File:The American annual of photography (1922) (14758717236).jpg

Identifier: americanannualof36newy (find matches)
Title: The American annual of photography
Year: 1922 (1920s)
Authors:
Subjects: Photography
Publisher: New York : Tennant and Ward
Contributing Library: Harold B. Lee Library
Digitizing Sponsor: Brigham Young University

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y,two volumes of water, in order to secure the same contrastthe negatives should be developed for three times as long. Thefog values for equal contrasts are likewise approximately equal. A dilute developer, however, oxidizes more rapidly than onewhich is more concentrated, the rate of oxidation being roughlyproportional to the sulphite concentration. Sodium sulphite atstrengths higher than 10% to 15% oxidizes more or lessslowly, but very rapidly at strengths below this. This is veryapparent with developers intended for use with a reel and tankoutfit. If the developer contains 10% to 15% of sodiumsulphite, very little fog forms on churning up the developer,but if the developer is diluted with only 50% of water, fogmay begin to form very rapidly.* With Elon-hydroquinone the time of development is roughlyinversely proportional to the dilution up to a dilution of one tothree, though there is a tendency for the weak developer to give «See Article Chemical Fog CAmer. Ann. 1919, p. 20). 204
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<o QWPi< 205 more fog than the stronger developer when developing to agiven contrast. Beyond a certain dilution prolonged develop-ment does not increase contrast, because fog grows at a greaterrate than the image. A glycin developer will withstand more dilution than anyother known developer and still behave rationally, and for thisreason glycin has long been a favorite developer for tankwork. (b). Effect of Temperature. With developers such as hydro-quinone, development proceeds very slowly at low tempera-tures, so that a developer of this type, as compared with anElon-hydroquinone developer tested under arctic conditionswould prove very unsatisfactory. For tropical work, a de-veloper is required which will not cause undue swelling of thegelatine or excessive fog. (c). Alkalinity. A developer which is strongly alkalineshortens the life of the acid fixing bath because the acid in thelatter is rapidly neutralized by the alkali in the developer car-ried over by the films and prints

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