FACTORS AFFECTING ORANGE PEEL *

A bstract The effects of spraying techniques on orange‐peel surface of porcelain enamel were studied. The volume of atomizing air per unit volume of atomized slip is the predominating factor, and the ratio appears to be 1000 to 1200 cc. of air per 1.0 cc. of slip for average conditions. The angle of incidence should be 60 degrees or more. The minimum fluid and atomizing pressures should be adjusted to suit the specific gun nozzle and tip but should maintain the air‐to‐slip ratio indicated. The following conclusions are given: (1) The type of fluid nozzle of the spray gun alone does not appreciably affect orange peel; (2) the type of air cap and its air capacity affects orange peel definitely; the tip with the largest number of orifices and greatest air capacity offers much better atomization and smoother spray, and there is a definite indication that the fineness and degree of atomization is a measure of the amount of orange peel that may be expected; (3) lowering the atomizing pressure increases the tendency toward orange peel; (4) increasing the rate of flow of the enamel through the spray gun increases the tendency toward orange peel; (5) closer spraying distances increase the tendency toward orange peel; (6) decreasing the angle of incidence of the spray increases the tendency toward orange peel; (7) a round, concentrated spray has a greater tendency toward orange peel than the wide flat spray fan; (8) increasing the application weight increases the tendency toward orange peel although good results could be obtained up to 50 to 55 gm. per sq. ft. in one coat; (9) decreasing the specific gravity of the enamel slip increases the tendency toward orange peel; the best specific gravities for spraying cover‐coat enamels are above 1.80; and (10) the viscosity of the enamel slip does not appreciably affect the orange‐peel tendencies of the enamel, but there is a definite indication that the best results are obtained with the higher viscosities.