File:The American annual of photography (1912) (14765966945).jpg

Identifier: americanannualof1912newy (find matches)
Title: The American annual of photography
Year: 1912 (1910s)
Authors:
Subjects: Photography
Publisher: New York : Tennant and Ward
Contributing Library: Harold B. Lee Library
Digitizing Sponsor: Brigham Young University

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0 oz. Gum Arabic i^ oz. Glycerine 3^ oz. or 10 lumps of ordinary white sugar dissolved in one quartof distilled water may serve as a substitute. The plates will be found to work perfectly clean and toretain their color sensitiveness, even if worked under themost unfavorable conditions. ETHYL VIOLET VERSUS PINACYANOL. The question has been raised whether the very delicatepinacyanol has proven the ideal red sensitizer for collodionemulsion. We feel inclined to answer in the negative. Pina-cyanol sensitized emulsions are liable to completely lose colorsensitiveness within a few days and serious disturbance tobusiness routine has been caused by this undesirable prop-erty. Ethyl violet sensitized emulsions will keep indefinitely,actually improving with age. The red sensitiveness of thelatter is, of course, not as great as that of the former anda deeper filter must be used. However, this increased ex-posure may be compensated for by larger lens apertureswhich pinacyanol does not permit. 284
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CHILD PORTRAIT. C. F. Townsend. Moreover ethyl violet 6B, or ethyl purple, as it is commonlycalled, is a very cheap dye, pinacyanol very expensive. Thereason why pinacyanol is unreliable we believe to have tracedto minute quantities of viugl-alcohol C2H4O2 present in thesolvents used in the preparation of collodion emulsion. Asimilar difficulty is met with when panchromatizing dry plateswith p^inachrome. The distilled water shows in most casesacid reaction and completely discolors the dye bath aftera few minutes. The addition of ammonia restores the color,but seriously impairs the keeping qualities of the plate. TEST FOR PURE SOLVENTS. Operators are often called upon to dissolve emulsion pel-licle and it will be necessary for them to test their alcoholand ether. The alcohol must be 95 per cent., specific gravity 0.790and stand the following test: Prepare a 10 per cent, agu solution of nitrate of silver, afew drops of which are added to the alcohol in the test tube.Now add ammonia in e

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