370 



HANDBOOK OF PHOTOGRAPHY 



Commercial Development of Roll Films and Film Packs. — Under the conditions 

 generally obtained in the commercial handling of amateur roll films, little individual 

 attention can be given, particularly as the range of exposures on any one film is 

 often so great that no one compensation of development could possibly be beneficial 

 to all the pictures. Accordingly, there is a considerable tendency to use developer 

 and development that will produce a good average out of the entire range of exposures. 

 For very obvious commercial reasons, the development time should be moderate, as 

 too short times would lead to difficulties in the control necessary for uniform quality, 

 and prolonged development reduces the output. A long useful life is also necessary 

 for satisfactory commercial work. A typical formula is : 



No. 17 Roll Film Developer 



Rhodol (metol or Elon) . 75 g. 44 gr. 



Sodium sulphite (anhydrous) 9 . 00 g. 1 oz. 87 gr. 



Sodium bisulphite 9 . 00 g. 1 oz. 87 gr. 



Hydroquinone 3 . 00 g. ] 75 gr. 



Pyro 0.75 g. 44 gr 



Sodium carbonate (monohydrated) 22. 5 g. 3 oz. 



Water to 1 1. 1 gal. 



With this formula, No. 17, normal development will take 7 to 14 min. at 65°F., 

 depending upon the contrast desired and the films developed. The formula may be 

 made somewhat more active by increasing the concentration of reducers. 



Developers for Papers. — In choosing a developer for a printing paper, contrast and 

 life characteristics are important, but attention must also be paid to the general tone 

 of the final image. This tone can often be varied from cold tones, blacks and blue- 

 blacks, to warm tones, brown-blacks, by choice of developer formula. The same 

 formula frequently gives different tone quality on different papers. Hence no general 

 rules for selection of developer formula can be laid down here. In general any factor 

 which affects the grain-size distribution in the developed image will have an effect on 

 its tone. Sometimes the addition of special compounds is suggested to give partic- 

 ular tone characteristics. These are presumably effective through an effect on the 

 state of division of the silver particles making up the image. 



The formulas recommended for different papers vary rather widely both in ratios 

 of original constituents and in dilution. Most commonly they are metol, hj'dro- 

 quinone, carbonate developers. In many cases they are originally mixed as concen- 

 trated stock solutions, then diluted and used as needed. 



Table VII. — Developers for Printing Papers 



Rhodol (metol or Elon) 



Sodium sulphite (anhydrous) 



Hydroquinone 



Sodium carbonate 



I'otassium bromide 



Water to make 



No. 18 



Metric 



g. 



1.2 

 19.0 g 



4.0 g. 

 26.0 g 



0.40 g 

 1 1. 



Avoirdupois 



70 gr. 



2 oz. 232 gr. 

 232 gr. 



3 oz. 200 gr. 

 23 gr. 



1 gal. 



Range 



Metric 



0.6- 1 . 5 g. 

 7 . 5-22 . 5 g. 

 2.0- 6 . g. 

 7.5-30.0 g. 

 0.3- 1.5 g. 

 1 1. 



Avoirdupois 



35- 87 gr. 



1- 3 oz. 



115-350 gr 



1- 4 oz. 



17- 87 gr. 

 1 gal. 



It is strongly recommended that papers be developed in the formulas suggested 

 by the manufacturers, as good print tone and contrast depend upon the use of a for- 

 mula suited to the paper. 



