New Mineral Named After GIA’s John Koivula
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 Post subject: Re: What is the ideal baguette cut?
PostPosted: Mon May 13, 2019 10:04 am 
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Duncan Miller wrote:
Shifter55 wrote:
This is what those angles give me when rendered, all tiers on the top and bottom were cut to equal size. Feels like one too many crown tiers to me, but there's plent of scintillation in the table (and fisheye)!

What you have rendered is not a baguette cut, but an octagonal step cut. A diamond baguette is a rectangle with sharp corners (vulnerable to chipping).


Hi Duncan,

The poster of the drawing is not the original poster. I think he was trying to create ideal performance in a step cut stone, not a baguette. Therefore he used an octagonal symmetry the same as an RBC.


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 Post subject: Re: What is the ideal baguette cut?
PostPosted: Mon May 13, 2019 2:15 pm 
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I agree with Duncan. The octagonal step-cut does not appear to be relevant to the original question.


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 Post subject: Re: What is the ideal baguette cut?
PostPosted: Mon May 13, 2019 4:39 pm 
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I can see the logic of the octagonal step cut. If you look at RBC Ideal proportions it serves as the basis for all of the other modified brilliant cut diamonds, Oval, pears, marquise, ect. are just deformations of the original round.

If we could establish a best performance for a step cut on a perfectly symmetrical stone, that cut could be deformed in the same manner for the other shapes in a step cut.


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 Post subject: Re: What is the ideal baguette cut?
PostPosted: Mon May 13, 2019 5:32 pm 
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Ideal "style" cuts although feasible for round stones (to a lesser extent, gems having an equi-dimentional diameter) do not apply to variations of round, brilliants.

Marquise, oval and pear shapes have different length to width ratios...like baguettes.
Therefore, mathematically, each variation would have to be individually computed based on the dimensions of the rough and desired prospective yield.


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 Post subject: Re: What is the ideal baguette cut?
PostPosted: Mon May 13, 2019 7:25 pm 
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I have heard that GIA is working on cut grading for fancy shapes. One day we actually have "Excellent" cut grades on them. One thing I am sure of, yield will not figure into the grade.


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 Post subject: Re: What is the ideal baguette cut?
PostPosted: Mon May 13, 2019 7:56 pm 
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Duncan Miller wrote:
What you have rendered is not a baguette cut, but an octagonal step cut. A diamond baguette is a rectangle with sharp corners (vulnerable to chipping).

Here's a square, the only reason octagons are used is because my own folder of step cut proportions uses the outline. Overall, the pattern does not change much, and the octagon can be seen as a more compressed version of the square cut's reflection.


Attachments:
WaterMeyerSquare.gif
WaterMeyerSquare.gif [ 36.31 KiB | Viewed 259 times ]
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 Post subject: Re: What is the ideal baguette cut?
PostPosted: Tue May 14, 2019 1:03 am 
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I received a large parcel of matching baguettes from a major supplier (not Stuller) a bit ago, beautifully matched and cut with 5 - 7 degree step separation on the bottom. No waste, great brilliance, just GREAT!

We aren't talking colored gems here, so we can't use the excuse of color saturation to justify those deep, off-centered pavilions. It is just plain greed.

Here is the ASC text for a 5 degree step, in case you have GemCad or Gem Cut Studio and know how to use this information.

Copy the text below, open MS Notepad, paste it in the document, and save as "All Files (*.*)" rather then "Text Documents (*.txt)" in file type, and name something like Baguette.asc . The ".asc" part of that is important to be able to open it in the design program.

******************************************

GemCad 5.0
g 96 0.0
y 2 y
I 2.42
a -90.000000 0.55555556 72 24
a -90.000000 1.11111111 96 48
a -51.000000 0.47807633 24 72
a -51.000000 0.90982408 96 48
a -46.000000 0.46946709 72 24
a -46.000000 0.86910031 96 48
a -41.000000 0.48186848 72 24
a -41.000000 0.84634572 96 48
a 47.000000 0.38479052 24 72
a 47.000000 0.79109813 96 48
a 37.000000 0.33318656 24 72
a 37.000000 0.66752824 96 48
a 27.000000 0.30134208 24 72
a 27.000000 0.55355902 96 48
a 0.000000 0.19841662 96


Attachments:
Bag 5b.JPG
Bag 5b.JPG [ 31.35 KiB | Viewed 246 times ]
Bag 5.JPG
Bag 5.JPG [ 30.11 KiB | Viewed 246 times ]

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 Post subject: Re: What is the ideal baguette cut?
PostPosted: Tue May 14, 2019 4:12 am 
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abeck wrote:
Here is the ASC text for a 5 degree step, in case you have GemCad or Gem Cut Studio and know how to use this information.

Thank you. Now we can compare performance of these angles with those recommended by Basil Watermeyer, with three equally sized tiers on crown and pavilion, viewed from above or below. Watermeyer recommends shallower angles for both pavilion and crown, which make for a slight improvement in overall performance with GemRay, but of course also a slightly shallower and lighter stone. He has an interesting paragraph on the history of the culet angle for emerald-cut diamonds, concluding that the "37 degree angle is now accepted as the correct angle" (page 295). Presumably this holds for any rectangular step-cut diamond.


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 Post subject: Re: What is the ideal baguette cut?
PostPosted: Sun Aug 04, 2019 12:52 pm 
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Shifter55 wrote:
I think Long & Steele's baguette is proportioned to make the mains equal in size to the table, and you can find a lot of emerald designs proportioned to so the step tiers are of even width when viewed from the bottom.


Oddly enough, Long & Steele's baguette is neither exactly.

Which one do you think is better? Making the mains equal in size to the table or making the step tiers of even width when viewed from the bottom?

If table width is HALF of the baguette's width it's possible to achieve both simultaneously. Is that the way to go?


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 Post subject: Re: What is the ideal baguette cut?
PostPosted: Sun Aug 04, 2019 1:05 pm 
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1bwana1 wrote:
Finally size the facet tiers in classic emerald cut relationship.


Can you tell me what that is? Where can I read more on this?

Mainly interested in how to choose pavilion angles, total ideal pavilion height and how many degrees between pavilion steps would be ideal?


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 Post subject: Re: What is the ideal baguette cut?
PostPosted: Mon Aug 05, 2019 10:22 am 
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VFA wrote:
Can you tell me what that is? Where can I read more on this?

Authoritative books on diamond cutting, by Basil Watermeyer. https://www.abebooks.com/book-search/author/basil-watermeyer/


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