Preventive Conservation: Harmful Light Levels
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A Chinese court robe that has faded from long years of exposure to high light levels on exhibit. Because it was folded, the robe has faded unevenly; part of the sleeve on the right was protected from exposure and maintains the silk’s original bright color.

 

Light is a form of energy that can cause severe damage to specimens and objects. Exposure to both the visible and the invisible, or ultraviolet, portions of light will cause damage. Organic materials are most susceptible to light, but dyes, paints and other inorganic materials can also be affected. Damage from light is cumulative and irreversible.

This Great Lakes Indian buckskin shirt was exhibited on a mannequin for many years. The dark band in the leather where it was protected from light by the strap of a bandolier bag shows how badly the rest of the leather has faded.

The most familiar form of damage is fading, a condition with which most people are familiar. Energy from light causes chemical reactions to occur on the surface of the specimen that result in the loss of color.

Silk neckband of a Chinese court robe. The silk fibers, exposed to extremely high light levels for many years, have become brittle and the fabric is ripping and disintegrating.

Light can also cause structural damage in specimens and objects by breaking down constituents. The structural weakening, often signaled by discoloration, leads to embrittlement and disintegration.

For all these reasons, light levels are kept low and windows are blocked in exhibition halls to protect specimens and objects on display.