CHAPTER XIII 



FIXING, WASHING, AND DRYING 



By Beverly Dudley 



In general, the processing of photographic materials subsequent to that of develop- 

 ment includes: (1) rinsing the negatives in a short-stop bath to stop development and 

 to make the materials acid in order to prevent alkalinization of the fixing bath; (2) 

 fixing the material so that the developed latent image may be permanent; (3) washing 

 the material to rid it of the fixing solution which, in time, would otherwise stain it; 

 and (4) drying. Sometimes one or more of these processes may be omitted. For 

 example, short-stop baths are frequently dispensed with bj'- the amateur who processes 

 a relatively small quantity of material, and where the element of time is of importance, 

 as it is in newspaper work, negatives may be used while they are still wet. But the 

 normal procedure follows the processes enumerated above, and these will be dealt with 

 in this chapter. 



Short-stop Baths. Function of the Short-stop Bath. — The short-stop bath has two 

 important functions. Its main purpose is to arrest development of the latent image 

 after the photographic material is removed from the developer. If some short-stop 

 bath is not employed, the film of developer solution adhering to the negative or print 

 continues to develop the latent image much the same as if the photographic material 

 were permitted to remain in the developing solution. The second purpose of the 

 short-stop bath is to prevent the photographic material from carrying alkaline solu- 

 tions from the developer into the fixing bath where an excess of alkali renders the fixing 

 solution useless. The alkaline solutions which adhere to the film from the developer 

 may be partially removed by washing the film thoroughlj^ in water before fixing, but 

 removal of the alkali is made much more effective by placing the photographic material 

 in a short-stop bath or acid solution before fixing. The use of short-stop baths aids 

 in the prevention of fog and developer stains and helps to prevent sludging of the fixing 

 bath. If the acid short-stop bath contains hardening ingredients, it is possible to 

 eliminate the hardening agents in the fixing bath. 



Desirable Properties of Short-stop Baths.— The desirable properties of short-stop 

 baths have been summarized by Crabtree and RusselP in the following manner: 



1. The bath must be distinctly acid and to be efficient must remain acid during the 

 life of the fixing bath. Although the stop bath must be sufficiently acid to insure long 

 life, when the film leaves the bath, it is more or less acid and will therefore increase the 

 free-acid content of the fixing bath which in turn will increase the tendency of the 

 latter to sulphurize. The choice of acids therefore depends upon the propensity of 

 the acid to precipitate sulphur in a hypo solution. 



2. A stop bath should not be sufficiently acid to cause blisters, and the limit of 

 acidity in this case is much less than in the case of a fixing bath because the alkalinity 

 of the film is much greater when removed from the developer than after a slight rinse 

 and previous to the immersion in the fixing bath. 



1 Cbabtbee, J. I., and H. D. Russell, Some Properties of Chrome Alum Stop Baths and Fixing 

 Baths, J. Soc. Motion Picture Engrs., 14 (No. 5), 483-512 (1930). 



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