A simulator is described for rinsing processes carried out on open-width washing machines. In combination with a theoretical model, a simple method is given for testing rinsing processes. The method has been used to investigate the extraction of caustic soda from a cotton fabric, varying the temperature, fabric velocity and type of fabric. The results were verified by measurements in a commercial open-width washing machine. The absorption of carbon dioxide from the atmosphere in the washing waterisshown to beimportant forremoving the caustic soda. The method may be used in practical situations to optimise process conditions. mercerisation. The results were verified by experiments on a commercial scale.