The Effect of Blue Fluorescence on the Colour Appearance of Round-Brilliant-Cut Diamonds.

Bouman, Marleen; Anthonis, Ans; Chapman, John; Smans, Stefan; De Corte, Katrien

To better understand the influence of blue fluorescence on the colour appearance of (near)-colourless (D-J) diamonds, carefully selected sets of round-brilliant-cut samples of varying fluorescence intensity were observed at HRD Antwerp under lighting conditions that simulated four different environments in which diamonds are commonly viewed: Outdoor, Indoor, Grading and Office lighting. Each of these environments contained a different level of long-wave UV radiation (emitted from LEDs) combined with daylight-equivalent fluorescent lighting (filtered to remove its UV component). Diamonds were presented to observers in both table-up and table-down orientations, and the effect of blue fluorescence on their colour appearance was determined by observing them with and without the UV component of the lighting and also by visual comparison with non-fluorescent master stones in each of the four lighting environments. The observers consisted of experienced graders, industry participants and consumers. For colours of J and higher, the simulated Outdoor lighting (which contained the greatest UV component) elevated the grade of diamonds with strong and very strong fluorescence to D-E colour when viewed table-down. The table-up effect was less pronounced. The UV content of the Office lighting was insufficient to produce any observable effect, even for diamonds with very strong fluorescence. HRD Antwerp's laboratory performs colour grading in an environment that lacks significant UV radiation.

DIAMONDS; GEMS & precious stones

Journal of Gemmology, 2018, Vol 36, Issue 4, p298

1355-4565

Academic Journal

10.15506/JoG.2018.36.4.298