Detergency evaluation. I. Wash test methods

Summary Soil removal data were developed for five laboratory methods and one practical wash test method, utilizing a single standardized soil test fabrie. The degree of correlation between the methods is good considering the variety of machines and procedures used. Better correlation between methods was obtained in hard than in soft water, attributable to the higher solution concentration used in the hard water tests. The rating given the four detergents by the test methods was fairly uniform; the hard water data again were more concordant. Under the conditions used which were optimum for soap, the order of effectiveness was: soap, built nonionic and built alkyl aryl sulfonate, and loralkyl sodium sulfate. Ordinarily, solution concentration‐water hardness curves would be developed for complete evaluation, but the scope of this work precluded this procedure. The test variation for the five laboratory methods was of the same degree. The practical concentional washer test gave coefficients of variation roughly triple those for the laboratory methods. This difference is largely attributable to poorer test control of conditions such as degree and kind of soil of the test load. Even though different test washing machines were used, it appears that adjustment of factors such as wash time and ratio of fabric to solution might provide closer correlation between methods.