A method of stabilizing an aqueous solution of polyaminoamide-epichlorohydrin resin comprising adjusting the pH of the solution to less than about 3 with strong acid and then adding to the solution a weak acid in a mole ratio of total protons available from the weak acid to total protons available from the strong acid of about 0. The cot includes a sheet of fabric and a pillow. Gas is introduced into the milling container above the package of grinding bodies.