Eulitz & historical diamond cut studies

[tanalasta]

Does anybody have a copy of Eulitz''s work on the ideal proportions of a round brilliant diamond?

Titled: Die recherische Ermittlung der optimalen Brillanz des Brillanten - Eulitz

There has been a lot of discussion re: the Tolkowsky ideal but I''m wondering from people who have read Eulitz''s work what they think of his (and other) historical works. The reason why I''m asking is that although a lot of studies tend to have proportions that are still reasonably close to Tolkowsky''s work, Eulitz published a stone that favoured maximal brilliance but was actually considered a shallow/shallow. How did Eulitz come up with a ''shallow-shallow'' and what compromises would have had to been made to maximise brilliance? Loss of fire?

A list of proportions and historical studies can be found in the GIA''s publication in 1998 but here is a short summary:
BMark CrnH PavD Table Girdle CAng PAng
American Standard 16.2% 43.1% 53.0% N/A 34.5° 40.75°
Practical Fine Cut 14.4% 43.2% 56.0% N/A 33.2° 40.8°
Scandinavian Standard 14.6% 43.1% 57.5% N/A 34.5° 40.75°
Eulitz Brilliant 14.45% 43.15% 56.5% 1.5% 33.36° 40.48°
Ideal Brilliant 19.2% 40.0% 56.1% N/A 41.1° 38.7°
Parker Brilliant 10.5% 43.4% 55.9% N/A 25.5° 40.9°

Have any of the above been credited or discredited?

 

[starryeyed]

What about depth percentages?

 

[He Scores]

One has to remember that stones listed on a table like this are theoretical. I look at data on many stones and I''ve yet to see a diamond that is 100% round, and each main facet top and bottom is on the exact same angle.

The one stone on that list that deviates from the list with a steep crown angle 41 and a shallow pavillion angle is a model of the old mine cut "two pointer". Whether that data is from that era or not I don''t know since I''ll admit to not seeing the study.

How that stone can be considered a premium stone is beyond this cutter since bottom angles under 39 degrees will display a fisheye.


Bill Bray
Diamond Cutter

 

[tanalasta]

I think that both the ''Parker'' and ''Ideal brilliant'' which have rather unorthodox angles have been discredited as being not as bright compared to the American (Tolkowsky) standard.

I am interested in knowing more about the others though.

 

[Richard Sherwood]

Date: 1/23/2007 7:15:33 PM
Author:tanalasta
Does anybody have a copy of Eulitz's work on the ideal proportions of a round brilliant diamond?

Titled: Die recherische Ermittlung der optimalen Brillanz des Brillanten - Eulitz

There has been a lot of discussion re: the Tolkowsky ideal but I'm wondering from people who have read Eulitz's work what they think of his (and other) historical works. The reason why I'm asking is that although a lot of studies tend to have proportions that are still reasonably close to Tolkowsky's work, Eulitz published a stone that favoured maximal brilliance but was actually considered a shallow/shallow. How did Eulitz come up with a 'shallow-shallow' and what compromises would have had to been made to maximise brilliance? Loss of fire?

Hi Tana. Fascinating topic.

Eulitz's proportions are included in the Russian Moscow State University DiamCalc program, so I can post the proportions here:

59.1% depth
14.5% crown height /// 33.6% crown angle
56.5% table
43.2% pavilion depth /// 40.8% pavilion angle

These proportions actually produce a stone which majors in white light return (brilliiance) and minors in coloreld light return (brilliance). They can be quite beautiful diamonds with amazing white light return, but lacking a bit in colored light return (fire).

 

[Garry H (Cut Nut)]

Mr T you are trying to simplify history.

Ask historians what they think about this?

Tolkowsky for instance is not listed there - but some historians have stolen his lifes work.

And Tolkowsky is the most discredited of those scientists - because his was the best and most enduring work - it attracted the most attention.

eg it has been found the addition of a girdle invalidates the table size, and that his math showed that he choose just one proportion set whereas he should have predicted a range of inverse crown and pavilion proportions as described here http://www.folds.net/diamond/software_help.html by our co poster Jasper, and also on the www.cutstudy.ru Moscow Uni site in an article by our other mathematician engineer poster Beryl (Bruce Harding)

It is easy to discredit. But it may not mean much.
Our Cut Group have discredited GIA''s cut study and grading system. But they still make close to $100 million a year using it.

 

[strmrdr]

Date: 1/23/2007 9:55:12 PM
Author: Richard Sherwood

Date: 1/23/2007 7:15:33 PM
Author:tanalasta
Does anybody have a copy of Eulitz''s work on the ideal proportions of a round brilliant diamond?

Titled: Die recherische Ermittlung der optimalen Brillanz des Brillanten - Eulitz

There has been a lot of discussion re: the Tolkowsky ideal but I''m wondering from people who have read Eulitz''s work what they think of his (and other) historical works. The reason why I''m asking is that although a lot of studies tend to have proportions that are still reasonably close to Tolkowsky''s work, Eulitz published a stone that favoured maximal brilliance but was actually considered a shallow/shallow. How did Eulitz come up with a ''shallow-shallow'' and what compromises would have had to been made to maximise brilliance? Loss of fire?

Hi Tana. Fascinating topic.

Eulitz''s proportions are included in the Russian Moscow State University DiamCalc program, so I can post the proportions here:

59.1% depth
14.5% crown height /// 33.6% crown angle
56.5% table
43.2% pavilion depth /// 40.8% pavilion angle

These proportions actually produce a stone which majors in white light return (brilliiance) and minors in coloreld light return (brilliance). They can be quite beautiful diamonds with amazing white light return, but lacking a bit in colored light return (fire).

I actually like that combo a lot 33.6/40.8.
I love white light return in my RB''s I usually don''t go that far to get a little more fire with something like a 40.8-41.2 with a 34.0-34.5 crown with a 55-57 table.

As far as 33.6/40.48 goes its a good combo for a pendant or earrings where it wont be viewed close and will send very bright white light beams out to attract attention and maybe be less affected by dirt on the pavilion.