EVALUATION OF HAIR DAMAGE 353

354 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS FI(% 100- 20' (a) Unbleached 0.4 0.9 1 '3 118 212 DISTANCE ( mm ) FI(%) 1 2O 0 0.0 0.4 0.9 1.3 1.8 2.2 DISTANCE (mm ) FI(%) 100' (C) 6% H202, 4 h FI(%) 100 t 40' 20' (d) Bleach creme, 30 min o o.o 0.4 0.9 1.3 1.8 2,2 o. 0.4 0.9 1,3 1.8 2,2 DISTANCE (mm ) DISTANCE (mm ) Figure 3. Longitudinal fluorescence intensity scans of unbleached and bleached hair fibers treated with Rhodamine B. The wetting force is given by equation 1: F w = PCrzv COS0 a (1) where P is the fiber perimeter, Crzv the liquid surface tension, and 0a the advancing contact angle. The fiber perimeter is measured with hexadecane in a separate experi- ment, and the liquid surface tension is measured with a platinum wire. Work of adhesion, W, used in this work as an index of surface energy, is defined in the present context as the work required to separate a solid/liquid system at the interface: W = Crzv (1 + COS0a) (2) Figure 7 shows the effects of various oxidative treatments on the wettability of hair fibers. The repeated short time treatment in 6% H202 (2' X 10) and the bleach creme treatment are similar in their effects on water wettability, approaching surface energy levels close to that of the one hour treatment in 6% H202. The two minute bleach treatment repeated ten times has a total bleaching time of 20 minutes. Since the bleaching solution is most effective at the start of the bleaching treatment, and a fresh solution was used at each of the ten treatments, it seems reasonable that this sample would show greater change than one subjected to a single 30 minute bleach treatment. The bleach creme treated sample had a W value in agreement with other 9% H202