Crown Angle (5.10)
The original ideal angle for the crown is 34.5°. Here again, the major gem labs do agree that slight variations from this angle will still produce a well-cut diamond. This angle was designed to provide the final escape route for the reflected internal light so that the dispersion and brilliance could be viewed. It was also important to provide an angle great enough for light to enter and exit from more diverse directions. These diverse directions are multiplied when the star and upper girdle facets are added. But the angles could not be so steep that the light reflection from the pavilion traveling back up to the crown would be reflected back (trapped) into the stone. At 34½˚, the angle of dispersion is at its greatest. At 30˚ one would have to look in a more parallel direction to the table of the diamond to observe its dispersion. At 34½˚ the diamond could be tilted further away from parallel and still portray the dispersion of a well cut diamond.
