AbstractThe extent of swelling of refined and unrefined cotton linter, viscose pulp and paper pulp treated with various concentrations of NaOH from 4 to 20% at 20°C, then washed with water and never dried was measured in terms of the water retention values (WRV). The treatment of unrefined fibers with alkali resulted in increase in WRV; the only exception was viscose pulp treated with 12 and 14% NaOH. Cotton pulp refined with 5% NaOH showed an increase in the swelling ability in water which increased with the concentration of alkali treatment, whereas for viscose and paper pulps the amount of water retained increased with alkali concentration up to 12% and 14% NaOH, respectively, then decreased with further increase in alkali concentration. For cotton and viscose pulps refined with 20% NaOH, the alkali treatment increased the affinity of fibers to water up to alkali concentrations of 16% and 12% NaOH, respectively,′ then the WRV became more or less stable after treatment with higher concentrations of NaOH. On the other hand, the paper pulp refined with 20% NaOH then treated with alkali concentrations from 10 to 20% showed decreased WRV.