In making formula 2, the rosin and oleic acid are first dissolved in the solvent. Zein is slurred in the water with stirring; ammonia is added to the slurry, followed by the cool solvent-oleic acidrosin solution. Stirring is continued until the solution is complete. The most satisfactory solvents are n-butyl alcohol, ethylene glycol monobutyl ether, or methyl isobutyl ketone.