the efficiency by which pulp cooking liquor components penetrate the wood and enable lignin and resins to be removed from the cellulosic materials is increased by contacting wood chips and the like with a liquid mixture comprised of white liquor containing at least one surfactant selected from the group consisting of a polymethylalkylsiloxane ; a co - and terpolymer of silicone and a polyhydric alcohol ; an alkoxylated aryl phosphate ; an alkoxylated branched alkyl phosphate ; an alkoxylated branched alcohol ; an alkyl polyglycoside , an alkoxylated alkyl polyglycoside ; a mixture of alkali metal salts of alkyl aromatic sulfate , a sulfosuccinate and a silicone ; and combinations thereof ; for a residence time effective to extract resinous components without substantial degradation of cellulose and thereafter heating at least a portion of the resulting mixture and wood chips .