Manchester Memoirs, Vol. Ix. (191 6), No. 0. 5 



The results obtained at that time were crude ; the 

 colours were not rendered harmoniously and the exposures 

 were very long. Still some very fair reproductions of 

 brilliantly coloured window transparencies were obtained. 



These workers were soon followed by Szczepanik and 

 by myself. Szczepanik (9) patented a process by which 

 the separate dyes were embedded in different layers with 

 a view to preventing the dyes from reacting injuriously 

 on each other. He used practically the same materials 

 as Neuhauss and Worel, but his results were not much 

 better in spite of his much more complicated method of 

 working. His paper was, however, the first obtained by 

 coating a paper support directly with dyed emulsions. 



In 1904, after prolonged research, I placed a bleach- 

 out paper on the market, the first of its kind. I had 

 naturally profited by the work of my predecessors, but 

 there were several noteworthy improvements in this first 

 commercial paper, introduced by my then co-worker Dr. 

 Merckens and myself. The dyes employed were to some 

 extent new and prepared by ourselves, and we were able 

 to bring all the dyes into one emulsion layer zip on paper. 



Szczepanik (10) employed alternate layers of collodion 

 and gelatine for coating his dyes upon paper, while we 

 were able to obtain our dyes in a single layer of collodion. 

 To prevent the emulsion from penetrating into the body 

 of the paper we had a thin insulating film of gelatine 

 coated on the paper first. Anethol was used as a sensi- 

 tiser. 



We studied the action of various dyes upon gelatine 

 and collodion, and found (11) that the basic dyes had 

 generally strong affinity for the collodion, while the acid 

 dyes showed more affinity for gelatine. The affinity of 

 the dyes is sometimes so great that they will not only 

 leave a medium of lesser affinity for one of greater affinity 



