Photomicrography 



49 



Figs. 55, 56, 57, and 58. Processing 4- by 54n. sheet film in tanks. Fig. 55. The film 

 is inserted in a holder. Fig. 56. The film is lowered into a tank of developer. Fig. 57. 

 The film is removed from developer and lowered into a tank of hardener or "short- 

 stop." Notice that the developed silver image is clearly visible in contrast to the white 

 background of the undeveloped silver bromide. Fig. 58. After fixation the film is 

 removed to the washing tank. Notice that the image is no longer visible, because the 

 silver bromide has been dissolved out in the fixer. 



4. Transfer hangers to tank of acid fixer. Agitate 15 sec, leave 10 min. 

 Lights may be turned on after 2 min. 



5. Transfer hangers to tank of running water ( Fig. 58 ) . Leave 15 min. 



6. Dip hangers for 30 sec in diluted Photoflo or similar wetting agent 

 and hang up to dry. 



Processing Positive Materials. Processing papers is much less trouble 

 than films both because the times are shorter and because the operations 

 may be conducted in green light. The steps are just the same. Special 

 developers are made for papers and are almost without exception solu- 

 tions of p-diaminophenol and hydroquinone in a mixed solution of sodium 



