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HCA - Defining the Beauty and Desirability of Round Brilliant Diamonds

Fire or Dispersion

It is commonly and correctly believed that diamonds with steeper crown angles and smaller tables have enhanced fire. Believing this makes objective observation based study of the nature undertaken here was somewhat difficult. However the discovery that shallow crown angled diamonds display enhanced fire challenged the preconditioning notion.
 
I acknowledge that fire is the most subjective and least reproducible of the four factors presented here. Never the less we have made many loosely structured comparisons with actual diamonds in various lighting conditions and a variety of observers.
 
The first of these two sets of charts show a selection of crown and pavilion proportion combinations with the virtual fire tool from the MSU / Octonus website www.cutstudy.com/cut/english/comp/scint1.htm. The second chart has had a head shadow effect subtracted.
 
Because HCA is concerned with the face up view, removal of the central section of the image effectively reproduces the potential for fire should a ray of light fall on the diamond from the same direction as one of these areas of a firey flash. Many people find this concept rather difficult to understand, and it is very difficult to explain. It may help to imagine that we are considering the ray of light to be going in the opposite direction. Therefore the more firey flashes on the imaginary screen, the more potential fire could be displayed. However we must always remember that excessive brilliance will drown out potential fire.
 

Figure 14. These grids show fire returned to a screen placed between diamond and viewer. The virtual diamond is illuminated from a single light source from directly above the diamond. The central area has been removed from the second set, simulating the effect of a 21° head shadow. To use this tool for Consider the reverse situation - if illuminated with a beam of white light from the same direction as a burst of fire, then an observer positioned directly above the stone would see the same burst of fire.
 

Figure 15. Comparative fire scores estimated for each diamond on grids for crown and pavilion angles.
 

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