Invert size for the internal and surface sizing of paper

In an invert size for the engine and tub sizing of paper, comprising an aqueous dispersion of a fortified, hydrogenated or disproportionated and optionally esterified rosin or mixture of such rosins and of a dispersant that contains digested casein or an emulsifier of the formula

• [R--(OCH.sub.2 CH.sub.2).sub.n --O--A].sup.-.sub.x M.sup.x+(I)
• wherein R is an alkylphenyl, alkyl, or alkenyl group or a cycloalkyl group with condensed rings, A is a group of the formula --CH.sub.2 COO or --SO.sub.3, M.sup.x+ is a cation, x is 1 or 2, and n is a number such that approximately 21 to 76% of the molecular weight of the anion is in the --OCH.sub.2 CH.sub.2 groups, the improvement which comprises including cationic starch in the dispersion as a dispersant, the dispersion by weight comprising about 5 to 50% of the rosin or mixture of rosins and 1 to 15% of the dispersant based on the rosin or mixture of rosins, with the remainder consisting essentially of water, the ratio of the weight of casein or emulsifier of Formula I to the weight of cationic starch in the dispersant ranging from about 20:80 to 80:20, the ratio of the weight of rosin:
• cationic starch ranging from about 1:0.0280 to 1:0.0710.