LIGHTING APPLICATIONS FOR PROTECTIVE COATINGS
THE LED ADVANTAGE
Dr. Michael S. Kralik
Western Technology, Inc.
Bremerton, WA
Abstract: The use of advanced LED (Light Emitting Diodes) lighting for protective coating
applications provides a significant improvement in the efficiency of the process. Better surface and
area visibility improves job performance and is critical for compliant coating application, and provides
a better work environment for the technicians applying the coat.
Introduction
In order to efficiently and safely apply protective coatings to surfaces, consideration must be given to
the light source used. The environment in which the coating is to be applied, such as in darkness or
light, the color of the coating or the color of the surface, the particle size of the application, the ambient
air particulate content, or even the safety gear required all play a part in how you see the job and the
type of light required to effectively prepare a surface or apply a coating. New high efficiency white
LEDs facilitate the most efficient coating application and energy saving process.
History
From the first electrically energized light in 1809 to modern day LEDs, man has been on a quest to
light his surroundings more efficiently. It is really only in the last few years however that modern day
technology has resulted in a practical industrial solution to the problem of vision in otherwise poorly lit
and shadowed work areas. These difficulties arise because all too frequently the area in which light is
required cannot be illuminated adequately by traditional lighting technologies. The result is poor
surface preparation and coating applications with time lost on the job as reworked surfaces.
Using older technologies, compensation for poor vision is often answered by bringing in more lighting
equipment, more power supplies, and more cables and stands. While this may enhance the light in the
area of application, it becomes very cumbersome to maneuver all the equipment required and
expensive to operate. If one uses standard incandescent light bulbs to do their job, at least they’ll stay
warm, since 90% of the power used is emitted as heat with only 10% converted into light on the job.
Over time, workmen have become accustomed to the dull color of the light from these bulbs.
Remember what it’s like when you walk into the sunlight and you are almost blinded, or return again
into the darkness of the workspace and can’t see, even with the light on, until your eyes adjust again to
the darkness? There is a better way: The LED Advantage.
Lighting Application Highlights
The human eye has primary light receptors called cones and rods. Biologically, the eye processes light
in different ways based upon the environmental light conditions we are in. At night, we use primarily
the rods and see in degrees of grey, while in brighter conditions, color is perceived with activation of
the cones. The human eye is most sensitive to green electromagnetic radiation having a frequency of
555 nm. This green light is the standard by which all other illumination is based for human perception
and it’s interesting that the sun has its primary emission in this same region of the spectrum. The
Unified System of Photometry has been established to address the effects of visual perception of light
based upon the time of day and the light used. Interestingly, “cool” white light sources, like the White
LED have been found to improve visibility in nighttime conditions while also reducing operating costs,
unlike the use of traditional yellow colored sodium vapor lamps.
The lumen is a measure of the power of light perceived by the human eye; and the ratio of lumens to
power (watts) is the efficiency with which the light bulb, LED, or other source converts electricity into
visible light. Since the eye is most sensitive to 555 nm green light, it has been determined that 683
lumens per watt corresponds to 100% efficiency of light and all other emitting light sources are
compared to this standard.
LEDs were first practically developed in 1962 having the classic red color, but being only slightly
more efficient then a standard incandescent bulb. These early LEDs only had an efficiency of 20
lumens per watt. More recently, however, LEDs have greatly advanced with colors available ranging
across the visible spectrum including IR and UV emitting diodes. Current technology has made it
possible to create high bright LEDs with brilliant white color due to the composite emission spectra of
violet, blue, indigo, green, yellow, orange and red transmissions. These cutting edge white LEDs are
at the 200 lumen per watt range and increasing, which is double the efficiency of Metal Halide, High
Pressure Sodium, and Fluorescent lamps, and twenty times the efficiency of an Incandescent light
bulb.
Currently, LEDs offer stability of light that other sources cannot provide. Due to the solid state nature
of the design and efficient generation of the photons over the emission surface, LEDs are very bright,
light weight, compact, long lived, provides instant illumination, and are extremely shock resistant.
Compared to incandescent lighting, if you drop an LED light, a filament won’t break, a bulb won’t
burst, and you don’t need to worry if the bulb is going to burn out in the next five minutes. Thus, LEDs
provide both the durability and visual answer to many extreme lighting conditions that predecessor
lighting technologies just can’t. Working in hazardous locations like Class 1 and Class 2 environments
requires equipment with safety fundamental in its design. In these dangerous and visually restrictive
areas, light is at a premium. In painting, coating, and blasting operations with almost immediately
impair vision, incandescent and fluorescent light just can’t deliver the safe, size restrictive illumination
required for the job. Compliant explosion proof LED luminaries, however, are significantly brighter
and more durable, offering the operator lighting solutions which improve working conditions.
In numerous applications, the light cast on the surface must be able to enhance perception by the
human eye. Recent research has shown that the psychological impact of lighting in the industrial
environment should be an important consideration, as all too frequently “luminances in industrial
settings tend to be low, giving the overall environment a cave-like appearance. Although … lighting
can provide the required quantity of light on the work surface, it does little to address other design
issues including the psychological needs of the industrial worker.”1 Thus, if the light transmitted to the
surface is absorbed or if surface irregularities cause light scattering such that reflected light never
makes it to the eye, then perception is diminished resulting in difficult if not impossible working
conditions and create adverse psychological impact. In the coating application arena, light must be
“tuned” to match the environment of application. A color rendering index (CRI) is used to facilitate the
“tuning” of light to the surface, so as to visually perceive the surface, as required, to best perform the
job. The effect of “tuning” the color of the transmitted light from the source to match the surface of
coating application allows for the worker to accurately see the color of the surface under sunlight or
natural conditions. Frequently, the surfaces to be coated are very disruptive to reflected light, because
of corrosion or light absorbing base coats. In these cases, the primary requirement for visual
enhancement of the surface is efficient high bright white light as is provided by new generation white
LEDs. Another direct illuminating enhancement may be obtained by control of the emission light
source beam angle, where a more focused light can provide greater illumination of a smaller surface
area. Base coats may also be visually enhanced by the addition of spectral emissions from the source
via illuminated UV pigmented substraits to bring a radiant glow to the surface.
In conclusion, all lighting applications in general and in the work environment in particular are
becoming brighter, safer places. There is little doubt that constantly advancing LED technology will
soon dominate and illuminate your workplace.
1. “Psychological Preferences for Industrial Lighting,” G.J. Subisak, PE, C.A. Bernecker, Phd, FIES,
Lighting Research & Technology, SAGE Publications, 2010
General References:
2. NAHB Research Center, Inc., 400 Prince Georges Blvd., Upper Marlboro, MD 20774
3. U.S. Department of Labor, Occupational Safety & Health Administration, “Hazardous (Classified)
Locations, 200 Constitution Ave., NW, Washington, DC 20210 (2010).
4. The IESNA Lighting Handbook. 9th Edition, 2000. Chapter 4. The Illuminating Engineering Society
of North America. 120 Wall St., Fl 17, New York, NY 10005
5. Method of Measuring and Specifying Color Rendering Properties of Light Sources. CIE Publication
No. 13.3, 1995. CIE Central Bureau, Kegelgasse 27, A1030 Vienna, Austria.
6. IES Color Committee. “Color and the Use of Color by the Illuminating Engineer.” 1962.
Illuminating Engineering 57(12):764-776.
7. Wyszecki, G. and Stiles, W.S. Color Science: Concepts and Methods Quantitative Data and
Formulae. 2nd Edition, 1982. New York: John Wiley.
8. United States Department of Commerce. National Bureau of Standards. Color: Universal Language
and Dictionary Names. NBS Special Publication 440, 1976. Prepared by Kelly, K.L. and Judd, D.B.
Washington: U.S. Government Printing Office.
9. Merik, Boris. Light and Color of Small Lamps. 1971. General Electric Co. Miniature Lamp
Department, Nela Park, Cleveland, Ohio.
10. Stimson, Allen (1974). Photometry and Radiometry for Engineers. New York: Wiley and Son.
11. Grum, Franc and Becherer, Richard (1979). Optical Radiation Measurements Vol 1. New York:
Academic Press.
12. Wyszecki, Günter and Stiles, W.S. (2000). Color Science - Concepts and Methods, Quantitative
Data and Formulae (2nd ed.). Wiley-Interscience.
13. Cree, Inc., Corporate Communications,
http://www.cree.com/press/press_detail.asp?i=1289396994146.