The American annual of photography . de Sodium Sulphite (desiccated) A Sodium Carbonate (desiccated) B Water to 1000 cc. Effect of Varying the Sulphite Content While B was maintained constant and equal to 100 grams,A was varied as follows: (A) Time for Fog on Cine Positive at 80° F. 25 grams 3 mins. 50 3/2 75 5 100 6 125 7 150 6 Any increase in the sulphite content beyond 100 grams con-siderably retarded the rate of development, and as a minimumof fog was produced at this point, 100 grams was considered tobe the most suitable of Varying the Carbonate Content A was maintai
The American annual of photography . de Sodium Sulphite (desiccated) A Sodium Carbonate (desiccated) B Water to 1000 cc. Effect of Varying the Sulphite Content While B was maintained constant and equal to 100 grams,A was varied as follows: (A) Time for Fog on Cine Positive at 80° F. 25 grams 3 mins. 50 3/2 75 5 100 6 125 7 150 6 Any increase in the sulphite content beyond 100 grams con-siderably retarded the rate of development, and as a minimumof fog was produced at this point, 100 grams was considered tobe the most suitable of Varying the Carbonate Content A was maintained constant, equal to 100 grams, and Bvaried as follows: (B) Time for Fog on Cine Positive at 80° grams 3 mins. 50 3/2 75 4J4 100 S 125 5 ISO 4^ The least fog is therefore produced when the content ofboth carbonate and sulphite is equal to 100 grams. The most suitable formula is therefore: Elon grams Hydroquinone 10 Potassium Bromide Sodium Sulphite (desiccated) 100 Sodium Carbonate (desiccated) 100 Water to 1000 wo Q w 29 The effect of dilution of this formula was to increase fog asfollows: To lOO volumes of the, developer C volumes ofwater were added. (C) Time for F6g on Cine Positive at 80° vols 5 mins. 50 3 100 2 150 2y2 200 3 In practice on the large scale, the above developer was foundto give positives remarkably free from fog even after continualuse with the temperature of the developer and surrounding at-mosphere at 80° F. It was found that if the developer was splashed on the floorduring working, this crystallized out and caused trouble due toparticles of sulphite and carbonate dust settled on the was overcome by replacing the sodium carbonate by anequal weight of desiccated potassium carbonate, since owing tothe dehquescent nature of the latter, any liquid splashedaround did not dry up but remained moist. The developer con-taining potassium carbonate was also somewhat more ener-getic than the one containing sodium carbonate. The in
Size: 1196px × 2089px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, bookpublishernewyo, bookyear1919
