238 REPORT— 1894. 



272,6 Action of Light upon Dyed Colours. — Report of the Committee, 

 consisting of Professor T. E. Thorpe (Chairmcm), Professor J. J. 

 Hummel {Secretary), Dr. W. H. Perkin, Professor W. J. Russell, 

 Captain W. DE W. Abney, Professor W. Stroud, and Professor 

 R. Meldola. (Brawn up by the Secretary.) 



During the past year the work of this Committee has been continued, 

 and a large number of wool and silk patterns, dyed with various natural 

 and artificial orange and yellow colouring matters, have been examined 

 with respect to their power of resisting the fading action of light. 



The general method of preparing the dyed patterns, and the manner 

 of exposing them under glass, with free access of air and moisture, were 

 the same as already adopted. 



The patterns were exposed at Adel, near Leeds, in the grounds of 

 James A. Hirst, Esq., to whom the best thanks of the Committee are 

 again due for his kind permission to do so. 



Each dyed pattern was divided into six pieces, one of which was 

 protected from the action of light, while the others were exposed for 

 different periods of time. These ' periods of exposure ' were made equivalent 

 to those adopted last year, by exposing, along with the patterns, special 

 series of ' standards,' dyed with the same colouring matters as were then 

 selected for this purpose. The standards were allowed to fade to the 

 same extent as those which marked off the ' fading period ' of last year, 

 before being renewed or removing a set of dyed patterns from the action 

 of light. The patterns exposed during the past year are therefoi-e 

 comparable, in respect of the amount of fading which they have ex- 

 perienced, with the red dyes already reported upon. 



The patterns were all put out for exposure on June S, 1893, certain 

 sets being subsequently removed on the following dates : — July 1, July 31, 

 August 26, 1893 ; February 19, June 12, 1894. Of the five 'periods of 

 exposure' thus marked oflT, periods 1, 2, 3 were equivalent to each other 

 in fading power, whereas periods 4 and 5 were each equivalent to four of 

 the first period in this respect ; hence five patterns of each colour have 

 been submitted respectively to an amount of fading equal to 1, 2, 3, 7, 

 and 11 times that of the first 'fading period' selected — viz. June 8 to 

 July 1, 1893. 



The dyed and faded patterns have again been entered in pattern-card 

 books in such a manner that they can be readily comjiared with each other. 



The following tables give the general result of the exposure experi- 

 ments made during the year 1893-94, the colours being divided, according 

 to their behaviour towards light, into the following five classes : very 

 fugitive, fugitive, modei-ately fast, fast, very fast. 



The initial numbers refer to the order of the patterns in the pattern- 

 books. The S. and J. numbers refer to Schultz and Julius's 'Tabel- 

 larische Uebersicht der kiinstlichen organischen FarbstoflTen.' 



The colours marked thus (*) appear to be somewhat faster than the 

 rest of the class in which they are placed. 



In the case of colouring matters requii'ing mordants, the particular 

 mordant employed is indicated in brackets after the name of the dye- 

 stuff". 



