MEASUREMENTS ON HUMAN HAIR 397 parison with ours. The method developed by Newman et al. (1) is similar to ours. It involves the insertion of a comb into a swatch of hair and the measure- ment of the forces opposing its motion. The authors indicate that after less than a second of comb motion at a rate of 1.5 mm/sec, the combing force reaches a nearly constant vah,e, xvhich is measured. This contrasts sharply with the shape of our combing curves (Figs. i and 2), and indicates that these measurements are being done on hair swatches that, either because of their size and geometry and/or because of the way in which they are handled prior to the measurements, do not get tangled before and/or while they are being coinbed. This approach, although desirable from the point of view of improving reproducibility, is not favored by us, because in reality, tangles are almost always encountered while combing hair, and detangling is an integral part of the function of products developed to improve the combability of hair. Combability measurements have been reported to be in use at Hoffman- LaRoche Co. Laboratory, but the method has not been described in detail. The method developed by Waggoner and Scott (2), which involves the mea- surement and analysis of the sound frequencies generated when hair is combed, although it is an interesting approach, suffers in our opinion from the unnecessary complications introduced by the necessity of having to interpret the generation of sound in terms of combing frictional forces which can more easily and directly be measured in the first place. CONCLUSION The increasingly sophisticated product development taking place in our in- dustry is in need of methods which can objectively measure the effect of prod- ucts on human hair. Although these methods do not completely replace the subjective evaluation of a product's performance, they are obviously of great help in guiding research and in substantiating performance claims made for hair products. Furthermore, by providing quantitative data these methods open the door to the investigation of the underlying physico-chemical phe- nomena involved in the modification of human hair for cosmetic purposes. The combability method described in this paper has proven very useful in our laboratory. The authors hope that others will benefit from its use. ACKNOWLEDGMENT The authors wish to thank Dr. Michael Wong for assisting with the statisti- cal analysis of the data and for his valuable comments during the development of the method. Also, we want to thank Dr. Lee Hunter for valuable insights into the physics of combing. (Received April 30, 1975)

398 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS •EFEI•ENCES (1) W. Newman, G. L. Cohen, and C. Hayes, A quantitative characterization of combing force, J. Soc. Cosmet. Chem., 24, 773-82 (1973). (2) W. C. Waggoner and G. V. Scott, Instrumental method for the determination of hair raspiness, J. Soc. Cosmet. Chem., 17, 171-79 (1966). (3) D. L. Wedderburn and J. K. Prall, Hair product evaluation: From Laboratory bench to consumer and back again, J. Soc. Cosmet. Chem., 24, 561-76 (1973). (4) K. A. Brownlee, Industrial Experimentation, 4th ed., Chemical Publishing Co., Inc., 1953, Pp. 106-8. (5) K. A. Brownlee, Industrial Experimentation, 4th ed., Chemical Publishing Co., Inc., 1953, Pp. 35 & 93. (6) G. V. Scott, C. R. Robbins, and J. D. Barnhurts, Sorption of quaternary ammonium surfactants by human hair, J. Soc. Cosmet. Chem., 20, 135-52 (1969). (7) G. V. Scott, Spectrophotometric determination of cationic surfactants with Orange II, Anal. Chem., 40, 768-73 (1[}68). (8 M. Wong, Clairol Research Laboratories, unpublished results.