J. •o½. Cosmetic Chemists, 17, 171-179 (1966) Instrumental Method for the Determination of Hair Raspiness WILLIAM C. WAGGONER, Ph.D., and GEORGE V. SCOTT, Ph.D.* Presented December 1, 1965, New York City Synopsis--As comb teeth arrange hair fibers in a parallel manner and rub along hair scales, vibrational frequencies are emitted and play a role in the "feel" of hair. The audible fre- quencies, which denote raspincss, may be cosmetically undesirable. In an attempt to record and evaluate hair raspiness, an electronic comb, specifically designed to pick up frequencies by contact, was constructed. Several groups of hair tresses, which were treated with cos- metic chemicals, rinsed and dried, were combed with the instrument. Computer analysis of the data showed the expected differences between tresses and some differences reflected excellent probabilities of test reproducibility. The method lends itself to rapid laboratory screening of agents designed to reduce friction during combing. Hair raspiness, which is the property of a substance producing grating, harsh sounds and feel, is probably most noticeable during the combing process. As the comb moves through the hair and arranges it in a parallel manner, friction at the tooth-hair interface generates fre- quencies and conveys to the individual an impression of general hair condi- tion. It has been shown (1) that subjective judgments of handle and combing ease correlate very well with frictional measurements. A litera- ture survey (2) has revealed the existence of many fiber frictional meas- urement methods, some of which may be applied to human hair studies. Others (3, 4) have measured the spectral distribution of sound produced by fibers in friction. In an attempt to investigate characteristics of hair sound and feel as experienced by an individual during the combing process, an electronic * Colgate-Palmolive Co., Research and Development Dept., Piscataway, N. J. 08854. 171

172 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISFS •- .. ,•.._ :. ...... -*• "-:•'.•:,, ? .:, •'• :•. ß ¾•. ......,.:•:.:. :.:. :: '• •' • • "• ::'., . .'7 .. ß ',:. • •.•, .... . . ....... i m'""•' •' t: •.:.•::' •,:::•2':. z:•.,. .... ......... :&'A.:.--' Figure 1. Co•nb, microphone. and pre-amplifier comb which measures frequencies generated by tooth-hair interface friction was developed, with the following objectives' a. The-method should quantitatively compare product effects on hair raspiness. b. The results should be in a form suitable for the application of sta- tistics. c. The method should be practical enough in test conditions to pro- vide a routine evaluation of hair products. d. The method should provide an additional parameter for tress quality control. MATERIALS AND METHODS A crystal contact microphone* which is specifically designed to pick up frequencies by contact and at the same time remains oblivious to ex- traneous noise was chosen for the study. An Ace Waveserra hard rubber comb (#1033)1 was affixed to the contact microphone (Fig. l) by two small bolts. A third bolt, which had been placed through the comb * HaTnlin, Inc., Lake Mills, Wis. t Ace Comb Co., Butler, N. J.