Laboratory Study of Factors Influencing Milestone Formation

Abstract

Summary Through use of an Autotechnicon, an instrument which dips test pieces into and out of a series of solutions, a reproducible method for forming milkstone on stainless steel was developed. Milkstone quantity increased with increase of temperature of water used to rinse milk; increasing the drying time before or after this rinse did not influence milkstone formation. Interrelated chemical factors involved in producing milkstone were milk, water hardness, chlorine solutions, and cleansers. Water hardness was singly the most important factor and a nonlinear increase of milkstone with increasing water hardness was demonstrated. There was little difference in milkstone amounts formed either with sodium or with calcium hypochlorite; formation of less milkstone with chlorinated trisodium phosphate possibly could be attributed to water softening caused by hard-water salt precipitation. Of the cleansers tested, least milkstone was produced with an acid, slightly more with a neutral nonionic detergent, still more with one containing trisodium phosphate and pyrophosphate. Comparison of synthetic detergents indicated that a cationic helped produce about twice the milkstone formed with a non-ionic or an anionic. Inorganic cleanser constituents producing clear hard-water solutions helped form less milkstone than those producing cloudy solutions.