This part of ISO 105 specifies a method intended for detecting and assessing Change in colour, after brief exposure to light, of coloured textiles which Change in colour on exposure to light but which virtually return to their original shade when stored in the dark. NOTE 1 This phenomenon used to be termed “phototropism”, but the term “phototropism” is much more widely used in biological science where its meaning is entirely different. As the derivation of “phototropism” is in accord with its biological meaning, the term “photochromism” is preferable for reversible colour changes induced by light.