artifacts to fulfill their visual purpose means there is an allowance of some physical risk. Even with this flexibility, light interaction should be limited to moments when an object is on view or undergoing study, and the level of lighting should be chosen accordingly. According to Museum Registration Methods, 5th edition, the suggested light levels for certain types of objects is as follows: "The traditional recommended light level for sensitive materials—including textiles, botanical and zoological specimens, pigmented objects, works on paper, and organic materials such as feathers, furs, and skins—is no more than 50 lux or 5 fc. Moderately sensitive materials, such as oils and acrylics on board and composite inorganic objects, should be exposed to light levels of not more than 150 lux or 15 fc. The traditional levels recommended for the least light-sensitive materials, such as stone, ceramics, metals, and glass, are not more than 300 lux or 30fc." Because lighting effects are cumulative, any limit in exposure – whether in time or in intensity – prevents material degradation. A period of intense or lengthy light exposure should be balanced out with periods of low exposure. Preventing light damage is difficult because light is necessary for visitors as well as people who are working with the objects. Exposure can be diminished by ensuring lights are only on when people are present, either by vigilant staff members turning on and off lights, timer switches or with motion sensors. Natural light from windows should be reduced or eliminated in all spaces by covering them with curtains, shades or UV absorbing filters. Where lights are on frequently, such as in galleries and office areas, a light meter should be used at least once a year to determine how much light objects are being exposed to, and adjustments should be made accordingly. In order to reduce the amount of light to which objects are exposed, several steps can be taken. Limiting the amount of time sensitive objects are put on display will help increase their lifespan. Schedules for displaying and resting objects should be developed in consultation with a professional conservator. Light levels for light sensitive objects such as textiles, works on paper, and dyed leather should be kept at 50 lux or less, and at a maximum of 200 lux for more light resistant materials, such as oil paintings, bone, and natural leather. Some material types, such as stone, metal, and