GB1309674A - Silver halide developer and process - Google Patents

Abstract

1309674 Photographic silver halide developer containing a 3-pyrazolidone H & W CO Inc 6 May 1970 [30 July 1969] 21910/70 Heading G2C A silver halide developer comprises an aqueous alkaline solution of a 3-pyrazolidone, a preservative for inhibiting oxidation of the 3-pyrazolidone and another developing agent which provides a super-additive developing effect with the 3-pyrazolidone, the 3-pyrazolidone being present in a molar ratio corresponding to 0À0096-0À5g of 1-phenyl-3-pyrazolidone per 240 ml of solution and being present in an amount such that it is responsible for more of the development than the other developing agent. The preservative may be sodium sulphite. A fixed (i.e. the amount of alkali available is unbuffered) alkali may be present as an activator for the 3-pyrazolidone e.g. a combination in solution of paraformaldehyde and sodium sulphite. Alternatively a buffered alkali may be used e.g. buffered sodium carbonate. The superadditive developing agent may be hydroquinone. The pH of the solution may be 8-12. The 3-pyrazolidone may be 1-phenyl-3 pyrazolidone. This developer may be used to produce continuous printing tones on an imagewise exposed high contrast, thin emulsion film by developing with a solution as defined above for 2-128 minutes at 18‹-27‹C. and fixing. The invention also comprises a concentrated aqueous alkaline solution of the developer defined above.