EFFECT OF GROOMING ON HAIR CUTICLE 213 hair, but the amount of damage is seen to be greatly increased by the introduction of the process of wet-combing. It is also clear that this damage is reduced significantly by the use of a conditioner. A reduction in the rate of damage with grooming by the use of a conditioner of 13% for Hair 1 and up to 82% for Hair 2 was observed. The "on-head" trials confirm the tress results, illustrating again the beneficial value of the use of a conditioner. In addition these results show that brushing is much more damaging than combing. The mechanism by which a conditioner reduces damage to the cuticle during grooming is postulated to be a dual one. Firstly, it would provide the lubrication necessary to reduce the friction in the hair during combing and hence reduce the strength of the abrasive forces to which the weakened wet hair is subjected. Secondly, by preserving the cuticle in this manner the conditioner probably also serves to reduce the following degree of entanglement which occurs during shampooing. This would result in less damage being incurred by the subsequent wet combing. This latter postulate is prompted by the observation made during the tress experiments that the better the condition of the hair, the smaller was the degree of entanglement that occurred during grooming. In order to confirm the friction reduction effect a number of measurements of the work done during combing were carried out on a tress of hair using an Instron Tensile Tester ©. The technique used was similar to that employed by Schoenberg and Scafidi (10). The treated tress was pulled through a metal comb at a constant rate of 1000 mm/min, and the area under the force versus distance travelled curve was integrated to determine the work done. The work done when the tress had been treated with conditioner after shampooing was compared to that done on shampooing only with sodium lauryl ether sulphate. Four different types of conditioners were tested with the tress being subjected to minimal tangling during shampooing, an excess amount of conditioner applied and worked through the hair, and rinsed thoroughly before testing. One of these conditioners was also tested with the conditioner left in the hair for combing, both with minimal entanglement and with some degree of entanglement. The results obtained are given in Table II. Table II The Relative Work of Combing Conditioner Relative Work of Combing A 28 B 29 C 27 D 35 None 100 B 46* B 77** Conditioners A, B, C and D are commercial products based on quarternary ammonium compounds and fatty alcohols. They were rinsed out before combing. A also contains a cationic protein. It is the conditioner used in the preceding experiments. *Conditioner left in hair (no rinse) *Hair deliberately tangled. Conditioner left in hair (no rinse) All results are based on an average of four measurements.

214 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS It can be seen that there is a significant reduction in the work done during combing of between 33% and 73%, with the conditioner appearing more effective when there is minimal entanglement and when it is rinsed out of the hair first. As it is probable that a layer of the conditioner remains on the hair fibres after rinsing, then rinsing the hair should make no difference to the hair-hair and hair-comb friction forces generated. It is therefore likely that the smaller work reduction observed when the conditioner is left in the hair is due to the greater resistance to combing offered by the presence of the fairly viscous conditioners themselves. The results thus do indicate that conditioners are very effective in reducing the friction forces present in the hair during combing. Additional complications arise when the hair is deliberately tangled during shampoo- ing. This frequently gives rise to the formation of knots and, during combing on the Instron, © if these knots do not unravel fairly quickly they will often be broken off because the hair continues to be pulled through the comb at a constant speed. This means that it is the breaking strength of the hair fibres involved that is being tested rather than the friction forces and can lead to an artificially high work value. Although knots do form in practice this method of testing is not a good approximation of what occurs during combing in practice. Generally the knots will be gently worked out rather than the comb being dragged straight through and breaking off the hair. It was observed in the tress experiments that the presence of a conditioner did make this untangling process easier. It is obvious from the preceding discussion that the condition of the hair cuticle can be greatly improved by the use of correct grooming techniques. This is especially important to the overall appearance of the hair since the condition of the cuticle probably has a large influence on such factors as the shine, body, and manageability of the hair. Obviously, washing and drying the hair cannot be avoided, but by using a conditioner and combing rather than brushing out the knots much of the usual damage can be avoided. CONCLUSION These observations have again verified that the normal grooming processes to which hair is subjected can cause severe damage to the hair. This study has shown specifically that the processes of wet combing or wet brushing out of the knots introduced during shampooing and towel drying are a particularly serious source of this damage. It was shown that shampooing and towel drying alone can damage the cuticle but that the wet-combing or brushing out of knots greatly increases the damage. Although only one subject participated in the "on head" study the results indicate that brushing may be far more damaging than combing. This study found that the normal shampooing process, involving shampooing, towel drying, and wet combing out the knots, can abrade away the cuticle at a rate of I to 2.5 cuticles per 50 treatments. This means that when this grooming procedure is undertaken twice per week the 6 to 10 cuticle layers which are the normal range encountered in human hair can be removed in 14 to 60 months. Hence this grooming process can account totally for all the damage done to the cuticle, and this damage can be inflicted in a period of little over one year in some cases. This appears to be a much greater cuticle removal rate than the 5/am abrasion per 2000 dry comb strokes reported