143 



The Shrinkage of Photographic Paper. 



R. R. Ramsey. 



In mountiiijj; some spectrograph prints I was very much chagrined to 

 find that they were at different lengths, as if they had heen talcen on 

 different spectographs. These pi-ints had heen printed on developing paper, 

 developed, washed, dried and then soake<l and mounted ^xet. It had 

 happened that the paper used came in (piite large sheets and in cutting 

 down ro size it was economical to cut some pieces lengthwise of the paper, 

 ■while other pieces wen; cut crosswise. Several prints were made and 

 the l)est were selected for mounting. In tliis c-hance selection some were 

 lengthwise and others were crosswise of the paper. The expansion and 

 contraction in the process of develo]ung and washing was different in the 

 different directions <ind it was necessary to make a new set of prints, 

 care being taken to have tlie paper all cut the same way. The mounting 

 was done before drying, to prevent excessive exjiansion. 



I thought it might be of interest to experiment with several brands 

 of paper to determine if this fault was found in ail l)rands of paper or 

 in this particular brand alone. 



An SxlO-iiich plate was exj^osed to sunlight and then developed, giv- 

 ing a very dense tllm. On the edges millimeter scales were ruled with the 

 dividing engine. A space of 20 centimeters was ruled on the long edge 

 and a 15 centimeter space on the short edge of the plate. Thus by print- 

 ing and developing I had a photograph of the scale, and measurement 

 would give the amount of shrinkage or exitansion. Five different papers 

 were used. All were printed, developed, fixed, and washed in the usual 

 manner. After washing, a sample of each brand was mounted on card- 

 board. The otliers wei"e stuck back side to glass and allowed to dry. 

 When dried measurements were taken of the length and breadth. Then 

 'famples of each brand were selected from the unmounted photographs, 

 soalved in water and mounted on cardboard. After drying, these were 

 also measured. 



