Horgan's half-tone and photomechanical processes .. . With a prop-erly intensified negative there is not much danger of over-exposure. When the exposed copper plate is removed from theframe it is laid in a tray of clean water to permit the glueunhardened by light to soften. This will require a minute ormore, when the plate is placed under the tap and a strong jetof water allowed to fall upon it, which washes away thesoftened enamel. There is in a good light, sufficient differ-ence between the brown shade of the light-hardened glueand the pink of the bared copper to tell when the image isdevelo
Horgan's half-tone and photomechanical processes .. . With a prop-erly intensified negative there is not much danger of over-exposure. When the exposed copper plate is removed from theframe it is laid in a tray of clean water to permit the glueunhardened by light to soften. This will require a minute ormore, when the plate is placed under the tap and a strong jetof water allowed to fall upon it, which washes away thesoftened enamel. There is in a good light, sufficient differ-ence between the brown shade of the light-hardened glueand the pink of the bared copper to tell when the image isdeveloped clean. The best operators do not dye the enamelto determine when the development is finished. Should a dye be considered necessary, methyl violet is theone most commonly used. A weak solution of it is poured onand off the developed image, which it quickly stains. Thewriter has found an anilin dye called cotton blue to give abetter color contrast to the copper, and when enamel stainedwith it is flowed over with a weak solution of alum it changes. DUOGRAPH. Using half-tone and mezzograph & Manning, Philadelphia, Pa. THE HALF-TONE PROCESS 105 in color to a most brilliant blue. All anilin stains disappearas the enamel is being burned in. Overexposure, shown by slight traces of glue in theshadow dots, can be overcome by pouring on these dotsslightly warmed water, and spots requiring further develop-ment can be tickled clear by drawing over them wetcotton. Development being completed, the enamel is dried,in sunlight when possible. BURNING THE ENAMEL. Or, the copper plate is gripped with a wide-nosed pliersand moved over a proper gas stove until the moisture isslowly evaporated out of the enamel image; then the heat isincreased and the changing colors of the enamel watched sothat by moving the plate it will be heated alike over its wholesurface. As the heat of the copper increases the color of theenamel changes from a yellow to a brown, gradually becom-ing darker u
Size: 1241px × 2013px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, bookidhorganshalft, bookyear1913
