700 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS the electron irradiation of the fibre prior to treatment. On the other hand we have never observed any change in the surface of hairs during extended examination in the microscope. Also since the fine structure of the surface of a low melting point wax (39øC) did not change under the same conditions as we use with the hairs, heating in the electron beam must be relatively insignificant. Using this technique we have been able to carry out a critical study of the effects of a number of cosmetic treatments on the hair surface. For the first time it has been possible to assess the changes both visually and quantitatively. Figs. 9-12 show identical areas of a single hair before and after a series of combing experiments. In Fig. 9 the initial fibre is seen, and Figs. 10-12 show the hair after 500, 1 000 and 2 000 strokes respectively, of a nylon comb. The lower part of each figure shows enlargements of corresponding scale edges and it is evident that the scale edges progressively break away with combing. The average rate at which the scale margins recede down the fibre by this process is about 0.5 gm after 2 000 comb strokes. It is generally agreed that backcombing damages the hair surface severely. Comparison of Fig. 13 of the initial hair and that of Fig. 14 showing the hair after 200 backcombing strokes with the nylon comb (i.e. the hair mounted with the scales overlapping towards the root end of the switch) reveals that the scale edges not only break away but also tend to be rounded off. It has been our experience that large portions of the cuticle surface are not stripped off during backcombing but rather that edges are rounded off and that the breaking away of small fragments from the scale margins occur far more readily than for normal combing. The effects on the hair surface of perming hair, by treatment with 4•o thioglycolic acid adjusted to pH 9.7 with ammonia for 30 min and then with 2• hydrogen peroxide at pH 4.8 for 10 min, are shown in Figs. 15 and 16. Although there is loss of cuticle by breakage of small fragments from the scale margins, there is gross structural deformation of the fibre this latter result confirms our previous observations (1). Presumably such structural deformation is caused by the breakdown of disulphide bonds within the fibre with concommitant swelling and the inability of the fibre to revert to its original configuration. The effect of bleaching hair with 9•o hydrogen peroxide for 30 min is illustrated in Figs. 17 and 18. In this case there is very little change in the fibre surface structure apart from the occasional breaking away of small fragments from the scale margins.

Figures 9-12. Normal combing. Facing page 700