M and tester Memoirs, Vol Ix. (191 6), No. 9. 7 



(b) More regular bleaching of the individual dyes. 

 (Y) Quicker printing. 



(d) Reduction of the heat developed in the Auto- 



chrome plate by the long exposures. 



(e) Greater saturation of the colours. 



(jT) Better fixation of the dyes remaining after 

 printing. 



The reproduction of the aolour screen image could be 

 got rid of by the introduction of a thin celluloid film 

 between the Autochrome plate and the sensitive paper. 

 This precaution was not even necessary in printing in 

 diffused light, as there was sufficient diffusion in the sen- 

 sitive film in this case, but the exposure was of course 

 greatly prolonged. 



The equalising of the bleaching action of the indi- 

 vidual dyes gave most trouble. Although we have to-day 

 a few thousand different aniline dyes, they are for the 

 most part too stable to light to be employed even with 

 the aid of a strong sensitiser for the bleach-out process. 

 Amongst those which might be sufficiently fugitive, many 

 are excluded on account of their bleaching, not to a white, 

 but to another shade, giving a dirty appearance to the 

 print. Others are debarred from employment on account 

 of the colour of the dye being recuperated when the print 

 is left in the dark ; others could not be used for want of 

 suitable companions of the correct shade of colour Or 

 speed of bleaching ; while others again bleach in such an 

 erratic way as to preclude their employment. 



I have examined many hundreds of dyes with regard 

 to their bleaching qualities, and I think I am safe in 

 asserting that no three are to be found which fulfil in a 

 thoroughly satisfactory manner all the varying demands 

 which are placed upon them, viz. : — 



