A process as described in claims 19, 20, or 21, wherein said mordant comprises polymer comprising vinyl repeat units having tertiary amino groups or quaternary ammonium groups and wherein said vinyl repeat units are selected from the group consisting of: ##STR12## wherein R1 is a hydrogen atom or a lower alkyl group having 1 to 6 carbon atoms; L represents a divalent linking group having 1 to 20 c