98 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS 5O 40 3O 2O 10 Set Intact Hair NSA Treated Hair 40oC 70øC Setting Temperature Figure 6. Heat setting of NSA-treated hair. and 70øC of NSA-treated fibers using the coil-setting technique (11). The results are also in accordance with data obtained in an earlier (12) investigation on hair setting. CONCLUSIONS 1. By simple capillary insertion, the pendulum technique can be used for measurement of torsional properties of fibers in both air and liquid media. 2. The results of torsional measurements of hair of different diameter indicate that the hair cuticle is plasticized by water to a greater extent than the hair cortex. 3. Dry heating of hair leads to a small but measurable and long-lasting increase in torsional rigidity. 4. Changes in the torsional rigidity of fibers attendant upon their chemical modifi- cation provide valuable information regarding wet configurational stability of hair and the potential for their settability. REFERENCES (1) H. Bogaty, Torsional properties of hair in relation to permanent waving and setting, J. Soc. Cosmet. Chem., 18, 575 (1967). (2) M. Feughelman, A two-phase structure for keratin fibers, Text. Res. J., 29, 223 (1959). (3) J. B. Speakman, The reactivity of the sulphur linkage in animal fibers--Part I. The chemical mechanism of permanent set, J. Soc. Dyers and Colourists, 52, 335 (1936).

TORSIONAL BEHAVIOR OF HAIR 99 (4) P.S. Hough, J. E. Huey, and W. S. Tolgyesi, Hair body, J. Soc. Cosmet. Chem., 27, 571 (1976). (5) L. J. Wolfram and M. Lindemann, Some observations on the hair cuticle, J. Soc. Cosmet. Chem., 22, 839 (1971). (6) J. B. Speakman, The rigidity of wool and its change with adsorption of water vapor, Trans. Far. Sot., 25, 92 (1929). (7) L. J. Wolfram, J. Soc. Cosmet. Chem., 35, 229 (1984). (8) L. J. Wolfram, K. Hall, and I. Hui, The mechanism of hair bleaching, J. Soc. Cosmet. Chem., 21, 875 (1970). (9) M. Feughelman and T. W. Mitchell, The torsional properties of single wool fibers--Part II, Text. Res. J., 31, 455 (1961). (10) C. H. Nicholls and J. B. Speakman, The adsorption of water by wool--Part IV. The influence of combined acid on the affinity of wool for water, J. Text. Inst., 45, T267 (1954). (11) L. Albrecht and L. J. Wolfram, Mechanism of hair waving, J. Soc. Cosmet. Chem., 33, 363 (1982). (12) P. Sokol, unpublished observations.