134 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS la.I LO 1.0- 0.5 ÷ ] REDUCTION ] 0 /+0 , [ , I ' I , I , ] • [ , [ , 20 0 H20 [ I RINSE REOXlDATION [ 0 20 25 0 I I RINSE TREATMENT TIMES [rnin] Figure 5. Typical curve for the change of the normalized static force F(t)/F o and the normalized dynamic force AF(t)/AF o during the reduction/reoxidation with 1 M sodium sulfite at pH 6.4 for 40 minutes (1 M sulfite). water (95% conf. limits). In all cases the difference increases during the first rinse and increases further with reoxidation. Only slight changes of the normalized forces are observed for the second rinse. Table I summarizes the final values for the relative static and dynamic forces and the values for the initial recovery, R o, and the initial set, So, calculated according to equa- tions 16 and 2 where, with respect to equation 15, Fr•/F o = F(t t4)/F o and AFro/AF o --= AF(t t4)/AF o. H20 H202 H20 REDUCTION 1. R I NSE REOXlDAT[ON 2. R I N 5E lOO 50 A BC D ABC D ABC D ABC D F(t•) AF(tl) F(t2) AF(t2) Fo •Fo Fo •Fo A BC D A BC D ABCD ABC D A BC D A BCD F(t3) AF(t3) F(tz,) AF(tz,) F(ttz,) AF(ttz,) Fo •Fo Fo •Fo Fo •Fo Figure 6. Relative static and dynamic forces at the end of each treatment step for various reducing agents (95% conf. limits). A: 0.3 M TA B' 1 M TA C: 1 M Cys-HCL D: 1 M sulfite.

EXTENSION OF PERMED HAIR 135 R o 70 ! % 60- 50- 30- 20- 0.3 M TA J 1 M $u[fi*.e T T • Cys- HCL 1MTA / --" Figure 7. Relation between the measured and calculated recoveries R i and Ro, respectively, for the four conditions applied. The bars indicate the standard errors of the mean values. The solid line is the regression line for the three more concentrated solutions. Table I also gives the values for the length set, St, acquired by the fibers during the treatment. The length set, St, if any, is small compared to the predicted set, So. The 95% confidence limits for S t in all cases include the value zero. Table II summarizes the bending recovery values, Ri, measured for the hair rings ini- Table I Data for the Relative Static and Dynamic Forces F•/F o and AFro/AFo and the Length Set S L Measured After the Treatments Under the Various Conditions and the Recovery and Set Values, R o and So, Calculated According to Equations 16 and 2 Conditions F•/Fo AFro/AFo Ro, % So, % SL, % O.3 MTA (7) • 0.58 0.92 63 37 5 SE 0.029 0.02 o 2. 2 12. 2 MTA (6) • 0.27 0.88 30 70 SE 0.03o 0.025 2.8 M Cys-HCl (9) • 0.51 0.94 54 46 SE 0.021 0.01 o 2.1 M Sulfite (9) • 0.52 0.86 61 39 SE 0.019 0.012 2.1 9 13.1 6 7.5 17 Means and standard errors, number of determinations in parenthesis.