the paper substrate with an aqueous solution of the base and then wet the substrate with a solution of the epoxide for a time sufficient to allow the reaction to go to completion preferably the paper pre wetted with basic solution is allowed to dry before wetting with the epoxide solution drying the pre wetted paper may be accelerated by heating to a temperature in the range of from about 40 u00b0 c to about 75 u00b0 c the preferred epoxy is hexadecyloxirane i e the compound of the above formula wherein n is 15 the epoxide is preferably dissolved in an organic solvent for reaction with the cellulosic fibers any suitable organic solvent for the epoxide may be employed which is inert with respect to the cellulosic fiber containing material suitable such solvents include dimethylformamide sulfolane etc the preferred solvent is dimethylformamide dmf generally the solution should contain from about 4 to about 15 preferably from about 5 to about 10 weight volume of epoxide in order to enable the reaction with the cellulose fibers to proceed efficiently the reaction between the cellulosic fibers and the epoxide sizing agent is generally completed in from about 0 5 to about 2 min when.