The zeta potential, ζ, for cotton linters and bleached sulphate pulp has been calculated from measurement of the streaming potential. The measurements were taken at the same electrolyte and pH conditions as the charge/pH isotherms of Part 1. A comparison is made of the surface potential calculated under the same conditions from the charge/pH isotherms, negative adsorption experiments, polyelectrolyte theory and streaming potential measurements. It is shown that the ζ potential is not a good relative measure of the surface charge and cannot be used for qualitative comparison between such similar materials as bleached sulphate pulp and cotton linters.