6O2 JOURNAL OF THE SOCIETY OF COSiViETIC CHEiViISTS Figure 2. Percent Peptide Sorbed 0.,5- 0.4 0.3 30 min Vir• 0.1 o •'•i I • • I I I I 1 2 3 4 5 8 9 10 11 2 6 7 Sorption of peptides from solutions of different pH values by peroxide-damaged hair. (The curves are identified by the time the hair was bleached) one hour. In some instances in which treatment at pH values of 1 to 4 did not appear to show differences, the strands were treated with peptide solutions from pH 4 to 12. Effect of Bleaching on Peptide Sorption at Various pH Levels The curves in Fig. 1 demonstrate the shift in the pH of maximum peptide sorption with extent of bleaching. The curve for unbleached virgin hair shows little peptide sorption from solutions at pH 1 to .5, after which a gradual increase occurs to a maximum at pH 8 to 11 with a slight drop at pH 12. After a five minute bleach period, the maximum appears at pH 8-10 and after ten minutes of bleaching, the maximum drops to 7 and remains at pH 6-7 thereafter, even after bleaching periods of sixteen hours. Sorption increases considerably after only five to ten minutes of bleaching, but for somewhat longer periods of time (fifteen to thirty minutes) there is very little further increase in peptide sorption, as shown on Fig. 2. After one hour of bleaching an actual decrease in

SORPTION OF PEPTIDES BY HAIR 603 Percent Peptide Sorbed 4.C)-- I I I I I I -- 3.C)-- -- 2.0 Virgin hair 1• 2 3 4 5 6 7 8 9 10 11 12 pH Figure 3. Sorption of peptides from solutions of different pH values by peroxide-damaged hair. (The curves are identified by the time the hair was bleached) the sorption maximum is noted. Still longer bleaching periods (two hours or more) again cause the sorption maximum to increase to higher levels, as shown in Fig. 3 which shows a larger scale graph covering bleaching periods, from one to sixteen hours. A similar anomalous effect was noted, for a different time period, in the case of virgin hair strands treated with ammonium thioglycolate, as will be described later. It is in all probability due to differences in susceptibility to oxidation as well as differences in sorption capacity between the cuticle and cortex of the hair. A short bleaching period may be sufficient to soften the cuticle and open up a large surface area as the scales loosen. Once the cuticle has tmen penetrated or removed, action on the more compact cortex begins, although it appears to be considerably more resistant to attack than is the cuticle layer. How- ever, once the cortex has been extensively degraded, sorption of peptide increases to a very high value. Figure 4 summarizes the results of an experiment on the removal of peptide, sorbed on hair at pH 6 by buffers at other pH levels. A group