Light destroys art. Some wavelengths are more damaging, some media are more vulnerable to damage, but all curators and conservators face a fundamental conflict between the demands of preservation and the desire to display the objects in their care.
These conflicts come to the forefront whenever a museum must decide which objects to display, for how long, and with what illumination. The recent emergence of museum-quality LED lighting is challenging existing assumptions about the “best” lighting for art objects.
Generally speaking, organic pigments and surfaces are more vulnerable to light damage than mineral-based pigments and surfaces. Ultraviolet light breaks down the chemical structure of organic materials and infrared radiation causes heat damage. Marble and glazed ceramics are nearly impervious to light, while works on paper and early albumen-based photographs are particularly fragile.
As part of a recent renovation, Rob Shakespeare, professor of lighting design at Indiana University and principal designer at Shakespeare Lighting Design, designed a new LED-based lighting installation for the Indiana University Art Museum’s1 Special Exhibitions gallery. He explained that a continuous spectrum with uniform intensity is preferable, for both conservation and aesthetic reasons. Intensity peaks will cause some colors to fade more rapidly, shifting the color balance of the object. Gaps in the spectrum do not affect the actual colors of the object, but do change the colors perceived by the viewer. An ideal light source will deliver the same spectrum regardless of brightness, giving accurate color rendition even under dim lighting.
Incandescent bulbs do not score particularly well on any of these characteristics. Their light includes substantial UV and IR components and has a pronounced yellow hue, generally requiring filters for color correction and to protect the art (Figure 1). Reducing brightness by reducing the power to the filament tends to make the light even more yellow. Filters are expensive, increasing the total cost of the lamp assembly. Furthermore, light that is generated by the bulb but then filtered out represents waste heat, increasing the load on the gallery’s climate-control system.
According to Shakespeare, early LEDs were prone to strong intensity spikes in the blue portion of the spectrum, while poor red response degraded color accuracy (Figure 2). Newer commercial LED lamps combine light-emitting devices with phosphors, which act to smooth out the overall intensity spectrum. Some of the excess blue photons excite the phosphors, causing light to be re-emitted in other parts of the spectrum. In more recent lamp designs, like those used for the IU Art Museum installation, both the emitters and the phosphors have improved, providing a much more uniform spectrum (Figure 3). Dimmable LEDs maintain the same color at low intensity, a significant advantage over incandescent bulbs.
For more detail: LEDs Offer Efficient, Color-Accurate Museum Gallery Lighting