J. Soc. Cosmetic Chemists, 19, 849-862 (Dec. 9, i968) A Permanent Wave its Performance and of Action Neutralizer: Mechanism J. LEON LICHTIN, Ph.D.,* A. WILLIAM FORBRIGER, Ch.E.,} and C. R. REISS, M.S.E.-• Presented December 6, 1967, New York City Synopsis--A bromate-based permanent wave neutralizer, modified by the addition of at least 24% magnesium sulfate (U.S.P.), has been found to improve the stability of waved tresses in water and, more markedly, in air. A determination of its mechanism of action indicated a combination of effects responsible for its beneficial action. Among these effects are: charge neutralization, uptake of the added salt, and re-formation of hydrogen bonds. To be effective, the added salt must be applied concomitantly with the oxidant, thus re- forming both disulfide and secondary bonds at the same time, a process labeled "parallel waving." The modified neutralizer, compared to bromate, appears to produce a greater degree of hydrogen bond re-formation which (together with its other effects) demonstrates how secondary bonding can promote improved waving performance. INTRODUCTION Permanent waving in its simplest aspect consists of wrapping the hair on a mandrel and then treating it chemically to break down the primary (disulfide) and the secondary (salt and hydrogen) linkages of the keratin, this breakdown followed by the re-formation of these same linkages (1). In the formulation of solutions for permanent waving, the prime con- cern has been the ability of reagents, suitable for human use, either to * College of Pharmacy, University of Cincinnati, Cincinnati, Ohio 45221. t The Realistic Company, 3274 Beekman Street, Cincinnati, Ohio 45223. 849

850 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS sever or to re-form these bonds. In most instances, both types of bonds are broken by a combination of a thioglycolate salt (which reduces the disulfide to sulfhydryl) and an alkali, such as ammonia, which breaks the secondary bonds and permits the hair to become hydrated. The re- formation of the bonds has generally been effected by oxidation, either by air or by a solution, termed a neutralizer, which contains an oxidant (1). The neutralizing solution ideally should re-form all the p•eviously severed bonds. It is expected to restore at least the disulfide bridges from the sulfhydryl groups. The degree, however, to which this type of neutralizer is capable of re-linking severed secondary bonds is a moot question. To the extent that the re-formation of the linkages originally severed in the waving process is less than complete, the hair may lose strength and stability in either air or water, or both. Such loss of stability was considerably evidenced by tresses waved with thioglycolate followed by an oxidant-based neutralizer. In water, the tresses contracted and rear- ranged their curl patterns in air, they drooped and lost their curl. Since air (dry) stability of hair is said to depend strongly on the hydrogen bonds (2), apparently the waving process would be improved if the oxi- dant neutralizer could be made to achieve a greater degree of hydrogen bond re-formation. The question arises whether the neutralizer can be formulated to achieve a greater degree of curl strength and stability. Observations of the performance of a bromate-based neutralizer containing a high per- centage of salt indicate that this is possible. The waving performance of such a neutralizer is, therefore, reported in this article together with a study directed toward determining its mechanism of action. These results demonstrate how re-formation of secondary bonds may be aug- mented by the neutralizer and how this, in turn, increases the stability of the wave. While searching for substitutes for neutralizing agents usually used in permanent waving, it was observed that a solution of calcium acetate when used as a neutralizer on hair previously waved with alkaline thio- glycolate conferred good air stability (or droop resistance) on the tresses however, these tresses relaxed in water. Those waved with the usual sequence of thioglycolate:oxidant, when placed in water, were re- sistant to relaxation. The individual hairs, however, tended to unwind and then rewind into the characteristic helical shape. Though resistant to relaxation, these tresses were not as stable as the ideal tress desired, that is, one which in water would not move at all.