528 HANDBOOK OF PHOTOGRAPHY 



Purple Spots. 



1. Distinguishing Characteristic. — Purple spots on negative. 



2. Cause. — Dry particles of the developer settling on negative. 



3. Prevention. — Keep negative protected from chemicals. Do not mix chemicals 

 in same room in which processing is being done. 



4. Remedy. — See remedy for Brown Spots, page 524, for remedy which is useful in 

 some instances. 



Rack Marks. 



1. Distinguishing Characteristic. — Single or double line markings which may 

 sometimes be mottled; marks uniformly spaced. 



2. Cause. — Dr^'ing roll film on wooden or metal racks. The marks are produced 

 where the rack touched the film and prevented free circulation of solutions. Most 

 frequent in motion-picture processing. 



3. Prevention. — In motion-picture processing, continuous machine rather than 

 rack processing will prevent these marks. If rack processing is used, some means of 

 shifting or rolling the film on the racks so that the same portion of film is not always 

 adjacent to the racks during processing will help prevent rack marks. 



4. Remedy. — None. 



Small Circular Spots. 



1. Distinguishing Characteristic. — Small, circular, light or transparent spots. 



2. Cause. — Air in water used for making or diluting developer, or excessive 

 agitation during development. 



3. Prevention. — Use of distilled or boiled water free from air. If this is not 

 possible, let water stand for at least an hour before using it to make up solutions. 

 If due to excessive agitation, less vigorous agitation is required. 



4. Remedy. — Possibly local intensification. 



Small Circular Spots with Shaded Edges. 



1. Distinguishing Characteristic. — Small, circular, transparent spots with shaded 

 edges. 



2. Cause. — Air bells or bubbles forming on negative during development. 



3. Prevention. — Removing of air bells bj^ wetting the negative completelj' prior 

 to development. Agitate negative in developer to prevent formation of bubbles, or 

 brush over the surface with soft camel's-hair brush. Agitate developer. 



4. Remedy. — None. 



Spots of Irregular Shape. 



1. Distinguishing Characteristic. — Light or transparent spots of irregular shape, 

 usually distributed along one side of negative and less frequentlj' over entire negative. 



2. Cause. — Exhausted or improperly compounded developer. 



3. Prevention. — Use of fresh or correctly compounded developer. 



4. Remedy. — Retouching. 



Transparent Spots. 



1. Distinguishing Characteristic. — Light or transparent spots indicating a deficiency 

 of silver deposit. 



2. Cause. — Such spots may be caused by: (o) dust or dirt on film during exposure 

 or development; (6) air bells (q.v.); (c) air in water making up developing solution ; 



