Does Polish Affect Light return?

[eyesoftexas]

I have been to many web sites to educate myself on diamonds more and more. I really did not see too much on how Polish affects light return. My sister’s diamond has a rating of Good polish with excellent symmetry while my wife’s old ring has excellent polish and excellent symmetry. Both are round brilliants of 1 ct. My sister in laws ring has excellent light return while my wife’s old ring leaks light all over.

While I could understand in theory that the smoother surface would allow more light return, the role of polish in the overall light return must be small versus the more important factors of cut (table depth, crown angle etc..). Granted a really poor polish will probably allow a lot of leakage and screw things up visually but I also figured that if it was that important, polish would be incorporated into the cut advisor calculator? I know from first hand visually and ideal scope that my sisters ring with good polish blows away visually my wife’s old ring.

 

[valeria101]

NO!

Even "good" polish is very polished indeed, with nothing obstructing light left in place. I have yet to see any modern cut with less than 'good' (as per GIA's) polish...

 

[eyesoftexas]

Valeria101,
Does this mean that we really should not worry about polish beyond a good polish. Is it worth paying more for excellent or ideal polish?

 

[valeria101]

I can only speeck for myself, but this is exactly what I meant. I would want VG (or better) symmetry in a round just because quite diferent "anymals" get labeled "good symmetry" in GIA terms, but otherwise I would definitely not consider Ex or Ideal symmetry and polish as signifficant assets in a stone with no merit in the light return department. Polish is probably not worth a second thought, symmetry may affect light return and certainly botch that H&A pattern if not good enough (hence the noted preference for VG rather than 'good'). However, symmetry remains - for me - just some extra detail as long as light return is fine.

It may be worth noting that symmetry and polish do depend allot on cutting technology. Old diamonds would almost all be considered o "fair symmetry" these days, "very good" symmetry would have been unusual two decades ago but it is no longer a rarity in rounds. hence the need to define a higher notck: so here comes the 'excellent' and 'ideal' - both a real pain to discern (I think Garry mentioned on some other thread that this is true for professional too).

Just my opinion, of course.

 

[Garry H (Cut Nut)]

Very good quaestion EoT.
I asked an appropriately experianced and well resourced associate in India to run a series of test which he is doing and will present at our Moscow Cut Conference in April. He is well into it.

A also met with the President and 2 senior researchers of GIA in HK last week and asked them if they were aware of any empirical research - neither was.

Finally Pater Yantzer, the AGS Lab Director has told me that he can not 'see' the difference between good and excellent with his naked eye.

So as some other researchers always say
"watch this space"