Don''t exclude a thin girdle out of hand: This is where the skill of the setter is as important (more in fact) as the cut of the diamond. Thin, medium and stk are all acceptable girdle averages and a setter worth his salt can set them equally well. In fact, if a girdle average is medium and the range runs from very thin to medium there may be nothing to worry about: Corners are naturally vulnerable on princess cuts, but the ''very thin'' as a range indicator only may imply a single extremely small spot (or perhaps an indented natural) which is nowhere near the vulnerable corners and no cause for worry. Determining vulnerability must be done on a case-by-vase basis.Date: 1/17/2007 10:26:48 AM
No. A Princess is a fancy cut with different crown/pavillion and multiple combinations.
There are some old cut-charts with the basic proportions that a Princess should have but there is too much interplay between the different facets and angles to go by numbers alone. Hence, if you want to play it super-safe to know you have an ideal Princess - you need an ASET (or at the very least an IS) or preferably - one that has been graded by the AGS as 000 ideal.
A princess should have a medium or slightly thick girdle as the corners are more prone to chipping.
I think this is intersting Paul - could you give me the other two angles and tables size - because according to the AGS charts there is not many good matches around that zone for at least the 65% table size.Date: 1/17/2007 11:47:10 AM
My reply might surprise you, but I think that princess-cuts follow the same rules as rounds. After all, it is the same material, diamond, and it is the same light entering from the environment, isn''t it?
The problem lies in notation and in perception, though. I will keep my maths as simple as possible.
Let us look at the pavilion of a round. We agree that we should have good symmetry and a pavilion-angle of around 41°, thus resulting in a pavilion depth of around 43%.
In a princess-cut, the P2-angle, going from the point to the culet, should also be around 41°. But because the depth of a princess is not a factor of the average diameter (like in rounds), but of the smallest diameter, this changes the depth-percentage. Since the facet goes from the corner to the culet, the depth is about 43% of the longest diameter (from point to point). In gemology however, we use the smallest diameter as a reference, and suddenly, the same pavilion-angle causes a depth of slightly over 60%. So, same rules, same angle, but different notation.
In the same way, I like a crown angle in a princess-cut, which is around 34°. Reminds me a lot of what I like in a round.
They have become different animals, however, because the notation of the proportions is different. If you have a princess with a total depth of 63%, this would be under 55%, if we would calculate it in the same way as in a round. Are you sure that you would want to have a round with only 53%-depth?
Sorry, I am beginning to ramble. I hope that you caught my point. If not, ask again, and I will try to clarify.
I agree the pvilion is always most critical.Date: 1/22/2007 11:23:21 AM
How about 60 table, pavilion 59-41 and crown 34-28?
You are right and wrong with your comment on the crown and french-corner. This corner-facet is indeed technically comparable to the main crown-facet. But their surface is in comparison very small.
Stars for instance, in a round, have an angle of around 23°. So, maybe an second crown-angle of 28° in a princess offer more possibility of fire, provided the other angles are OK?
Anyway, in all comparisons, the importance of the pavilion is much higher than that of the crown.
A round diamond needs only table, crown and pavilion angle to tell if it is well proportioned - there are only minor influences from other facets that have about 1 in 100 chances of being bad.Date: 1/23/2007 4:25:53 PM
So, most of this discussion is over my head (*whoooosh*) but could either Garry or Paul deduce a desired pavillion angle/crown angle combo? Or is this kind of info useless?
Sorry...it''s hard to wrap your mind around the above concepts.