3. Exposure to artificial light

3.1 General considerations

Because of the difficulties of repeatability and reproducibility encountered in natural light exposure tests, there has long been an attempt to replace natural light with artificial light sources that are theoretically much more constant than sunlight. The difficulty lies in choosing a source whose radiation is as close as possible to sunlight, or whose effects are identical to those caused by sunlight. The use of an artificial light source can also accelerate the ageing process by increasing power.

The most widely used light source today is the xenon arc lamp. Its essential characteristic, when suitably filtered, is to have a spectrum fairly close to that of sunlight.

An exposure method using fluorescent lamps...