JOURNAL OF COSMETIC SCIENCE 144 We tested the infl uence of hair status on the hair breakage by combing virgin and chem- ically damaged hair (bleached and permanently waved). Several anti-breakage shampoos from the market containing silicones were examined and found to be effi cient in terms of hair breakage protection. As silicones are often regarded less sustainable and biodegradable compared to oleochem- ical ingredients and the usage of silicones in shampoos is very much limited by patents, silicon-free alternatives for anti-breakage effi cacy are of considerable interest. Therefore, several waxes were tested for their deposition on the hair from shampoo formulations. This approach is straight forward also because waxes are often used for shampoos to give them a nice milky or even pearlescent appearance. Several parameters of wax dispersions were tested for their infl uence on the wax amounts deposited on hair. EXPERIMENTAL HAIR STRANDS TREATMENT All experiments are performed using dark brown European hair (from International Hair Importers, New York). If not stated otherwise the strands were bleached applying 5% of hydrogen peroxide (pH 9.4) for 15 min followed by intensive rinsing. Treatment of the hair with shampoo formulations was performed as follows: 0.25 g formulation per 1 g hair was applied on the hair using dyeing brushes for hair dressers. After 5 min incuba- tion time the strands were rinsed with warm tap water (38°C) using a special rinsing device ensuring a water fl ow of 1 l per minute and strand. The whole procedure was re- peated once. For wet combability, the hair strands were taken directly after the second rinsing, for all other methods the strands were dried. For conditioners a similar procedure was applied, but with a single application and only 3 min incubation time. Perming of hair strands was done applying fi rst a perming solution (7% thioglycolic acid, pH 9.5) for 30 minutes, followed by extensive rinsing and the application of fi xation (2.2% hydrogen peroxide, pH 4) for 30 minutes. Subsequent to extensive rinsing the hair strands were dried with hot air for 30 minutes. The persulfate bleaching was performed by a 30 minute treatment of the hair strands with a bleaching solution (6% hydrogen peroxide, 15% ammonium peroxide sulfate, pH 9.4) followed by extensive rinsing and 60 minutes of hot air drying. HAIR BREAKAGE DETERMINATION A customized system was developed, allowing the parallel combing of up to ten hair strands (see Figure 1). Combing was performed by two combs per strand mounted on a motor-driven axis. The broken hair fi bers were collected in drawers made from stainless steel, one for every hair strand. The device was set in a box allowing the control of tem- perature and relative humidity. Standard conditions were 40% relative humidity and 30°C (to avoid an active cooling system). The amount of broken hair was determined gravimetrically after sorting out fi bers longer than 9 cm (which are most probably not broken but pulled out of the glued part of the

2008 TRI/PRINCETON CONFERENCE 145 strand). The mean and standard deviations of all ten strands were calculated to determine the hair breakage of strands treated with the same formulation. Differences in the means were evaluated statistically calculating a heteroscedastic Stu- dent’s t-test. The difference is regarded signifi cant for p-values 0.05. SPLIT ENDS EVALUATION To determine the amount of split ends, 1.5 cm of the tip section of each strand was cut. The fi bers with split ends were then separated from the intact fi bers by using a special device. It consists of a sieve with a pore size of 200 μm equipped with a cylinder to avoid loss of hair fi bers. For the sieving procedure the sieve was rotated and a counter air fl ow was applied to bring the fi bers in a vertical position. Within 15 min all intact fi bers had passed the sieve, whereas the fi bers with split ends stuck in the pores. The amount of split ends was deter- mined weighing the sticking fi bers and dividing their weight by the weight of all fi bers before the sorting procedure. The mean and the standard deviations of all ten strands were calculated to determine the amount of split ends treated with the same formulation. WET AND DRY COMBABILITY Wet and dry combing performances were determined using a robotic system, combing 10 bleached strands per formulation. The combing work was determined by integrating the force versus distance curve. After determining the baseline values of the strands, they were treated according to the protocol given above. The residual combing work was calculated as ratio of (work after shampoo application) / (work before shampoo application) for each strand. DETERMINATION OF THE AMOUNTS OF WAXES DEPOSITED ON THE HAIR Hair strands were treated with shampoo formulations as described above. Samples were taken out after 1, 3 and 5 treatments. The hair strands were extracted with appropriate Figure 1. Set-up for the parallel combing of 10 hair strands to determine hair breakage.