Bow Tie on an Oval

[KSmith]

In looking at a few oval diamonds this weekend we saw a wide variety of bow ties. Some diamonds that looked great on paper, yet still had a bow tie that was far too noticable. It really proves the point that looking at the actual diamond itself is very important.

I read the article on Pricescope by David Atlas about independent appraisers and would be curious if an appraisal would include something talking about that? I am guessing that the output is pretty similar from appraiser to appraiser, but do any or all include something that tells you exactly what aspects of the diamond cause it to be worth more or less?

 

[pricescope]

I think David will discuss these issues with his clients. David is on vacation till March 3rd but his lab is working.

Some visible bowtie is normal for oval, marquise and pear. It is reflection of the observer head. Check it by viewing the stone thru small hall in white paper sheet - bowtie should be gone.

If there is now bowtie at all, diamond is leaking too much light.

 

[abbott]

When you say look thru a small hole on a sheet of paperin order to evaluate the bowtie of an oval .... This might be a silly question but how large should the hole be? Is the hole of a standard piece of notebook paper about the right size or should it be smaller?? Thanks

 

[Garry H (Cut Nut)]

Big enough to see through - a peep hole.
The bowtie will go white (there will also be not scintillation at all.

The problem with bow tie 'grading' is there is no industry standard - the bow tie is bigger if you view the stone closer up and if you have a bigger head and blacker hair, or a big hat on.

 

[Rook]

Leonid, you said;


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If there is now bowtie at all, diamond is leaking too much light.

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???

Could you go into more detail and explain this for me. I always though that the less bowtie the better? What is the relationship between bowtie and light reflection/reflaction and light leakage?

Thanks

 

[Tarams]

Would you mind explaining that "peep hole in the paper" process more clearly?

Thanks!

 

[Garry H (Cut Nut)]

http://www.diamond-cut.com.au/13_scint.htm
for an explanation