PERMANENT WAVING 723 I Minutes 40 0 '----Cys tin e 60 80 100 120 140 160 Figure 3. Chromatogram (tracing) of reaction products from cystine and thioglycolic acid incubation Table I Acid Permanent Wave (1/2)t--Process t--Process 2t--Process Amino Acid Control Midpoint Final Midpoint Final Midpoint Final Lysine 2.4 2.2 2.2 2.2 2.3 2.2 2.2 Histidine 0.9 0.7 0.7 0.6 0.8 0.7 0.8 SAE-CySH 0 2.1 0 3.0 0 4.0 0 Arginine 6.6 6.6 6.2 6.8 6.2 6.3 6.6 Cysteic Acid 0.4 0.4 0.8 0.6 0.7 0.4 0.7 CMT-CySH 0 0.2 0.5 0.3 1.3 0.4 0.5 Aspattic acid 5.5 5.4 5.3 5.6 5.4 5.5 5.4 Threonine 7.9 7.7 7.6 8.0 7.6 7.6 7.6 Serine 12.2 12.6 12.3 11.7 13.0 12.5 12.2 Glutamic acid 12.3 12.2 12.4 12.9 12.4 12.5 12.4 Proline 8.3 8.4 8.7 8.5 8.2 8.6 8.6 Glycine 6.1 6.7 6.5 6.3 6.8 6.7 6.2 Alanine 4.7 4.9 4.7 4.6 4.8 4.9 4.6 Half-Cystine 15.5 13.0 14.7 10.5 13.6 9.8 13.8 Valine 5.1 5.2 5.1 5.5 4.8 5.4 5.5 Methionine 0.3 0.5 0.4 0.4 0.8 0.9 0.5 Isoleucine 2.3 2.2 2.2 2.6 1.9 2.4 2.6 Leucine 5.9 5.9 6.1 6.4 5.9 6.3 6.2 Tyrosine 2.1 2.0 2.0 2.1 2.0 1.9 2.0 Phenylalanine 1.6 1.5 1.5 1.5 1.5 1.5 1.5

724 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table II Alkaline Permanent Wave a (1/2)t--Process t--Process 2t--Process Amino Acid Control Midpoint • Final Midpoint Final Midpoint Final Lysine 2.4 2.3 2.2 2.3 2.2 2.3 2.3 Histidine 0.9 0.6 0.7 0.7 0.7 0.8 0.7 SAE-CySH 0 3.9 0 6.7 0 4.6 0 Arginine 6.6 6.3 6.7 7.0 6.0 6.4 6.6 Cysteic acid 0.4 0.4 0.9 0.5 0.8 0.4 0.7 CMT-CySH 0 0.5 1.6 0.6 1.0 0.5 1.9 Aspattic acid 5.5 5.3 5.5 5.4 5.7 5.4 5.4 Threonine 7.9 7.5 7.8 7.8 7.6 7.8 7.6 Serine 12.2 12.7 11.4 12.3 11.0 12.3 11.6 Glutamic acid 12.3 12.2 12.4 12.2 12.9 12.5 12.4 Proline 8.3 8.6 8.5 8.5 8.9 8.6 8.8 Glycine 6.1 6.8 6.3 6.6 6.8 6.5 6.5 Alanine 4.7 4.9 4.8 4.8 4.7 4.9 4.8 Half-cystine 15.5 10.4 11.9 6.8 10.8 9.5 12.6 Valine 5.1 4.8 4.9 5.0 5.8 4.9 5.2 Methionine 0.3 0.7 0.6 0.7 0.6 0.5 0.4 Isoleucine 2.3 2.2 2.5 2.3 3.0 2.2 2.4 Leucine 5.9 6.0 6.4 6.1 6.6 6.1 6.1 Tyrosine 2.1 2.0 2.1 2.1 2.1 2.0 2.0 Phenylalanine 1.6 1.6 1.7 1.6 1.7 1.6 1.6 aAmino Acids are expressed in moles/100 mol. bHair was treated with ethylene imine for 2 hrs after reduction step. which elutes slightly after alanine but definitely before cystine (peak IV). The latter has a ratio of 440 to 570 nm similar to the mixture disulfide and may represent a mixed disulfide of cysteine and dithioglycolide. The effect of processing time variations are shown in Tables I and II. The only amino acid that is significantly changed during processing in cystine. The decrease in this can be monitored accurately by covalently trapping the cysteine formed during the reduc- tion step by reacting immediately with ethyleneimine to yield the stable derivative, SAE-cysteine. These values are shown in Table III for under, normal, and over processed waves. The reduction increases in relation to the time of processing in the acid waves done on swatches. In the optimally processed acid wave 19.4 per cent of the cystine is reduced to yield a good wave as shown by test curl pattern. The alkaline swatch shows faster and greater reduction with a t-reduction of 43.2 per cent of the cystine. Overprocessed hair with the alkaline wave contains less reduced cystine than the normal time. This may reflect some spontaneous reoxidation or possibly a pH change occurring with the longer time as the thioglycolate is used up. The figure of 43.2 per cent is high, but was reproducible. Other figures for typical reduction levels in the salon are shown and do vary between 17.3 to 43.2 per cent. Levels found in the lab correlated with those waved in the salon. The chemical changes in the disulfide crosslinks are also reflected in the stress-strain data seen in Table IV. The hair had an average diameter of 59/am and has normal values of 29.9 + 5.4 S.D. grams force and percent elongation of 39.6 --+ 1.2 S.D. before processing. When hairs were pulled at «t without reoxidation, the grams force