Lighting and Evaluation

[Richard W. Wise]

Not sure where this should go but here it is. Would very much like to hear from Pearl people about their views of lighting.

Lighting and Grading Gemstones Part II

LIGHT UP YOUR LIFE


by Richard W. Wise, G.G.
? 2006


What is the best lighting environment to view gemstones? In part I of this post I discussed the various lighting options and the pros and cons of each. In part II I will write about the lighting some of the world?s foremost gem experts and connoisseurs choose to both view and evaluate gemstones.

Among the experts opinions differ somewhat as to which ?daylight? Kelvin temperature is best but each accepts daylight as the standard. Stephen Hofer one of the world?s most respected authorities on colored diamonds, maintains that 5500K works best for colored stones and 6500K is best for diamonds both white and colored. In his lab, which is dedicated to the evaluation of fancy color diamonds, all grading work is done under 6500 Kelvin fluorescents. C. R. Beesley, President of American Gem Labs in New York, prefers Vitalite a bulb manufactured by The Duro-Test Corporation with a Kelvin rating of 5500. "Most people don't do their homework", says Beesley, "comparing color temperature isn't enough..." Beesley tested more than twenty different light sources in the process of developing his Colorscan colored stone grading system to gauge their actual effect on gemstones. READ ON my blog: GemWise: www.gemwiseblogspotcom.blogspot.com link below:

 

[jshepherd]

I cannot say we have measured anything in Kelvin...

I like a diffused light source, preferably natural. I match all of the Tahitian strands myself, I do it in my personal office with my back to the window. The window is tinted and I pull the shades in such a way a lot of light comes through, but no direct sunlight. I have found this to be the best.

In our showroom we use a combination of full spectrum and halogen. The pearls are shown on white cloth.

 

[Valeria101]

Background color appears to be a rather more common thing discussed about the proper display of pearls - I never knew whether there is some practical pretext for the various traditions in favor of either white (grading), black (commercial) of red (both, for Gulf pearls). Not sure if there is any parallel discussion about gems (something about traditional display of small ruby rough on yellow metal, cited in Ruby& Sapphire?) - just fan facts anyway.