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OEC Ideal Cut?

Karl_K

Ideal_Rock
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This is a prosumer forum with hundreds of threads debating MRB cut down to the nearest 0.1°, and yet no one seems to question why the diamond trade had chosen to keep OEC cut details hidden from the consumer.
Not secrets, its more like hardly anyone cares.
A couple vendors went with a couple different good combos that score well on the AGS system and market them.
Pretty much everyone else does not care.
 

Karl_K

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I wish you a speedy recovery @Karl_K !

I can’t really tell the difference between the pictures you generated. Inder that the stars are smaller from picture to picture but somehow it doesn’t really change the overall look for my eyes.
Face up and static that particular combo is not fussy about the stars, which is what I was showing.
Viewing them in person, moving and in different lighting there would be appearance and personality differences but its not huge.
 

Karl_K

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What is interesting is that the images look similar but using my preferred DiamCalc brightness calculation(that I use as an indicator in my own work) there is a ~10% range in brightness across the different lgf%.
The peak is when the lowers end near the table edge when looking down at the wire diagram from the top.
This seems to the case most of the time.
wireframe.jpg
 
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Lessics

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Not secrets, its more like hardly anyone cares.
A couple vendors went with a couple different good combos that score well on the AGS system and market them.
Pretty much everyone else does not care.
As you have designed the Octavia (such an outstanding diamond) - do you think these two OEC vendors were copying from each other with there new cut old European cuts? Or is it like the MRB which should be allowed. Would It be plagiarism if somebody has a diamond recut to the same specs of a diamond out of their inventory?

I hope your getting well soon!
 

Karl_K

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As you have designed the Octavia (such an outstanding diamond) - do you think these two OEC vendors were copying from each other with there new cut old European cuts? Or is it like the MRB which should be allowed. Would It be plagiarism if somebody has a diamond recut to the same specs of a diamond out of their inventory?

I hope your getting well soon!
wow loaded questions.
First the design is over a 100 years old even older than MRB configuration which has the same general facet structure and has been cut in 10s of thousands of different configurations over the years.

Or another way the mrb is just another variation of an oec under a different name so why would it be different?

No they are not direct copies of each other, they have different parameters. No different than an ACA vs CBI.
No one owns the right to well cut oec diamonds.

Why would someone copy someone else's product when there are so many other combinations that achieve the same goal?
 

Lessics

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Thank you for sharing your view. I’ve always wondered why there was a discussion about who had the Right to sell and ideal „new“ antique cut.
 

muesli

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This thread is super interesting, will follow it for sure.

I will keep my fingers crossed that you and your wife will find the right diamond for you :).
 

prs

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Not secrets, its more like hardly anyone cares.
A couple vendors went with a couple different good combos that score well on the AGS system and market them.
Pretty much everyone else does not care.
It's certainly true that GIA don't care. They know consumers buy diamonds based on their GIA certs, and GIA put huge amounts of effort into maintaining their reputation for honesty, consistency, and integrity. Quite why they agreed to participate in a scheme that keeps vital information hidden from consumers is beyond me. The folks who worked out this deal must have been lower level people because the criteria they set up to designate an Old European Cut are a joke.

I know for sure there are a lot of OEC fans on this board who care!
 

prs

Brilliant_Rock
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This thread is super interesting, will follow it for sure.

I will keep my fingers crossed that you and your wife will find the right diamond for you :).
Thank you @muesli, it may take awhile but we'll get there!

One thing I just noticed going thru all the photos of the beautiful OECs here on PS is that many of them have something in common. The lines that outline the star facets run in a continuous straight line from the lines that outline the table. Here's an example of what I mean, and to even things up I used an August Vintage photo this time.

AVC 2.064ct OEC 1A.jpg

I always wondered why they called those triangular facets "stars". Now I know! :)

It doesn't seem to matter if the table is larger or smaller, if those facet lines are aligned it's likely to be a beautiful OEC. Take a look at your favorite OEC photos and see if this checks out. There are some gorgeous OECs that don't follow this rule, but quite a lot do!

The star length% actually vary quite a lot with table, but the end result always seems to be a beautiful diamond. I need to do more research, but if this pans out you won't need a ruler to measure the facet lengths, just look at the photo. :clap: This diagram shows how the facet lengths vary, I omitted the lowers because I'm still working to fully understand how they work.

OEC Facet Diag2 T45,50,55S30,35,42.jpg
 

Karl_K

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Remember for steep crowns the larger the table the shorter the stars need to be to avoid over steep uppers in relation to the pavilion.
You criteria is the opposite.
 

Lessics

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Thank you @muesli, it may take awhile but we'll get there!

One thing I just noticed going thru all the photos of the beautiful OECs here on PS is that many of them have something in common. The lines that outline the star facets run in a continuous straight line from the lines that outline the table. Here's an example of what I mean, and to even things up I used an August Vintage photo this time.

AVC 2.064ct OEC 1A.jpg

I always wondered why they called those triangular facets "stars". Now I know! :)

It doesn't seem to matter if the table is larger or smaller, if those facet lines are aligned it's likely to be a beautiful OEC. Take a look at your favorite OEC photos and see if this checks out. There are some gorgeous OECs that don't follow this rule, but quite a lot do!

The star length% actually vary quite a lot with table, but the end result always seems to be a beautiful diamond. I need to do more research, but if this pans out you won't need a ruler to measure the facet lengths, just look at the photo. :clap: This diagram shows how the facet lengths vary, I omitted the lowers because I'm still working to fully understand how they work.

OEC Facet Diag2 T45,50,55S30,35,42.jpg
Maybe this read especially the first chapter will be of interest for you!

 

prs

Brilliant_Rock
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Sorry, but its not a workable criteria.
Remember for steep crowns the larger the table the shorter the stars need to be to avoid over steep uppers in relation to the pavilion.
You criteria is the opposite.
No need to be sorry Karl, this wouldn't be the first mistake I've ever made!

I'm here to learn, so please tell me exactly which of these three aligned crown facet combinations you find objectionable.

OEC Facet Diag2 T45,50,55S30,35,42.jpg
 

AV_

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It doesn't seem to matter if the table is larger or smaller, if those facet lines are aligned it's likely to be a beautiful OEC...
There are some gorgeous OECs that don't follow this rule, but quite a lot do!
This makes sense to me: the squares pattern depends on crown/pavilion & mains relationships - much like the much more sung arrows, so they could well be dependent on happy proportions.

I am much more inclined to read such patterns of than anything, and ranges of proportions can be recognized by them, o course [such collections of patterns were made during the development of the HCA, or so I recall @Garry H (Cut Nut) @Serg, if not for OEC proportions]

If I were to have a diamond cut, I'd probably take aside a couple of days to put my wished into numbers although I am quite sure I will end with a suite [be it a sampler of round brillaint variants? historical? immaginary!? a gradation of what property! - just a dozen would do, perhaps], not a single model, not by a long shot.
 
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Karl_K

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No need to be sorry Karl, this wouldn't be the first mistake I've ever made!

I'm here to learn, so please tell me exactly which of these three aligned crown facet combinations you find objectionable.

OEC Facet Diag2 T45,50,55S30,35,42.jpg
Depends on the crown angle and a lesser extent the lower girdles and the pavilion angle.
 

prs

Brilliant_Rock
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Depends on the crown angle and a lesser extent the lower girdles and the pavilion angle.
At what crown angle do any of these combinations become problematic? Could you be more specific please.
 

prs

Brilliant_Rock
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Our search for an OEC began a couple of months ago. DW and I had been discussing an upgrade, and whilst she almost certainly wanted another MRB, she expressed an interest in looking at OECs. Shortly afterwards we happened to be visiting DKJ and asked David where we could go to see a good looking OEC. David said he'd heard that Jewels by Grace had a fantastic OEC, and would we like to see it. So here's a LINK to the first OEC we saw in person, and of course DW fell in love.

Here's a photo of this magnificent 6.19ct beauty. :love::love::love:

6.19ct 1A.jpg

You can see the crown facets are almost perfectly aligned

6.19ct 1B.jpg

We didn't know anything about OEC facet patterns back then, but it's interesting that we were immediately drawn to an aligned pattern. Unfortunately the price was a tad over our budget :eek-2: and the search began. =)2
 

Karl_K

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At what crown angle do any of these combinations become problematic? Could you be more specific please.
To many variables of CA PA LGF% for an easy answer.
The 45% 30% will work with a much steeper crown than 55% 42%.
 

AV_

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@prs I have noticed the ring - perhaps at a different seller; the tsone is quite something. [so is Chemistry - I have had little to do with just some particular subject & it made me happy; 'wish I had known better twenty years ago]

on another hand: I have not had time to think through the overlapping squares patern, what comes to mind is simple: this is a crown pattern, where the table to star & table to kite angles are such, that the projections onto the table plane are 90° angles etc. - this gives star size; the rest is about projections onto the pavilion... The 6.19 seems to do everything very well - it is possibly less bright than the revivals (OEC constructed to fit ASET criteria) but with more play of light (more widely divergent reflections off the crown facets, so the stone shows its sum total brighteness with a little movement rather than in a static face up position).

off the cuff


noting an impression: might ut be at in these old stones the pavilions, not the crown, yields conteast? - this would tally with the once appreciation of culet reflections & such
 

prs

Brilliant_Rock
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To many variables of CA PA LGF% for an easy answer.
The 45% 30% will work with a much steeper crown than 55% 42%.
Karl, let me clear away the variables so you can give me a more specific explanation as to why my aligned crown facet idea doesn't work.

We know the lowers have to be visible thru the table in order to make the petals in the flower pattern common to all the most beautiful OECs. I haven't yet figured out exactly how far the lowers should extend into the table, but for now I'm going with 15%.

We know a PA of 40.8° is the optimum for an MRB, so until I find out why it isn't the optimum for an OEC, that's what I'm going to go with.

Here's the modified drawing that adds the missing variables to my three aligned crown facet examples.

OEC Facet Diag2 T45,50,55S30,35,42L70,65,60.jpg

So Karl, I'm still way down the learning curve, so please give me the crown angles that cause these three combinations to be problematic.

1) T:45%, S:30%, L:70%, PA:40.8°
1) T:50%, S:35%, L:65%, PA:40.8°
1) T:55%, S:42%, L:60%, PA:40.8°

Thanks and best regards, Peter
 
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Karl_K

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We know the lowers have to be visible thru the table in order to make the petals in the flower pattern common to all the most beautiful OECs. I haven't yet figured out exactly how far the lowers should extend into the table, but for now I'm going with 15%.
Source?
With most combos the best place for light return in an oec is lowers ending close the edge of the table as you look at the wire outline from the top.
It also results in nice patterns.
 

prs

Brilliant_Rock
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OEC's are more about the facet pattern than about light return. Both August Vintage and Victor Canera's OEC style diamonds have lowers that extend into the table by amounts approximately similar to my 15%. It would seem they both chose beauty over light return.

I'm still learning and expect to have to change a lot of things as i go up the curve. How about just putting up with my naivety and going with the variables I selected?
 

Karl_K

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OEC's are more about the facet pattern than about light return. Both August Vintage and Victor Canera's OEC style diamonds have lowers that extend into the table by amounts approximately similar to my 15%. It would seem they both chose beauty over light return.

I'm still learning and expect to have to change a lot of things as i go up the curve. How about just putting up with my naivety and going with the variables I selected?
How about I spend my time not taking orders from someone on the internet instead?
 

prs

Brilliant_Rock
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It doesn't seem to matter if the table is larger or smaller, if those facet lines are aligned it's likely to be a beautiful OEC.
Sorry, but its not a workable criteria.
Remember for steep crowns the larger the table the shorter the stars need to be to avoid over steep uppers in relation to the pavilion.
You criteria is the opposite.
How about I spend my time not taking orders from someone on the internet instead?
No offense intended Karl, but it's you who chose to post that my aligned facet idea is not a workable criteria. However when asked to say why it's not workable you seem reluctant or unable to defend your position.

You've mentioned "steep crowns" in many of your posts in this thread. The problem is I don't know what you mean by "steep" and I need to know that specifically so I can better understand your posts.
 

Karl_K

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You've mentioned "steep crowns" in many of your posts in this thread. The problem is I don't know what you mean by "steep" and I need to know that specifically so I can better understand your posts.
Steep is not a certain number, steep is relative.
What is steep depends on the table size, pavilion angle, lgf length, and to a lesser degree lgf angle and ugf angle relationship which can modify it some what.
A strait line of the table and stars is not a good indication of those things being in a good relationship with each other.
 

prs

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Maybe this read especially the first chapter will be of interest for you!


@Lessics thanks for the book reference. I obviously needed to know more about the history of how OECs were cut, and have been making my way thru Al Gilbertson's book. Lots of really interesting stuff. Apparently European cutters were aligning the star facets with the table facet as far back as the second half of the 18th century, and definitely by 1818.


The American Cut Pg 32.png


The American Henry Morse, perhaps the first cutter in the world to cut for beauty rather than weight, also seemed to believe in aligned crown facets. This is a hand sketch made at the time detailing how Morse famously cut the Tiffany II yellow diamond in 1883-84.


The American Cut Pg 51.png


A 3D scan of a mold of this diamond allowed an exact replica to be made.


The American Cut Pg 53 (2).png


The star and table facets are very closely aligned, and I do believe the lower girdle facets extend under the table. :eek-2::eek-2::eek-2:

Maybe I'm looking for an "Old American Cut" rather than an "old European Cut". =)2
 

AV_

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Figure 2.9 speaks to me [what else is new] - I do not quite know, but wish to work out if/how not symmetrical cuts may have rules yet.

thinking out loud


(digressing - 1820s cuts - www, the collection is consistent enough for me to assume that the stones were at least adjusted to the standard of the day; the center is very round)
 
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prs

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I've spent the last few weeks reading up on old cuts, and going thru all the old OEC threads here on PriceScope. I am more than ever convinced that aligned table and star facets are not only workable, they are exceedingly beautiful. Henry Morse had them when he famously cut the Tiffany II yellow diamond. Marcel Tolkowsky's facet diagrams in his revolutionary 1919 publication show aligned crown facets. The crown facets on August Vintage OECs are aligned, and many of the beautiful OECs shown here on PS have aligned facets.

It's certainly all down to personal preference, but the perfect squares of aligned crown facets is the pattern I will be looking for.

OEC Fig 2B T45,50,53 S30,35,40.jpg

Here's the same diagram adding the other crown facets.

OEC Fig 2A T45,50,53 S30,35,40.jpg

I found the flower petal pattern under the table to be a little more challenging until @diagem kindly pointed out my pavilion facets were misaligned. :eek-2: I think I've got it figured out now, although I couldn't believe my results at first. I don't think GIA were aware of the flower petal pattern when they set a maximum of 60% on the lower girdle facets. I have been totally unable to create that pattern with LGFs that short.
 

prs

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In order to figure out the flower petal pattern under the table, I started off again using the average OEC table of 50%, and with varying lower half facet lengths to see how they looked.

OEC Fig 10A T50,50,50 S35,35,35 L55,60,65.jpg

GIA have an OEC cut criteria that lower half lengths should be less than or equal to 60%, so I was amazed that a length of 55% did not produce petals, and they just began to show at 60%. The pattern began to look pretty good at 65%, so I experimented with even longer lengths.

OEC Fig 10B T50,50,50 S35,35,35 L70,68,65.jpg

70% didn't look quite right to me, although 68% looked good. DW preferred the 65% so that's what counts of course. I went thru the same exercise with other table sizes and this is how I ended up.

OEC Fig 13 T45,50,53 S30,35,40 L70,65,63.jpg

Once the flower petals are in place it becomes easier to see the effect table size has on the look of the overall pattern. They all look really beautiful, but I think I like the 45% and 50% table over the 53%, however I'd take any of them if the facet pattern is right. DW has a preference for the 50% table, so now I know what I'm looking for! =)2

Next up is what are the ideal Crown and Pavilion angles to go with these facet patterns.
 
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