134 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS sidered the most important and useful test, has been employed extensively. The alkali solubility, copper uptake and hydrogen peroxide sorption tests widely used in the textile industry, were also conducted to provide more information about the physical and chemical changes on hydrogen peroxide bleached hair. BASIC EXPERIMENTAL PROCEDURES Bleach Solution In all of the tests described in this paper, human hair was immersed in hydrogen peroxide solutions for periods ranging from fifteen minutes to four hours. The solutions were prepared by diluting 35 per cent H202 (obtained from the Becco Chemical Division of Food Machinery and Chemical Corporation) with distilled water to 6.0 4- 0.1 per cent and by activating the solution with the addition of 0.5 per cent NH4OH. From preliminary experiments it was found that, when in contact with hair, H20•. decomposes very rapidly. Therefore, it was necessary to stabilize the solution with 0.1 per cent of the dry salt of tetrasodium ethylenediamine tetraacetate dihydrate. This addition was performed to keep the H20• concentration as high as possible during the bleach process (up to four hours), and to chelate any traces of metallic ions on the fibers, which have been reported to increase the fiber damage up to four times (4). All tests were made with dark brown, virgin Italian hair, which had been previously shampooed. Six-inch strands of hair, weighing two grams were used. Twelve single hairs were knotted (four inches between the knots), Figure 1.--Hair bleached for various time periods. The dark brown hair is shown as bleached for 30, 60, 120, 180 and 240 minutes.

PROPERTIES OF PEROXIDE-BLEACHED HAIR 135 TABLE 1.--HdD2 A•r• NH4OH C•A•OES AT 32.2øC. Time, H,,O• % HdD2 % NH4OH, min. No EDTA 0.1% EDTA % pH 0 5.92 6.08 0.50 9.52 15 .. 5.87 0.45 9.36 30 ... 5.79 0.44 9.38 45 5.68 0.44 9.38 60 •.b• 5.60 0.43 9.38 120 3.12 5.06 0.39 9.38 180 2.58 4.67 0.36 9.38 240 2.15 4.31 0.31 9.38 and attached to two-gram strands. These hair samples were immersed in the bleach solution for various time periods at 32.2 + 0.1øC. The weight of hair (grams) to volume of bleach solution (mi.) ratio was 1:25. At the end of the treatment the bleached hair was rinsed in running tap for two minutes (Fig. 1). The addition of 0.1 per cent tetrasodium ethylenediamine tetraacetate stabilizes the bleach solution quite remarkably (Table 1). The fall-off after four hours of processing is 29 per cent of the original peroxide con- centration. Whereas without the sequestrant, a loss of 63 per cent is found during the same time. A comparison of these two solutions may be seen pictorally in Fig. 2. In addition to the stabilizing effect, the se- questrant is capable of chelating traces of metallic ions, which has been reported to cause increased fiber damage in wool. Therefore, it may be assumed that in all tests described in this paper, the bleached hair samples were not affected by any catalytic interferences of metallic ions as reported by Stoves (4) and Andrews (5). "' '?:•!:'!5'7.'•' ,r.: ....... ...:..: •.?. ::5, ß .' ...... .j:..!( ? ..... ß :.a"-• ....... 4.',- 5:•:•.. :..:7 :.•.: ......... .•: ß -- .•: . . -• ,• ..... •5: .• ',¾. 1:•:, '. : ::.• ß :. •..:' .... :5: • •: _:} .:. •:'.: *'*'::. .:• ':' "• ".5.%.•.•:': :. x } ' .... ,. . ..... :,- -,%• • :..•..,:•:• ..? -%:. Figure 2.Comparison between hair sample bleached in stabilized (top row) and unstabilized (bottom row) bleach solution for time periods of 120, 180 and 240 minutes.