Fading of the British Dyed‐wool Light‐fastness Standards in the U.K.: Some Energy Measurements

The relation between the fading of the British dyed‐wool light‐fastness standards in the U.K. and the amount of solar radiation required to produce the fading has been investigated. It has been shown that the successive standards require exposures to quantities of solar radiation which increase, in general, by a factor of two, but there is a considerable range of energy values for any one standard, this range being great enough to permit some overlapping. It is suggested that this may be because the Eppley pyrhelio‐meter records all radiant solar energy, whereas only a fraction, which may be variable, is operative in the fading of the standards.