SCEEENS PLATES EXPOSURE 



207 



the gelatin, and pour this at once on the plate ; the disadvan- 

 tage of this method is that it sometimes happens on drying 

 that the screen will be found to have a certain amount of the 

 dry dye, which has separated out, on its surface, and it is conse- 

 quently less transparent than those made by the first -mentioned 



FIG. 64. Improvised Glass Cell for Screen. 



process. This may often be remedied by rinsing the screen 

 under the tap for a few moments and then allowing it to dry 

 again with the same precautions as before. 



If a collodion film is required, the dye must be dissolved 

 in absolute alcohol, and this added to perfectly transparent 

 enamel collodion. No ordinary collodion dissolved in alcohol 



