Abstract

In most works, selection of dyes for the dyeing of leather is based on long years of practical experience. Yet accelerating changes in fashion which involve changes in processing methods, particularly regarding retanning, fatliquoring, etc., as well as changes in countries of origin of skins, result in a change of behaviour of these leathers during dyeing. Frequently operational considerations prevent changes in substrate and in method of dyeing. Dyeing results can, however, be substantially improved by an optimum dye selection in accordance with recently established criteria. The dyeing behaviour of any dye on leather is influenced by many factors. It is difficult to create conditions that are exactly reproducible. Under the name of “Dermagen testing method” a process has been developed which is characterised by the mass-dyeing of a leather pulp made of shavings of a standard-tanned leather. Depending on the standard depth figures are established for build-up power, the saturation limit as well as the affinity of a dye. On the basis of the numbers of affinity and the build-up power clues can be won about the behaviour of dye or combinations of dyes on leathers of varying pretreatment. Thus the selection of dyes on the basis of their dyeing behaviour is greatly simplified.