Blue Scales

This test strip can be used to determine the effect of light on paintings, documents and textiles.

The blue scale consists of 8 textile strips dyed with blue dyes of different degrees of fastness, the following strip each being approximately two times more lightfast than the preceding one. For use, cover half of the card is covered with aluminium foil and compare the color change after the exposure phase. The blue scale is a measure of the lightfastness of organic materials and an easy tool for convincing museum directors or exhibition makers.

Dimensions of the cards: 13 x 4.5 cm
Dimensions box with the textile strips 8 x 4.5 cm

Unfortunately there is no exact correlation between fading of the strips and a given dose of light in Mlx/h. Many materials exposed in museums are more vulnerable to light than the least lightfast strip of the card. No visible fading on the blue scale won't mean that no fading has occured on the exposed objecs.
For museums in fact we would need a more sensitive card but at the moment there is no such card available.
A color spectrometer can be used to document color changes on any kind of surface.
Monitoring the light dose during an exhibition can be done with a lux data logger.