Museum and Art Gallery Lighting RP-30-96
is among the most respected reports about the display and lighting of artwork in museum and art galleries. It is a reference for architects, engineers, lighting designers, and museum curators.It is published by the Illuminating Engineering Society of North America and is available at their web site. The report is quite complete with recommendations and discussions concerning the effects of exposure to light and heat. The report says that both light and heat can seriously damage oil and watercolor paintings, and protecting works of art from the natural aging process is something to be taken seriously. An unprotected a masterpiece in the sunlight can fade, crack, oxidize and fade beyond recognition. The key to prolonging life of artwork is the stabilization of temperature and humidity, and minimized the exposure to radiant energy or light. Light is radiant energy, and exposure to light gradually causes permanent damage to many museum objects. When radiant energy strikes the surface of artwork some portion of that energy is absorbed. This can promote two distinctly different processes that can cause degradation of the painting. Radiant heating effect and photochemical action. Typical picture lights with bare exposed incandescent bulbs provide high light levels up at the top and produce a temperature rise several degrees higher than the rest of the painting. The report says raising the temperature speeds up all chemical actions, including oxidation, but radiant heating has other deleterious effects. The surface will expand relative to the body of the object, and moisture will be driven from the surface material. The effects of this cycle can be devastating, particularly in materials have differential expansion coefficients, or where surfaces are composed of different materials, such as pigment and/or varnish over a substrate. The symptoms are surface cracking, lifting of surface layers, and loss of color. The symptoms of photochemical action may include fading or darkening of colors, yellowing, embrittlement, loss of strength, fraying of fabrics, and even quite dramatic color changes of some pigments.
The report makes a special note: All lighting should be filtered to eliminate all ultraviolet radiation (400 nm and below) See products page for test report of my new UV filter. They go on to recommend maximum light levels and the maximum hours of exposure per year depending upon the type of material on display. |
| Types of Materials | Maximum Illuminance | Lux-Hours/Yr (Neither value should be exceeded) |
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Highly susceptible materials: textiles, cotton, natural fibers, furs, |
50 lux | 50,000 | 50,000= (50 lux) x (8 hours per day)x (125 days per year). Different levels {higher or lower) and/or different periods of display (4 hours for 350 days) may be appropriate, depending upon material. if in doubt, consult a conservator. |
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Moderately susceptible materials: Textiles with stable dyes, |
200 lux | 480,000 | Note: 480,000 lux/hrs/yr = (200 lux) x (8 hours per day) x (300 days per year). Lower levels may be appropriate, depending upon material if in doubt, consult a conservator. |
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