ORDINARY plates which are sensitive to the blue, violet and ultra-violet may be made sensitive to other colors by .the use of certain dyes. These may be incorporated in the emulsion, or the dry plates may be made sensitive by bathing in dilute solutions of the dyes.
This investigation was undertaken to study some of the conditions to be observed in the use of certain dyes for making ordinary plates color sensitive by bathing.
Pinaeyanol (a red sensitizer) gives good results in dilute alcoholic solutions when used with ammonia, but plates bathed in Water and stock solution keep much better and are almost as sensitive, provided they are thoroughly washed before sentitizing. This is because the soluble salts contained in the emulsion prevent the sensitizing action by flocculating the dye.
Wash or soak the plate in water for five minutes, and ba~,the for two minutes in the following bath at I 8 Β° C.
Water ............................ IOO parts Pinacyanol (stock solution I to IOOO).. 4 " Rinse the plate in ethyl alcohol for three or four minutes and dry as rapidly as possible. Stock solutions consist of I part (lye to Iooo parts ethyl alcohol. Films are best sensitized in a bath containing water, alcohol, ammonia and stock solution as follows. Bathe for four minutes in Water ............................ 65 parts Ethyl alcohol 95 per cent .............. 35 " Pinacyanol (stock solution I to IOOO).. 4 " Ammonia 28 per cent ................ 2 " Rinse in alcohol for three or four minutes and dry rapidly.