Measurement of the skin-cleaning effects of soaps

In the past 30 years, many tests for assessing the irritancy of soaps have been introduced, but only very few tests for evaluating their cleaning properties. The urgent need for such a method is obvious.

The method is based on the principles developed by Schrader, with substantial modifications. As in Schrader's method, we used a fat-based ointment to emulate "dirt." The washing process was performed by placing the examined hand in a rotating soap solution for 5 minutes. The capacity of various soaps to remove the "dirt" was assessed by comparing the sebumeter readings before and after the washing process. The difference between the two readings provided a quantitative estimate of the percentage of "dirt" (ointment) that was washed off during the process.

The cleansing capacity of two soaps was compared to that of water. Soap 1 showed a cleansing of 81.7 +/- 2.4%, soap 2 a cleansing of 75.3 +/- 2.9%, as compared to water of 29.7 +/- 3.4%. The curve representing the distribution of the data was very smooth, bell-shaped and symmetric about its mean. The difference between the cleaning activity of the two soaps tested was statistically significant (P < 0.0001).

We have presented a new method for testing the cleansing capacity of soaps. We believe, that our method gives better results than that of Schrader; in particular, it enables us to discriminate more effectively among the various soaps. Our results indicate that the method is reliable and reproducible. It is also practical, easy to perform, does not require an expensive and complex washing machine, and can be carried out in every laboratory.