GB565551A - Improvements relating to photographic hardening baths and processes - Google Patents

Abstract

565,551. Photographic hardening baths: KODAK, Ltd. (Eastman Kodak Co., and Vittum, P. W.). May 7, 1943, No. 7272. [Class 98 (ii)] A colour-developed gelatine silver salt emulsion is hardened, before removal of the developed silver, with an aqueous sulphite-free bath containing a gelatine hardening agent, an organic acid, and a buffer compound, with or without a boron compound such as boric acid or borax. The hardening agent may be potassium or chrome alum, the organic acid acetic acid, and the buffer compound sodium or other acetate, a citrate, or a borate. The bath reduces the tendency for the production of stain on removalof the developed silver. An example of a hardening bath is given. Three-layer colour photographic material may have as the cyan coupler in'the red-sensitive layer o-acetaminophenol, and after exposure, colour development, and hardening, may be treated first with a ferricyanide solution and then with a hypo solution. The colour negative produced may be printed on to similar material. The material may be of the kinds specified in Specifications 524,154, 524,554, 524,555 and 541,589. The material may also be processed to a positive by reversal colour development, the hardening bath being applied after the colour development. The hardening bath may also be employed after the separate re-exposures and colour developments involved in the reversal processing of material as in Specification 507,841 in which the couplers are not incorporated in the emulsions. The absence of sulphite in the hardening bath is advantageous where one of the following couplers is used : sebacic acid di-(3-hydroxyanilide, sebacic acid di-(2-hydroxyanilide), 2- hydroxy - 4<1> - (3 - phenoxybenzamido) diphenyl, 1 - hydroxy - 2 - (N - y - phenyl - n - propyl: N - phenyl) - naphthamide, N - n - butyl - 2 - cyanacetylnaphthalene - 7 - sulphanilide, N - n - amyl - 2 - cyanacetylcoumarone- 5 - - (p - ter. - amylsulphanilide), and p - tert. - butylphenoxyethyl p - benzoylacetammobenzenesulphonate.