EVALUATION OF HAIR DAMAGE 369 cause increases in the rates of diffusion of dyes into hair fibers in our previous work with uranin. However, cross-sectional fluorescence intensity profiles of groomed hair tagged with the fluorescent tracer showed similar diffusion patterns, indicating that subsequent grooming, for ten cycles or a total of 1,000 combing strokes, did not produce significant differences in diffusion rates for either the unbleached or the bleached samples. Mechanicalproperties. Abrasive damage experienced during grooming would be expected to be restricted to the fiber cuticle and possibly lead to its total loss. It has recently been demonstrated (16) that oxidative cuticle damage even under quite severe conditions does not appear to cause a reduction in tensile properties, which supports the hypothesis that the tensile properties of human hair are primarily those of the cortex. In evaluating the original bleached hair, we observed that the nonultimate mechanical properties seem to be more sensitive to oxidative damage than the properties obtained at fiber failure. If damage from grooming sequences is indeed mainly a surface abrasion effect, we would not expect to see significant changes in mechanical properties. On the other hand, the shampoo treatments and intermittent stretching from combing may lead to structural weakening, which could be reflected in both the ultimate and nonultimate mechanical properties. In general, the effects of grooming bleached hair were minor on the mechanical prop- erties of modulus, breaking stress, and work to failure, as seen in Table VIII. The incorporation of conditioner into the grooming process had an alleviating effect on whatever damage was encountered during grooming. Significant differences arose in the evaluation of 20% work and yield stress, however. Improvement in 20% work with the addition of conditioner was clear. In evaluating yield stress for unbleached and bleached hair, we found that shampooing and combing always was most damaging and that the incorporation of a conditioning step into the Table VIII Mechanical Properties of Groomed Hair Modulus Yield stress Treatment (GN/m 2) (GN/m 2 x 10- 2) Work to extend 20% Breaking stress Work to break (MJ/m 2 x 10-•) (GN/m 2 x 10-1) (Mj/m 2) U0 2.8 -+ 0.23* 6.7 +- 0.76 U1 2.8 -+ 0.32 7.0 -+ 0.86 U2 3.0 -+ 0.41 7.0 -+ 1.3 U3 2.9 +- 0.31 6.3 + 0.76 U4 3.1 -+ 0.45 6.6 -+ 1.0 2B0 2.6 +- 0.28 5.7 -+ 0.79 2B1 2.2 -+ 0.19 5.5 -+ 0.55 2B2 2.5 -+ 0.23 5.6 -+ 0.80 2B3 2.6 -+ 0.37 4.6 -+ 0.62 2B4 2.7 -+ 0.26 5.6 -+ 0.51 4B0 2.5 -+ 0.23 4.9 -+ 0.69 4B1 2.5 -+ 0.29 5.0 -+ 0.65 4B2 2.6 +- 0.35 4.7 -+ 0.74 4B3 2.5 -+ 0.23 4.6 -+ 0.50 4B4 2.9 -+ 0.29 5.6 -+ 0.66 4.4 +-- 0.71 3.3 +-- 0.31 2.6 + 0.31 -- 2.4 + 0.37 2.6 +-- 0.37 -- 3.4 -+ 0.64 2.5 -+ 0.58 -- 3.2 - 0.03 2.4 + 0.30 -- 3.4 + 0.46 2.4 +-- 0.40 3.8 +-- 0.79 3.0 +-- 0.32 2.3 - 0.30 -- 2.7 --- 0.26 2.1 +-- 0.29 -- 2.7 + 0.28 2.0 + 0.31 -- 2.7 +-- 0.33 2.0 --- 0.26 -- 2.9 + 0.32 2.4 +-- 0.46 2.7 + 0.27 2.8 +-- 0.32 2.2 + 0.32 2.8 + 0.32 2.9 + 0.36 2.3 --- 0.34 2.7 +-- 0.37 3.0 + 0.41 2.3 --- 0.34 2.6 q- 0.24 2.8 + 0.27 2.2 + 0.28 3.1 + 0.33 3.1 --- 0.32 2.6 --- 0.37 * 95% confidence limits.

370 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS sequence always alleviated that damage. In the case of the four hour bleach treatment, the improvement in yield stress after the application of conditioner resulted in values higher than those of the ungroomed sample. SUMMARY A variety of methods were combined to quantify the extent of primary damage from chemical changes introduced during oxidation of hair. Methods for detecting damage were chosen to evaluate surface or structural changes. Different levels of damage were achieved by changing the time of treatment in 6% H202 or the treatment process (hydrogen peroxide vs a commercial bleach creme). Surface changes increased with peroxide treatment times. The four hour peroxide treat- ment resulted in the greatest surface damage. Surprisingly, the commercial bleach creme caused much less surface (by SEM and wettability analyses) than structural damage. Although structural changes also increased with peroxide treatment time, some methods found the four hour peroxide treatment more damaging than the commercial bleach creme and others found the commercial product most damaging. Additional major structural damage was shown in successive perm treatments on unbleached and bleached hair. We explored the possibility that oxidative damage, as experienced during bleaching of hair, leaves the fibers susceptible to secondary damage during subsequent grooming. Grooming processes were simulated by combing, shampooing, and conditioner treat- ments before combing. We found that combing produced secondary damage and that conditioner use reduced or prevented the damaging effects of combing. Damage from combing was more severe in bleached than in unbleached hair. The application of conditioner after shampooing resulted in less damage in both bleached and unbleached hair. Attempts to correlate the various damage analyses and to draw conclusions about the relative effects of surface and bulk damage are currently underway on an expanded data base and will be the subject of a subsequent paper. ACKNOWLEDGMENTS The work reported here was conducted as part of a project, Analysis and Quantification of Hair Damage, sponsored by a group of corporate TRI/Princeton participants. We acknowledge the contributions of our colleagues, Irene Bradford, Rudy Turner (de- ceased), and Chi Wang. REFERENCES (1) R. Beyak, C. F. Meyer, and G. S. Kass, Elasticity and tensile properties of human hair. I. Single fiber test method, J. Soc. Cosmet. Chem., 20, 615-626 (1969). (2) C. R. Robbins and C. Kelly, Amino acid analysis of cosmetically altered hair, J. $oc. Cosmet. Chem., 20, 555-564 (1969). (3) C. R. Robbins and C. H. Kelly, Amino acid composition of human hair, Text. Res. J., 40, 891-895 (1970).