Limiting Light Damage From Display/Exhibition
Why should you care about light damage?
Light causes permanent and irreversible damage that affects the chemical composition, physical structure, and, what is usually most obvious, the appearance of the collection item.
Common examples of damage from ambient (that is, normal, everday) light include: faded ink inscriptions, yellowed newspaper clippings, now-magenta chromogenic (color) photographs, dark and brittle paper edges of books. Besides these examples, light damage can manifest as other undesirable changes, visible and not visible.
There are no conservation treatments that can undo light damage. Even if some visible manifestations of light damage can be lessened, the chemical and physical damage to the material will remain forever.
Which things are most sensitive to light? (and display recommendations)
Note: Light damage is cumulative and also depends on intensity and duration of exposure. In other words, dim light over a long period of time is just as damaging as bright light over a short period of time.
Extremely light sensitive -- Do not display; strictly limit use; invest in a reproduction
- certain kinds of photographs: salted paper prints, calotypes/talbotypes
- dyes (found in colored drawing media, inks, textiles, photographs, many early chemical reproductive processes such as blueprints, dittos)
Very light sensitive -- Avoid display and limit use if possible; strictly control light levels (max 3 footcandles and only when being viewed) and duration (max 3 months) of display; monitor object while on display
- poor quality paper (e.g., newsprint, many books printed in the U.S. between 1860-1990)
- dyed organic materials (e.g., dyed leather, wool tapestries)
- drawings and documents with ball point or felt tip pen ink, iron gall ink, colored pencils
- most photographs, including negatives, prints, slides, and direct positives
- textiles (e.g., upholstery, carpets, curtains, needlepoint)
Moderately light sensitive -- Strictly control light levels and duration of display (recommended max footcandles and duration determined by item); monitor object while on display
- wooden objects
- oil paintings
- tempera paintings
- undyed organic materials
Minimally light sensitive -- Consider light levels and duration of display; monitor
- most ceramics
- most glass
- generally, inorganic materials
Other risks from display (and mitigation strategies)
Other risk factors to consider for an object on display include:
- type of light
- temperature of display environment
- relative humidity of display environment
- pollutants in display environment
Displayed items should be inside a secure exhibition case. The light source should produce only visible light, no ultraviolet or infrared radiation. Some lamps (light bulbs) produce more heat than others; choose a lamp that does not produce a lot of heat and the lamp should be located outside of the display case. Monitor the temperature and relative humidty inside the case to ensure case environment stays within recommended parameters (determined by the material type of object displayed). All construction and trimming materials used for and in the display case should be chemically inert.
Protection from Light Damage (Northeast Document Conservation Center)
The Manual of Museum Exhibitions, ed. Barry Lord and Gail Dexter Lord, Walnut Creek, CA: AltaMira Press, 2002.
Light (Philadelphia Museum of Art)