Lighting is Everything
Jewelry Appraisal Information
Thom Underwood, GG, FGA, ASA, NGJA
Master Gemologist Appraiser®
When I moved my lab to a new location two years ago, I had the opportunity to explore the use of LED (Light Emitting Diode) lighting, as well as improve the use of fluorescent lighting as an ambient lighting option. Setting up my new lab was a lighting challenge that was fun to explore. I share the process to inform and suggest options that others might want to consider. Be forewarned, my comments are not empirical. I have provided technical specifications when I could find them. For the most part, the statements below are simply my impressions from daily use.
After nearly 30 years of appraising, this move to a new location was likely to be my last significant business move. Much of the equipment I had I had bought when I started appraising in the 70's. Additionally, the lighting environment I previously worked in had been developed in a haphazard fashion over the years. So I decided to invest in my next 20 years. I purchased some new equipment (out with the old microscope replaced with a Nikon head/Gemological Products fiber optic body, etc.), constructed a built in desk and counters and researched the best lighting these old eyes could find. Replacing the equipment and designing the built in cabinetry was easy. Optimizing a new lighting environment was a greater challenge.
Ambient Light
For starters, I needed ambient light that was subtle and provided a comfortable environment for clients yet not so strong as to overpower localized grading lights on my working surface. I sublease a small, enclosed office space (approximately 100 square feet with no windows) inside a fine jewelry store.
There are two standard 4 foot /2 bulb fluorescent fixtures in the drop ceiling. Color correcting those lights was made easy by simply replacing the regular fluorescent bulbs with full spectrum ones from Vita-light. However, as you might imagine, this produced far too much ambient light for such a small space and dimmer switches don’t work well on fluorescent fixtures. Not a problem. A quick trip to the theatre supply shop here in town provided neutral density fluorescent tube filter sleeves. One can choose the filter density (by percentage) and color (gray in my case) that you want. Voila – I now had appropriately dimmed full spectrum ambient light.
Localized Lighting
Next, I focused on localized viewing lights. Naturally, much of my work involves diamonds or jewelry containing diamonds. As a consequence, I wanted the primary localized lighting temperature to be from 5,600 to 5,800 Kelvin. I knew that Mike Kellen, a friend and founder of Intellighting, was at that time developing LED lighting fixtures for jewelry store display purposes. We talked and he suggested that I consider LED lighting for my appraisal environment.
LED lighting comes in a variety of color temperatures. The lights I use and have tested range in temperature from 5,000 Kelvin to 5,800 Kelvin as well as a 400 nm UV LED and a pocket flashlight that uses diffused LED's at 5,600 Kelvin. Whew!
I was intrigued but skeptical and asked for some demo lights to experiment with. To my surprise I found the light is delightfully white and at 5800 Kelvin seemingly a perfect color for grading diamonds. But I soon found out that LED lighting is full of 'hot' spots. After all it's not just one nice long glowing fluorescent bulb but rather dozens or even hundreds of small light sources mounted together. After explaining this problem to Mike, he quickly designed a sliding Plexiglas filter that diffused the multiple LED light sources; thereby making any lamp usable for color grading and general viewing.
After months of researching, I decided to mount a 12-inch LED light (Intellighting #1BG) modified for a flexible arm suspended over the desk surface located between my seat and client seating. I wanted to use it to show a client details about their diamond. In fact, I never tire of sliding out the diffuser thereby radically increasing the perceived brilliancy and dispersion of the diamond and watching the clients ecstatic reaction.
One of the things I discovered about LED lighting is that it's not very powerful (think Wattage). To make matters worse when I applied a diffuser, which is always necessary for grading purposes, the resultant light naturally became even weaker! As a consequence, LED lighting requires a close distance to the working surface in order for me to experience adequate light intensity for grading. For example, the lamp I eventually set up on my desk surface is mounted only 5 inches above my desk. That works well for grading as well as the low height allows for comfortable eye-to-eye contact with the client and perfect lighting for the working surface below. Having the light on a movable arm allows me to swing it out of the way, if necessary.
In another location in my office, I use a 24 inch size LED lamp (Intellighting #20CL - they are also twice as wide as my 12 inch lamp and containing many more LEDs) suspended under the shelf. This shelf extends over my general working surface that includes, among other small equipment, my microscope, a Gran colorimeter and a standard diamond light box (GEM Diamond Lite) which I have retained as yet another grading light environment. This implementation provides me a soft white light that is a bit too weak for diamond color grading on it's own but great for such functions as measuring and general viewing. For the most part, I leave all the lighting mentioned above on throughout the day. However, occasionally I turn them on and off to alter my grading environment to the task at hand.
Microscope Lighting
Some time after I had installed, worked with, and become enchanted by my two primary LED lights, I decided to replace the fluorescent overhead lamp on my microscope. Jeff Wildman at Gemological Products helped with the logistics of mounting a 6-inch LED lamp (Intellighting #65EXL) running at 5,800 Kelvin. I have found that using LED lighting with magnification produces higher contrast in the magnified viewing image that I have come to prefer. As a consequence, I use this new overhead light far more than I ever used the old fluorescent overhead on my microscope. Once again, as with all LED lamps, this lamp must be diffused to avoid excessive hot spots in the image.
UV / LED
So why stop there? Mike couldn't help himself (forever the inventor) and Intellighting is now producing a long wave ultraviolet LED lamp (Intellighting #65UVPL at 375nm). I am testing the 6-inch version. As explained to me by Mike, the standard fluorescent UV lamp such as the one you have in your GEM Diamond Lite emits 80% visible light and only 20% invisible UV light.
It is that 'invisible' light that causes the UV glow we grade as fluorescence. On the other hand, the LED - UV lamp is the opposite, emitting 20% visible light and 80% invisible UV light thereby enhancing the perceived UV reaction. Theoretically, under LED - UV lighting you will see more of the fluorescent glow and less of that annoying visible blue reflected light. How many times have you asked yourself 'is that fluorescence that I'm seeing in the gem or is it the blue reflection of the visible light from the UV light source'?
In practice, fluorescence under an LED - UV light appears quite different from what you see under the usual fluorescent UV light. It still requires some discrimination to differentiate between reflections from the LED light source and the fluorescent reaction from the gem. Nonetheless, I have found it useful.
Mostly I yearned to try the LED - UV lamp in a fully darkened environment such as my trusty old oversized UV box from the 70's. I recently experimented with squeezing the LED lamp inside my oversized UV box to provide a completely dark environment. The darkened environment and especially the helpful yellow plastic viewing filter on the top of the UV box seems to completely eliminate the remaining 20% visible blue light that the LED emits thereby showing only true fluorescence in the gem. This is a 'Gerry rigged' solution and requires further experimentation but looks very promising to me.
Note: One would obviously have to readjust ones perceived relative fluorescent scale (none, faint, moderate, etc.) when switching over to LED - UV lighting. I am now evaluating how to permanently mount the lamp inside my trusty old UV box.
LED for Color
So far, using the LED lamps and changing my microscope lighting to LEDs, I had only covered my diamond grading needs. What about colored gems? In fact, what are any of us doing about standardized lighting for color grading colored gems? No matter which gem color grading system you are using, we all know that light temperature (Kelvin) and CRI (Color Rendering Index) have a profound affect on the color we see in a gem (and that's ignoring the phenomena of color change in such gems as alexandrite and garnet). Yet if there is an industry standard for lighting a colored gem color grading environment, I am not aware of it. My goal then was simple. It wasn't to set any lighting standard but rather to find a single lighting solution that would work for me and allow me to declare my lighting environment in my report.
So off I went to pester Mike once again asking for a 'warmer' LED lighting solution that I could use for grading colored gems. I started with the premise that I wanted to use only one light temperature. Even though that might not make every colored gem look its best at least I would be using a single standard light temperature.
After all, I am not selling gems, and therefore not as concerned with necessarily optimizing their beauty as I am with standardizing the grading environment. Surprisingly, Mike didn't banish me to darkness but produced a prototype 6 inch LED lamp that provides 5,000 Kelvin light (currently not in the market). I diffused it like all the others, temporarily suspended a piece of white cardboard from the back of the lamp to provide a viewing background. Voila! I had lighting for color grading colored gems. While I expect others much smarter than myself to eventually refine this lamp or produce other superior standardized lighting for grading colored gems this is the best I have had in nearly 30 years of appraising.
Note: Experimentation has demonstrated to me that one single light may be too limiting for all colored gems after all. As a consequence I am considering using two different temperature lights for differing colored gems. In general, a warmer 5,000K light for the red end of the spectrum and a 5,800K light for the blue end might work. In the end using only one light temperature seems too cruel for grading all gems. This, of course, would need to be explained in the introductory section of an appraisal.
My LED Wish List
I am a sedentary worker and my vision is not a portable one. In the future, I would like to see diffused LED light boxes similar to the GEM Diamond Lite providing a standardized lighting environment for both diamonds and colored gemstones. The same box could be mounted with separate racks of LED's each with the appropriate Kelvin. It also would have separate switches to activate each lighting solution. A controlled lighting environment as provided by a viewing box would provide a fixed light to object distance and more importantly minimize the affect of ambient light on the viewing experience. Additionally, I consider a darkened environment such as a UV box mounted with UV-LED's along with a yellow filter to protect the eyes necessary for proper fluorescence viewing and would like to see that implemented as well.
On the Go
For you appraisers on the go, there is LED hope. I have experimented with Intellighting's pocket flashlight that uses 5 diffused LEDs at 5,600 Kelvin (Intellighting #5LPL) making it ideal for color grading diamonds. I think it still needs an additional diffusion lens to reduce hotspots and glare. Nonetheless, I am impressed with the results considering the amazingly low price. Maybe one of these could be produced using 5,000 Kelvin LED's for use with colored gemstones.
Similar portable UV - LED solutions already exist such as the Intellighting pen light (#UVEL) and key chain light (#UVKC) and even a 'clam shell' like diamond grading unit called Portagrade that includes both white light and UV light.
Conclusion
LED lighting is dependable, durable (projected to last 10 to 20 years) and in many cases portable. It uses minimal electricity making it affordable when evaluated over so many years of service. LED lighting adds a sleek modern aura to my office and has been easy to implement and mount in a variety of situations (under shelf, swing arm, fixed, etc.). As a consequence LED lighting has now become integrated along side fluorescent lighting in my new office providing an optimized grading environment that is both comfortable and practical for me and my client.
Thom Underwood, GG, FGA, ASA, NAJA has been appraising since 1978 and is owner of San Diego Gemological Laboratory and publisher of Quantum Leap Appraisal Software. He does not consider this article the last word regarding gemstone grading lighting and can be contacted through his San Diego Jewelry Appraisal website.