Exploring
Environmental Control
Temperature and Relative Humidity | Guidelines for Temperature and RH | Pollutants | Guidelines for Pollutant Levels | Light | Guidelines for Light Levels
Guidelines for Light Levels
Visible light is generally measured in lux (indicating the amount of light received by a surface). UV light is measured in microwatts per lumen. Guidelines for UV light are straightforward; light sources should emit less than 75 microwatts/lumen of UV. Protecting collections from visible light is more problematic.
Sunlight streaming in through a window exposes collections to damaging visible and ultraviolet light.
Certainly the most protection is provided by reducing light exposure completely (through storage in boxes or other enclosures). Light levels of 200 to 600 lux are required for comfortable vision in study and inspection areas; but storage areas can and should be as low as 10 to 50 lux. Lights should be turned off whenever possible. Ideally sunlight and daylight should be excluded completely from storage and use areas, or shades, drapes, and/or blinds should be used to reduce exposure as much as possible.
Due to the diversity of materials and their responses to light exposure, there is no standard for light levels during exhibition and use, but in general exhibition lighting for very light sensitive materials (this includes most paper-based items) should be limited to 50 lux, and exhibition time should be limited. Further information on exhibition can be found in Session 5: Collections Care.
