320 OUR PHYSICAL WORLD 



the light areas of the object and transparent areas correspond- 

 ing to the dark areas of the object; it is therefore known as 

 the negative (Fig. 1620). When thoroughly dry, it is to be 

 used to make the print or picture (Fig. 1626). If one is 

 developing several plates, one after another, he should be sure 

 to wash off from his fingers all traces of the fixer before handling 

 the next plate, for the fixer readily spoils the developer. When 

 through developing, put the fixer into the large- stoppered bottle 

 to save for the next lot of plates. It will fix six dozen 4X5 

 plates. The developer is to be made up fresh for each new 

 batch of plates. One tube of developer is sufficient for a dozen 

 such plates. 



The roll of films is handled in the same manner except that 

 one holds an end of the roll in each hand and runs it through 

 first the water and then the developer (Fig. 163). It is not 

 necessary to wipe its surface with the cotton as the movement 

 takes off the air bubbles. If the exposures are not accurate 

 in the several films so that some images develop rapidly and 

 others slowly, it will be wise to wash off the developer in the 

 water when this fact is apparent, cut the roll into its separate 

 films, and develop each separately. When fixed, films are pinned 

 up to dry on a taut string like clothes on a line. 



Many photographers now prefer to use the tank method of 

 developing. A tank developer is then used, which can also be 

 purchased in tubes. The tank is filled with the developer at 

 proper temperature, the plates (or film) are put in and left for 

 the time specified on the directions, when the developer is poured 

 off and the fixer is added. 



To make a print, remove the back from a print frame and 

 lay the negative in, its uncovered side toward the light. A 

 film must be laid on a piece of clean glass that fits the print 

 frame. In the darkroom, take a sheet of print paper from its 

 box or envelope and lay it on the negative, film side of the paper 

 against that of the plate. The film side of the paper is told in 

 the same way as in the case of the plate, though the difference in 



