143 



The Shrinkage of Photographic Paper. 



R. R. Ramsey. 



In mounting some spectrograph prints I was very much chagrined to 

 find that they were at different lengths, as if they liad heen taken on 

 different spec-tograiihs. These prints had been printed on developing paper, 

 developed, washed, dried and then soaked and mounted wet. It had 

 happened that the paper used came in quite large sheets and in cutting 

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

 while other pieces were cut crosswise. Several prints were made and 

 tlie best were selected for mounting. In this chance selection some were 

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

 contraction in the process of developing and wasJiing was different in the 

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

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

 was done before drying, to prevent excessive expansion. 



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

 of paper to determine if this fault was found in ail brands of paper or 

 in this particular brand alone. 



An SxlO-inch plate was exjiosed to sunlight and then developed, giv- 

 ing a very dense fllm. On the edges millimeter scales wore 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 shrinkai::(> or ex])ansion. Five different papers 

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

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

 board. The others were stucli back side to glass and allowed to dry. 

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

 samples of each brand were selected from the unmounted photographs, 

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

 also measured. 



