1. Task Force Color Grading Research – Summary Results
True Body Color – The color of a diamond observed when its fluorescence is not stimulated.
Reference Artificial Lighting Environment – For purposes of color grading the 25 test diamonds, the artificial lighting environment considered representative of determining a diamond’s True Body Color was situated approximately three feet (91cm) beneath an overhead lighting fixture, which consisted of four 32Watt Philips fluorescent bulbs (F32T8), daylight color, enclosed by a clear plastic diffuser.
Summary of Test Results:
Diamonds with GIA Report
VST: Reported color grades were 2.0 to 4.0 grades overstated compared to color grade test results.
ST: Reported color grades were 0.5 to 2.0 grades overstated compared to color grade test results (note: the 0.5 difference related to a diamond whose fluorescence was re-graded and determined to be MED).
MED: Reported color grades up to 0.5 grade overstated compared to color grade test results.
FT: All grades within 0.25 color grade of testing tolerance.