important distinction. True old-world OECs were cut entirely outside the philosophies of today’s diamonds. They cannot be compared to high light return OECs. They were cut for entirely different goals. Art is a good word for it, but it goes even deeper than that. You might say it’s like painting in oils back then, where now color laser printers are used. That is not to say a talented cutter cannot revisit the old ways, but the depths of true antiques challenge cost-effectiveness.

Wink
 

prs

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Just want to point, you crown & pavilion mains are misaligned in the three sketches.
:eek-2: :eek-2: :eek-2: Thank you for pointing that out. Just goes to show I still have a lot to learn!!!!
 

prs

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Just want to point, you crown & pavilion mains are misaligned in the three sketches.
That also explains why I've been having so much difficulty with the flower petal pattern! =)
 

Garry H (Cut Nut)

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Just want to point, you crown & pavilion mains are misaligned in the three sketches.
Well picked Yoram.
This is very common in mellee or stars under 0.02ct where when turning the stone over in the pot or holder the cutter misaligns the facets.
I once upon a time put 40 stones all with great Ideal-scope light return into a small box - 20 normal and 20 with a half facet twist ad showed them to all my staff asking which were best.
Those that just looked face on preferred the regular. Those that rocked the stones preferred the half twist.
So I now include them on the basis that very small diamonds are rarely facing directly at you.

I should have made a video like this one for single cuts and full cuts:
 

Garry H (Cut Nut)

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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?
It not about %'s - its always about angles. The two animals are dogs and cats
 

AV_

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@prs www beats pen & paper

[with few & not too relevant exceptions]
 

prs

Brilliant_Rock
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Thank you @AV_ but I am committed to doing this the Old European Way. :mrgreen2:
 
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AV_

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Then, Peruzzi's book comes to mind [unless there is better.] I agree that back of the envelope ray tracing is better for reading ready-made diamonds, than DiamCalc is & ... this is all we do ... I got to it after, for no good reason.
 
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Garry H (Cut Nut)

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Then, Peruzzi's book comes to mind [unless there is better.] I agree that back of the envelope ray tracing is better for reading ready-made diamonds, than DiamCalc is & ... this is all we do ... I got to it after, for no good reason.
Sorry AV, what do you mean back ov envelop vs DiamCalc?
Take Lessics ID image or an old cut for example - using DiamCalc I can quite easily model that stone. It will have a very shallow pavilion and very steep crown angle with a small table - a combination that works well in modern diamonds too - but pushes the boundaries past where PSérs like - especially because of the very small spread.
That stone would get a reasonable HCA score but bad spread would drag it down.
 

Karl_K

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Sorry AV, what do you mean back ov envelop vs DiamCalc?
Take Lessics ID image or an old cut for example - using DiamCalc I can quite easily model that stone. It will have a very shallow pavilion and very steep crown angle with a small table - a combination that works well in modern diamonds too - but pushes the boundaries past where PSérs like - especially because of the very small spread.
That stone would get a reasonable HCA score but bad spread would drag it down.
If you don't care about spread you can make some amazing and interesting designs that would never see the light in a list driven world.
 

Garry H (Cut Nut)

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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
Lessics here is your recut - which can only be achieved by shrinking the diameter and loosing 1/4 of the weight and almost halving the value:
1588130437072.png
 

Garry H (Cut Nut)

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It’s my pleasure @Lessics. You are one of the most knowledgeable and helpful contributors here so the least you should expect is some reciprocation.

Reading this thread I believe @Karl_K posted an important distinction. True old-world OECs were cut entirely outside the philosophies of today’s diamonds. They cannot be compared to high light return OECs. They were cut for entirely different goals. Art is a good word for it, but it goes even deeper than that. You might say it’s like painting in oils back then, where now color laser printers are used. That is not to say a talented cutter cannot revisit the old ways, but the depths of true antiques challenge cost-effectiveness.

Wink
Hi Wink,
I don't think that is right. Jonathon for example and some other vendors we know have made a business out of making new-old cuts. I have often considered it but m busy enough anyway. I certainly have cutters who can make old cuts with way better weight retention than modern rounds from 'makeable' rough and certain other shapes.
And that means that great performance is possible with cookie cutter repeatability (although there is even more room to swindle a bit her or there).
 

LightBright

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Hi Wink,
I don't think that is right. Jonathon for example and some other vendors we know have made a business out of making new-old cuts. I have often considered it but m busy enough anyway. I certainly have cutters who can make old cuts with way better weight retention than modern rounds from 'makeable' rough and certain other shapes.
And that means that great performance is possible with cookie cutter repeatability (although there is even more room to swindle a bit her or there).
Thank you for all of your posts here, they have been very informative. I wish we had more antique cut style diamonds to choose from. I’d choose a beautiful and artistic “newly cut’ antique style diamond over an MRB. Diamonds are mostly a once in a lifetime purchase done by people who have never seen an antique style cut. When one actually sees broad facets and high crowns/small tables (lending a 3D chunkiness) the appeal is dramatic and obvious! Add to that the romance of historical artistry. That is why some of us covet these styles.
 

Wink

Ideal_Rock
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Hi Wink,
I don't think that is right. Jonathon for example and some other vendors we know have made a business out of making new-old cuts. I have often considered it but m busy enough anyway. I certainly have cutters who can make old cuts with way better weight retention than modern rounds from 'makeable' rough and certain other shapes.
And that means that great performance is possible with cookie cutter repeatability (although there is even more room to swindle a bit her or there).
I think you misunderstood my post my friend. I’m not talking about performance, which may shock you. I’m referencing history and the completely different philosophies of old world cutters. Diamonds were sold in stores using gas lamps. There were no electric lights, so the cutters worked to bring out reflections and refractions from the lanterns under which they were working. They were also table-grinding. One rough = one diamond. Absolutely different from now. Painting in oils, so to speak.

Rotary sawing and electric store lighting changed everything. So where you say “great performance is possible” today I know that very well. But it’s not what I was referencing.

Wink
 

AV_

Ideal_Rock
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AV, what do you mean back ov envelop vs DiamCalc?
I was thinking that even grossly simplified models - simple enough for 'back of the envelope' intuition, tell enough to point to what makes the difference between two diamonds: eg. just the main crown pavilion angles, thought for reflectance & dispersion, never mind minor facets commaning contrast patterns... I would probably never try to reconstruct a single screenshot of DiamCalc on a drawing borad - dam' chore!, but this is beyond the point while holding a beautiful diamond & wondering 'what is it that I like'?
 
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Garry H (Cut Nut)

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Gotcha Wink.
Seems strange to me though that AV and others on this thread seem to think old cuts should be accepted for what they are.
I remember the hue and cry when Laurence Graff bought a famous historical blue and did some small repolishing including closing the culet a little.
I mean what is it with culet's? Why do old cut folk love open holes with 83% leakage.

Yoram and Karl - I agree. Spread limits beauty. But I am depressed that we do not already have wonderful creative new cuts in synthetic rough where yield and rarity are not issues!!!!

Maybe I should retire and start a new business making beauty out of alternative materials???
 

AV_

Ideal_Rock
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@Garry H (Cut Nut) Do not mistake this choice of mine for tolerance - it is the larger facets that make old brilliants beautiful to me more or less irrespective of proportions or shape; then, the culet is a cue for the overall point symmetry of the design. I am still mourning that flat, blue star brilliant cut.
 

prs

Brilliant_Rock
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Gotcha Wink.
Seems strange to me though that AV and others on this thread seem to think old cuts should be accepted for what they are.
I remember the hue and cry when Laurence Graff bought a famous historical blue and did some small repolishing including closing the culet a little.
I mean what is it with culet's? Why do old cut folk love open holes with 83% leakage.

Yoram and Karl - I agree. Spread limits beauty. But I am depressed that we do not already have wonderful creative new cuts in synthetic rough where yield and rarity are not issues!!!!

Maybe I should retire and start a new business making beauty out of alternative materials???
Garry, I believe there might be three reasons for wanting the culet:

1. You can't have the Kozibe effect without a culet.

2. A culet might actually help light return for diamonds with high pavilion angles. Many OECs were cut with deep pavilions to preserve weight.

3. For marketing reasons you want a GIA cert stating your diamond is an "Old European". Just any old culet won't do it, you need it to be slightly large (5%) or larger! :)
 
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Garry H (Cut Nut)

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Garry, I believe there might be three reasons for wanting the culet:
1. You can't have the Kozibe effect without a culet. you would want that???? more leakage ?? See below
2. A culet might actually help light return for diamonds with high pavilion angles. Many OECs were cut with deep pavilions to preserve weight. ? Modelled that in DiamCalc - all you get is nail head effects in rare ray directions
3. For marketing reasons you want a GIA cert stating your diamond is an "Old European". Just any old culet won't do it, you need it to be slightly large (5%) or larger! :) and if you sunbit an old stone with no culet they will not call it OEC?
 

diagem

Ideal_Rock
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Gotcha Wink.
Seems strange to me though that AV and others on this thread seem to think old cuts should be accepted for what they are.
I remember the hue and cry when Laurence Graff bought a famous historical blue and did some small repolishing including closing the culet a little.
I mean what is it with culet's? Why do old cut folk love open holes with 83% leakage.

Yoram and Karl - I agree. Spread limits beauty. But I am depressed that we do not already have wonderful creative new cuts in synthetic rough where yield and rarity are not issues!!!!

Maybe I should retire and start a new business making beauty out of alternative materials???
Hi Garry..., you sound a bit confused..., all ok down under? :devil:
Where on earth did you ever read my writing saying that "spread limits beauty"?? You should know me by now already, we all have our individual beauty, remember?

As per your first comment about old cuts, it seems that light performance is your primary meaning for beauty. I say light performance is only partial to the big word "beauty"..., cant argue with the fact that old cuts are not assessed in the same manner as modern cuts.

Based on the popularity in recent years for old cuts, I am guessing leakage is also part of the beauty pie!! As I have learned and passed my experiences on, Kozibe optical effects have as much weight in the appeal of a diamond, you see leakage, I see light play and craftsmanship.

What Graff did with the Wittelsbach Blue was quite controversial merely because he re-touched a significant historical diamond, maybe one of the most significant diamonds ever. The Wittelsbach can be dated back to the mid 17th century and might have been the first recorded brilliant style diamond because of its importance.

The Wittelsbach recut was not to minimize the wonderful huge culet it still possesses, Graff's main objective was to rid of the greyish undertones were noticeable in the face-up view. For such objectives Graff is no less than a maven but altering and putting such a significant diamond back on the cutting wheel is what is rightfully controversial.
 

Karl_K

Ideal_Rock
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Based on the popularity in recent years for old cuts, I am guessing leakage is also part of the beauty pie!! As I have learned and passed my experiences on, Kozibe optical effects have as much weight in the appeal of a diamond, you see leakage, I see light play and craftsmanship.
I see patterns.
Something that modern light performance grading totally ignores.
 

prs

Brilliant_Rock
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1. You can't have the Kozibe effect without a culet. you would want that???? more leakage ?? See below
Yoram has explained this perfectly.


2. A culet might actually help light return for diamonds with high pavilion angles. Many OECs were cut with deep pavilions to preserve weight. ? Modelled that in DiamCalc - all you get is nail head effects in rare ray directions
Excerpt taken from Al Gilbertson's book "The American Cut"

The American Cut Pg 182.png


3. For marketing reasons you want a GIA cert stating your diamond is an "Old European". Just any old culet won't do it, you need it to be slightly large (5%) or larger! :) and if you sunbit an old stone with no culet they will not call it OEC?
GIA cut crieria for round diamonds:

GIA Cut Criteria.png
 

Garry H (Cut Nut)

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Hi Garry..., you sound a bit confused..., all ok down under? :devil:
Where on earth did you ever read my writing saying that "spread limits beauty"?? You should know me by now already, we all have our individual beauty, remember?

As per your first comment about old cuts, it seems that light performance is your primary meaning for beauty. I say light performance is only partial to the big word "beauty"..., cant argue with the fact that old cuts are not assessed in the same manner as modern cuts.

Based on the popularity in recent years for old cuts, I am guessing leakage is also part of the beauty pie!! As I have learned and passed my experiences on, Kozibe optical effects have as much weight in the appeal of a diamond, you see leakage, I see light play and craftsmanship.

What Graff did with the Wittelsbach Blue was quite controversial merely because he re-touched a significant historical diamond, maybe one of the most significant diamonds ever. The Wittelsbach can be dated back to the mid 17th century and might have been the first recorded brilliant style diamond because of its importance.

The Wittelsbach recut was not to minimize the wonderful huge culet it still possesses, Graff's main objective was to rid of the greyish undertones were noticeable in the face-up view. For such objectives Graff is no less than a maven but altering and putting such a significant diamond back on the cutting wheel is what is rightfully controversial.
You mis-interpreted my missive Yoram - spread desires limit what people will buy - but that limits to options to cut beautiful functioning diamonds.
If for example a piece of rough dictates it is viable to be turned into an octavia and the small spread means it costs more - that is sad because hacking more weight of the diamond and turning it into a generic bit of glassy rubbish is sad.
We are not disagreeing my friend :)
 

AV_

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@Lessics I had forgotten one flat brilliant worth seeing - www ; the second picture shows a main windowing with tilt, betraying low depth, I'd guess barely 50% [the table looks about 55% & could be read better in the first shot, modernistic rest, I think - long stars, not too short lgf, etc.]

The color in the photo is too much.

@John Pollard @Serg
 
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Lessics

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@Lessics I had forgotten one flat brilliant worth seeing - www ; the second picture shows a main windowing with tilt, betraying low depth, I'd guess barely 50% [the table looks about 55% & could be read better in the first shot, modernistic rest, I think - long stars, not too short lgf, etc.]

The color in the photo is too much.

@John Pollard @Serg
Very Interesting thank you for sharing!
 
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prs

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@prs dear Peter, you and your wife saw this diamond in person? Or did I misunderstand that? If so could you maybe elaborate on the cut and performance of the diamond in your opinion. I see it only has a 59,x % depth. Which would be considered quite shallow for an oec. Thank you for your time!


Yes, we saw the diamond in person. We were actually visiting David Klass and we mentioned we might have an interest in an OEC. He said he'd heard from one of his diamond dealer friends that Grace had an absolutely fabulous OEC, and would we like to see it. It was the first OEC we had ever seen in person, and it was extraordinarily beautiful. It's the diamond that convinced my wife she wanted to upgrade to an OEC.

The caveat has to be we knew nothing about OECs at that time, but to the untrained eye, it was indeed gorgeous. Looking at the photos now, the facet pattern looks really good. It also seemed to face up whiter than an L, so must have good light return. Yes, the depth is shallow, but so is @dreamer_dachsie's fabulous OEC. How these shallow OECs have such great light return, and look so good is a mystery I'm still trying to unravel. :)
 

oldminer

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Diamonds, especially ones that were cut 20 years or more ago, tend to have been cut to retain a good balance between appearance and weight retention. Few were cut to maximize light return and old cuts were often re-cut to make them a bit more visually modern, remove chips, and to retain as much weight as practical. Cutters can make estimates of such work readily since they often are asked to do exactly such normal re-cutting.

The kind of re-cutting which is unusual, such as cutting a reasonably made modern stone into a semi-old cut is not the norm and not something cutters generally want to do. The big problem is that you hand over a diamond and get back one which won't look like what you started with. How will you identify it is "your original diamond"? You might not like the outcome and you can't just reverse the process. It puts way to much risk of unhappiness into the situation, I'm afraid. You will be told there will be too much weight loss and might be warned that how the diamond will look may not be exactly what you had in mind. These are good warnings from experience and should be carefully listened to.

The suggestion to find a diamond you like and to sell or trade the one you have may be the most sensible way to go forward. It will cost more money possibly than what a re-cut would coast, but there is zero risk of becoming unhappy and owning a lower weight diamond that you don't really like. If the diamond does not bring you pleasure, then there is no way I'd suggest taking a risk on the whole complex process. Changing stones is a much safer and happier way to go.

No doubt, some folks have taken the risk and been very happy with their choice to proceed. A lot depends on their expectations and how precise or reasonable their goals were to begin with. Some people are easy to please with reasonable expectations, while many, or most, are understandably more difficult to please. You need to understand your inner self to take the chances.
 

Lessics

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@prs You write that looking back it looks really good in the picture. After all your research would you still be comfortable buying such a shallow oec? :)

@oldminer thank you very much for your thought out response. It definitely gives me food for thought. It would cost me at least double to buy a new oec diamond. Also the color/ clarity combo in this Diamond can’t be beaten. But I will definitely think long and hard about any decision.
 
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