Paper sizing compositions and methods

A paper sizing composition comprised of at least one sizing agent selected from the group consisting of ASA, AKD and rosin wherein the at least one sizing agent is emulsified in water, at least one emulsion stabilizer, and from about 0.01% to about 15% by weight of at least one hydrophobic substance, based on the total weight of sizing agent present, wherein the sizing promotion efficiency of the paper sizing composition as determined by at least one method selected from the group consisting of the Cytec size testing method, the Hercules size testing method, and the Cobb size testing method is greater than or equal to about 4, and wherein the hydrophobic substance is selected from the group consisting of fatty acid esters comprising aliphatic fatty acid portions containing from about 7 to about 41 carbon atoms, which are optionally monounsaturated or diunsaturated and, whether unsaturated or not, are optionally substituted with at least one hydroxy group, triglycerides comprising aliphatic fatty acid portions containing from about 4 to about 22 carbon atoms, which are optionally monounsaturated or diunsaturated and, whether unsaturated or not, are optionally substituted with at least one hydroxy group, substantially straight chain hydrocarbons containing from about 6 to about 34 carbon atoms, which are optionally terminally unsaturated and, if unsaturated, are optionally isomerized, ASA derivatives formed from the reaction products of about 1 mole of ASA with about 1 mole of 1-octadecanol or 1-hexadecylamine, about 0.2 moles cholesterol or about 1 mole cholesterol, and the reaction products of about 9.25 or of about 3 moles ASA with about 1 mole castor oil, poly(dimethylsiloxane) optionally comprising side chains selected from PEO, PPO, and mixtures thereof, poly(diphenylsiloxane), poly(methylphenylsiloxane), poly(t-butyl-methylsiloxane), poly(dimethylsiloxane-co-alkylmethylsiloxane) where the alkyl comprises, independently, from about 1 to about 18 carbon atoms, poly[dimethylsiloxane-co-3-(aminopropylmethylsiloxane)], hydride-terminated poly(dimethylsiloxane), distearate-terminated poly(dimethylsiloxane), aloe-emodin, aloin, cholesterol, lanosterol, and mixtures thereof, with the proviso that the hydrophobic substance is not highly alkoxylated.