Hardening photographic layers containing silver halide with a 1-sulphonyl-4-amino-pyridinium salt

A process for providing a photographic material comprising at least one silver halide emulsion associated with at least one supported layer containing protein as a binder in which the protein-containing layer is contacted with an effective amount of hardener to harden the layer

• wherein the improvement comprises the hardener is a 1-sulphonyl-4-amino-pyridinium salt of the following general formulae:
• ##STR49## in which R.sub.1 represents alkyl with 1 to 4 carbon atoms, aryl optionally substituted by halogen, aralkyl, a sulphoalkyl or sulphoalkenyl group with 3 to 4 carbon atoms or a dialkylamino group in which the alkyl portion contains 1 to 3 carbon atoms,
• R.sub.2 represents hydrogen or alkyl,
• R.sub.3 has the same meaning as R.sub.2 or it represents an aminocarbonoyl group or together with R.sub.2 it represents the atoms required to complete a condensed benzene ring,
• R.sub.4 and R.sub.5 represent hydrogen or alkyl,
• R.sub.6 represents hydrogen, alkyl with 1 to 3 carbon atoms, aralkyl or sulphoalkyl,
• R.sub.7 represents hydrogen or alkyl with 1 to 3 carbon atoms or together with R.sub.6 and the nitrogen atom it represents the atoms required to complete a saturated heterocyclic 5-membered or 6-membered ring, and
• X.sup.- represents halogen .sup.+, R.sub.1 --SO.sub.3.sup.- or a hard anion from the group ClO.sub.4 ', BF.sub.4 ', PF.sub.6 ' or Sbf.sub.6 ', X.sup.- being absent if R.sub.1 or R.sub.6 contains a sulpho group.