To what extent can the range of techniques for illuminating works of art on paper be improved or modified to provide a higher margin of safety to light-sensitive artifacts and improve the aesthetic viewing experience when applying exhibition illumination guidelines? The GCI's Museum Lighting Research project aimed to explore this question through a range of research that included:
Investigating use of a three-band filtered light source with thin-film multi-coatings to reduce the overall radiant energy transfer to works of art
Conducting visitor assessment studies
Refining, expanding, and standardizing use of microfadeometry in investigating light damage and refining use of microfadometry in risk assessment strategy
Examining protective effects of anoxic enclosures
Conducting accelerated aging experiments and theoretical modeling to better understand photochemistry of museum colorants under incandescent and solid state lighting
Examining and quantifying change in surface appearance attributes
Developing guidelines for selecting solid-state lighting
Developing case studies for museum lighting
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, carrying the potential for numerous and varied surface and bulk materials interactions. All these interactions involve some element 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, on some occasions, 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 and to understand it better in complex object stratigraphies could improve overall management and reduce the magnitude of these compromises.
At the simplest level, there are three components that mediate the interaction of light and artifacts: 1) the light source spectrum itself, (including filtration, intensity, and duration of exposure) 2) the current chemical states of materials used in artifact construction 3) the gaseous envelope that encompasses the artifact.
Without touching artifacts or altering their chemistry, the Museum Lighting Project's research sought 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;
assist museums world-wide adapting to the emerging technologies of solid-state lighting (LED) and provide a clearinghouse for information.
Page updated: July 2019