368 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS 10. Swelling in Formic Acid Volume swelling of beard and scalp hair fibers in 97% formic acid was determined according to Caldwell and Milligan (19). The diametral swelling of beard and scalp fibers of comparable diameters was measured on microbiological culture slides, in 97% formic acid, under a coverslip, at one minute intervals, in the view of the light microscope. Figure 5. Scanning electron micrographs of typical Caucasian scalp hairs (A) and beard hairs (B, C, D). Magnification 300x.

COMPARISON OF BEARD AND SCALP HAIR 369 11. Permanent Set The percent set imparted to scalp and facial hair fibers of similar diameters, when treated at 30% extension in boiling 5% sodium bisulfite for 30 minutes, followed by 30 minute relaxation in boiling distilled water, was determined. At least four fibers per sample were analyzed and the values averaged. 12. Supercontraction The contraction of hair fibers, when treated in the relaxed state, at the boil, for 30 minutes with 5% sodium bisulfite, followed by 30 minute relaxation in distilled water at room temperature and air drying, was calculated. Four fibers per sample were analyzed.

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