Education on the use of the HCA tool for super ideal cut diamonds

[Texas Leaguer]

Sorry still trying to get my head around it!

I have two diamonds.
Diamond 1 is 35/40.8 57% 61.5%
Diamond 2 is 34.5/40.8 56% 62.6%

Diamond 1 is significantly better in performance, it seldom looks dirty and is always edge to edge sparkly.

Diamond 2 has poor performance not long after it’s cleaned, especially on the edges.

Both diamonds have great ideal scope images with no leakage.

@Garry H (Cut Nut) why would diamond 1 be a significantly better performer? It goes against what you have mentioned above?

The CA/PA proportion difference here would not account for a significant performance difference. Optical precision could be at play, but it is more likely to be some difference in transparency. Even diamonds with the same clarity grade can have different levels of transparency, especially in the Si range, due to often subtle differences in clarity characteristics.

 

[Serg]

Sergey do you know what Diamond Enthusiast mentioned? I put these proportions together as recommended proportions early this year.
You have a problem with them clearly.

Perhaps we should run a poll as to how often people clean their diamonds? I imagine PriceScope forum participants clean their diamonds some where between twice and a hundred times more often than most people.

Diamond Proportions

The physics of light-behavior within a diamond are reliably consistent, which means proportions measurements can be useful.

www.pricescope.com

We name these proportion combinations "Sweetline"

Sweet Line in Round Diamonds – docs

Consider two dimensional Ca-Pa variations of the round parameters

docs.cutwise.com

https://octonus-teams.com/wiki/display/HPCDPUB/Using+SweetLine



Originally we showed this relationship between crown and pavilion angles in 1999
http://www.gemology.ru/cut/english/podrobno_4.htm

As I remember, I informed you on the correct range for Pavilion/crown angle ratio (1:4 - 1:5) about 20 years ago, before that you used to use 1:2 ratio. Do I recall this correctly?

Diamonds along the Sweetline have almost identical optical properties. I doubt that consumers can see any real difference in Fire and Brilliancy between P 40.8 Cr34.5 and, for example, with either P40.5 Cr36 or P41.5 Cr31. I do not see any grounds for your statements about more Fire or Brilliancy in this proportion range.

So, I obviously do not have the problem you have mentioned.

 

[Serg]

This is from a GIA article - tried to find it but failed:

A light ray striking the inner surface of a diamond is reflected back into the diamond because it strikes outside of the critical angle. Right: Notice how the same light ray, striking from the same angle, is now able to escape (transmit) through the pavilion facet because the oil on the surface has changed the critical angle.

The problem is when you look at the outer facets on a round slightly deep diamond your line of sight goes into the diamond, bounces of the same side pavilion facet and then leaves and is swalloed up by the oily greasy gunk on the opposite side pavilion. A slightly shallow diamond suffers less of this effect:

Photos i took recently of a clients dirty diamond ring - you can see it is mostly the outer facets that suffer.

The efforts in adjusting Tolkovsky parameters for dirty stones can be compared with recommendations on how to finetune a Nascar vehicle to take part in Dakar rally. If you are serious about games in dirt it is better to choose another league from the very beginning.

In fact, any kind of +/- 0.5 % angle change has less impact on diamond performance than another layer of dirt. Needless to say that dirtiness should be measured for true scientific approach and accurate analysis of dirty diamonds performance. Then it will be possible to plot an integral chart of performance as a function of dirtiness and angles.

I believe the majority of the PS members are seeking true scientific understanding of diamond performance phenomena. From this perspective the promoted here dirty logic is unacceptable for professionals and it is crucially misleading for consumers who trust expert advice. Those who choose shallow diamonds( Like P40.3 Cr34.5) will wear relatively dark stones when they decide to clean them.

 

[Texas Leaguer]

The fact that a buildup of dirt and film on a diamond actually changes it's refractive index/critical angle is an interesting and important fact. That some stones may perform better than others when dirty is a worthy debate.

However, I don't think anyone is arguing that any diamonds look better when dirty. So always keep your diamonds clean!

My rule of thumb is to clean your diamonds somewhere between as often as you clean your clothes and your car. Never let the film build up and bake on, otherwise you may not be able to get them clean without a professional cleaning.

And always clean your diamonds after taking part in a Dakar rally.