Abstract

A known technique to measure the water vapour permeability of leather is described by ISO 14268 and similar standards. These methods rely on the adsorption of the water vapour by a solid desiccant inside a closed vessel that is separated from a conditioned atmosphere by the leather piece. The mass increase of the desiccant corresponds to the amount of moisture transmitted by the specimen and is thus used to calculate its water vapour permeability. In this investigation different desiccants are used to measure the permeability of a chrome split and of cellulosic membranes, showing that the results are influenced by the features of the desiccant. As accounted by the theoretical model proposed, the outcome of the measurement is affected by a systematic error that leads to an underestimation of the true value of permeability.