The aim of this project is determine the extent to which the range of techniques for illuminating works of art on paper (particularly old master drawings) can be improved or modified to provide a higher margin of safety when applying exhibition illumination guidelines.

Project Objectives
At the simplest level, there are three components that mediate the interaction of light and artifacts: the light source spectra itself, (including filtration, intensity, and duration of exposure); the current chemical states of materials used in artifact construction; and the gaseous envelope that encompasses the artifact. Without touching the artifact or altering its chemistry, project participants are conducting studies to:

• Determine what can be done to further reduce the total energy transferred to the artifact before light levels or color rendering becomes unacceptable for public viewing;
• Extend basic understanding of the range of pigments and dyes that can benefit from the removal of oxygen from the objects atmosphere; (e.g. fading rates, darkening, color shifts, and no effect);
• Determine visitor preferences in low lighting situations, including preferences for color temperature of the lighting source (as described in early lighting research) and determine how to address critical engineering parameters (like the Color Rendering Index) in this and future research;
• Monitor industry development in new lighting sources—including but not limited to the rapidly expanding field of light emitting diodes (LEDs) and other new photonic devices that may be of potential application with the museum setting.

Project Overview
Over the years, guidelines for exhibition lighting have evolved from applying a reasonable but limited set of heuristics (i.e. "rules of thumb") to diverse collections of objects under a few lighting conditions, to managing light exposure under a rapidly growing number of new lighting sources and exhibition design possibilities. It was once inconceivable to openly speculate on acceptable levels of light-induced damage, but today, managing damage over time as part of applied preventive conservation is a familiar and widely-held concept.

For a museum to meet its educational and exhibition mandates, it is necessary to expose works on paper to light. Light exposure remains unique among environmental risks because it can neither be eliminated nor completely controlled. In fact, illuminating a work of art for viewing always involves the transmission of energy to the artifact and the potential for numerous and varied, surface and bulk materials interactions. All these interactions carry some percentage of risk for irreversible change that we may define as damage.

The most common and effective methods of controlling light-induced damage has always been to reduce the overall light intensity, restrict the total time of illumination remove wavelengths of light the human eye is insensitive to, and make sure that, whatever the microenvironment surrounding the artifact, the exhibition lighting does not magnify other environmental risk factors.

When applying light damage mitigation techniques simultaneously to maximize conservation, compromises are necessary—display times are limited, and light levels may be so low that they challenge perception through skewed color rendering and reduced detail. This is a challenge, particularly for older visitors. Thus, having more tools to manage light damage could improve overall management and reduce the magnitude of these compromises.

Last updated: November 2006