Paint Booth Lights for Modern Paint Types|
Article- September 2011 By Larson Electronics.com
Larson Electronics Explosion Proof Paint Spray Booth Light
Modern paint booth lighting systems have to do much more than simply provide a lot of light. Although providing adequate illumination is certainly important, today’s modern automotive paints are of a more complex design and composition than those used twenty years ago. Manufacturers are now using paints that actually take advantage of certain compounds in order to enhance desirable color qualities and inhibit the less desired. How compounds react with light energy and the color spectrum of that light now play a larger role in the how paint color appears, and paint booth operators must take this into consideration when equipping a paint spray booth with a lighting system. How we perceive colors is determined by three main factors:
An object or material, such as a car, obviously.
A light source, such as a lamp or the sun.
An observer who views the object as it is illuminated.
With paint spray booth lighting, the lamps of choice are generally four to eight foot long fluorescent fixtures depending upon the size of the booth. Fluorescent lamps are the popular choice for several reasons. They provide uniform light coverage, have relatively high output, can be configured over a range of color spectrums and temperatures, and produce only moderate amounts of heat. The choice of lamp types for the spray booth is for the most part dictated by how well the lamp reproduces colors, but is to a lesser extent also influenced by operator preferences. Generally speaking, fluorescent lamps within the higher end of the color rendering index scale are preferable because they produce less color variance and reproduce colors more accurately. The color rendering index, or “CRI” of lamps is a scale which basically denotes how closely the lamp mimics the full spectrum of natural light. Ranging from 0 to 100, the CRI of a typical cool white fluorescent lamp is around 65. For critical applications like paint booths, a CRI of 70 or better is preferable because it more closely mimics the natural lighting that the finish will be viewed under in normal conditions.
In basic terms, natural daylight produced by the sun is in realty a combination of several different wavelengths of light radiation, each of which represents a different part of the light spectrum. When separated into their distinctive wavelengths, we perceive each wavelength as a different color. Although the light spectrum is broad, humans can only see a part of it within the 380Nm to 740 nanometer wavelengths. Since our eyes are attuned to this part of the spectrum, light containing all parts of the visible spectrum in the proper ratios is the best for viewing the true color of objects. When light is skewed heavily towards one end of the light spectrum or the other, it alters how we perceive the color of an object. This is because objects reflect or absorb the different parts of the light spectrum depending upon their composition. One material may reflect most green light, yet absorb a great deal of yellow and red light, thus the object appears green because mostly green light is being reflected back to the observer from the object.
Paint manufacturers have taken these physical properties farther, and now use various pigments and materials to enhance the reflective or absorption properties of other materials to produce colors of exceptional intensity and hue. The problem for paint booth operators is obvious; with such complexities introduced into paint coloration and characteristics, being able to accurately match or reproduce colors is made more difficult. When light hitting an object does not contain a full spectrum of colors, or one color is more dominant than others, the light reflected from the object displays this unevenness as well.
For paint spray booths, the best option is to attempt to produce light that matches the color spectrum of natural daylight as closely as possible. Perhaps you may have noticed in some office buildings or grocery stores that utilize fluorescent lighting, that it objects appear “colder”, that colors are less vibrant, and there is a certain starkness to how everything looks. Well, this is because most lighting used in such places is a compromise between efficiency and light quality, with lamps chosen as much for the cheapness of operation as for how faithfully they reproduce colors.
For spray booth operators, such a compromise is far less practical as the quality of their work is directly dependent upon faithfully rendered colors. Lamps are rated with a CRI, or Color Rendering Index, to denote well they reproduce the color of an object. A scale of 0 to 100 is used, with anything below 60 being considered poor, and anything over 70 being considered good. 80 and up is considered very good and is normally the starting point for close work applications such as bodywork and spray painting. CRI should not be confused with color temperature. Color temperature relates to the apparent color of light and not how much of the light spectrum it encompasses. However, color temperature can be useful if light with a specific color temperature is desired for a special application.
Deciding upon a lamp type for use in the spray booth is not as simple as looking for lamps with the highest CRI and installing them. For starters, and perhaps most importantly, paint spray booths require explosion proof certified lighting that adheres to specific regulatory requirements of protection and heat levels. Lamps with higher CRI’s and color temperatures tend to be of higher wattage, and thus produce more heat than lower rated lamps. Care must be taken when choosing a lamp to make sure that the temperature rating and certification of the fixture is not adversely affected by the installation of certain higher powered lamps. Additionally, the intensity and brightness of the lights to be used should be taken into account. Brighter is not always better, and the idea is to not only come as close to the natural spectrum of daylight, but to do so without creating undue glare or intensity that can make working in the paint booth both uncomfortable and difficult. As bad as too little light can be, too much light, or light of too high an intensity can make it difficult to note details and imperfections and cause excessive eye strain in a short period of time.
Many manufacturers provide fixtures that cover all the bases and provide a good balance between power, safety compliance and color rendering. Larson Electronics paint spray booth lights for example are designed to provide the highest protection possible, but also include lamps intended to provide a good balance between power, efficiency and color rendering. The benefit of such special application fixtures is that there is no guesswork and certification and effectiveness can be expected to at the very least meet minimum standards if not exceed them by a wide margin. Other factors such as coverage and the evenness of illumination are in large part a function of paint booth size, design, and light placement, so little can be done to affect these variables beyond choosing fixtures with good light distribution properties and locating them strategically to reduce and chance of dark spots or shadowing.
With the options available in lighting today, spray booth operators can find themselves able to manage the modern types of paints and coatings being used by automobile manufactures with little added difficulty. One thing that is certain, however, is that if these unique properties are not taken into consideration, the quality of the products that leave the booth could very well suffer.