Friday, October 26, 2012

Fluorescence, Lighting & Color-Grading Diamonds: Time To Re-Examine Its Impact and The Need For Change!

A few years ago, the Accredited Gemologists Association (AGA) organized a lighting task force that investigated the impact of lighting on the grading of fluorescent diamonds. Debate ensued, there was some positive impact, but then the discussion abated and little was done. The time has come to revisit this important topic.

Whether or not a diamond fluoresces, whether or not it is a good thing or a bad thing, and how it affects what consumers are getting and paying, are all issues the trade needs to address. Fluorescence is probably the least-understand of all the factors affecting a diamond’s appearance and value, and confusion and misunderstanding are rampant.

No one can begin to understand or address the issues however without understanding the root of the problem: the lighting used to determine the color grade, and how changes over the past few decades have actually caused most of the problems we have today.

So here is a brief summary of some of the findings from a research project undertaken by the AGA (see for
for the full story and research findings/conclusions).


·      The color shown on many diamond grading reports issued by labs globally indicates the color seen only when exposed to sufficient UV emission to excite a fluorescent reaction.
·      This is NOT the color usually seen when worn by consumers; a fluorescent reaction is usually only excited when the diamond is worn outdoors, during daylight hours. Given today's lifestyles, most people spend most of their time indoors during the day. 
·      This is NOT the color that will be seen when worn at night, whether indoors or outdoors.


·      UV emissions should be eliminated from the lighting in which diamonds are being graded because failure to do so results in over-grading of diamonds with "medium," "strong," and "very strong" blue-fluorescence--which account for close to 10% of all diamonds sold

·      UV emissions should be eliminated from the lighting in which diamonds are being graded because failure to do so results in under-grading of the inherent body color – the color most often seen when worn today – in yellow fluorescent diamonds. 
         Blue and yellow are the two fluorescent colors most often present.  Today, diamonds that fluoresce yellow will show their inherent – and whiter – body color in most environments in which diamonds are worn today; and in outdoor daylight, when fluorescence is stimulated, yellow diamonds often look more fiery and possess a “warmer” color, that may be desired by many diamond buyers.

·      Over-grading results in over-pricing, even with discounts. The time is not far away when this will be the center of another media exposé charging consumer fraud.

·      Grading in a UV-free lighting environment will provide the color that best reflects the color most often observed, and as was done historically, is in the best interest of consumers.     

·      Diamond grading reports that indicate the "stable" color of the diamond as its grade (that is, when no fluorescence is excited,) with a comment that the diamond may look whiter in some lighting environments will remove the negative association now connected with fluorescent diamonds.
             A strong negative association to fluorescent diamonds is pervasive because of information on the internet and elsewhere. Retailers already see consumer avoidance because consumers believe there is "something wrong" with them, and that prices are inflated for what they are getting.  Currently prices are too high because the price is based on an inflated color-grade. Grading the inherent body color (the color seen when the diamond’s fluorescence is not excited) will eliminate over-grading and over-pricing, and with this we will also see a reversal of the negative bias.

             In summary, fluorescence in any fluorescent diamond is not being excited when it is worn in most indoor environments--which is where most people see their diamonds, most of the time, given today's life styles.
             Regardless of indoor lighting conditions, there is insufficient UV emission to stimulate the fluorescent response of a diamond. Just think about it: if indoor lighting produced enough UV emissions to excite a fluorescent reaction, and we exposed to them all day, every day, we'd all be dying from cancer!
        The color indicated on a grading report for a fluorescent diamond graded under UV emissions is not always representative of the color seen outdoors.  Sometimes the color is even whiter than indicated, even when the grade on the report is "D"; a couple diamonds in the AGA study that had been graded D and E actually appeared “light blue" oudoors in daylight!          [This results from a number of variables affecting the intensity of the UV radiation to which the diamond is being exposed – which is affected by such variables as time of day, altitude, air pollution, and so on – and the strength of the diamond’s fluorescent reaction. Thus, the fluorescent reaction can be stronger or weaker than the conditions present in the diamond-grading light unit under which the color was graded.] 
            Industry organizations continue to argue about this, but the science is irrefutable. There are insufficient wavelengths of UV to stimulate a fluorescent reaction in fluorescent diamonds when worn indoors; regardless of whether or not the room is flooded with light, even daylight, the UV emissions present are negligible at best. When a consumer/retailer is only a few inches from a glass windowpane (even plain untreated glass) the UV is greatly diminished; when only a few inches away from a UV-emitting light source, the same is true.
             And last, but not least, another factor that can't be ignored is that more and more homes and offices are moving away from fluorescent bulbs to LED lighting, which contains insufficient UV emission to stimulate any fluorescent reaction in any stone. This means that any rationale that some have used at one time – however flawed* – to justify allowing UV emissions in a diamond-grading light source will soon be obsolete.

* When indoor lighting moved from incandescent to fluorescent lighting, some believed that the fluorescent lighting present in any indoor environments containing them were sufficient to stimulate a fluorescent reaction in any diamond that fluoresces. Thus, any diamond that fluoresced blue, would look whiter, and any that fluoresced yellow would look more yellow. Thus, it was thought that allowing UV emissions in the diamond-grading lighting units would be more representative of the color that would be seen most often. This flawed logic resulted from a lack of knowledge pertaining to the physics of light.

1 comment:

  1. Wow, getting amazed within your details of fluorescence lightning and color grading of gemstones. Thank you so much for these informative share. Kalpana Srikaanth astrologer | Pancharatna gems Coimbatore | Kalpana Sreekanth