290 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS recently (1) showed that 36•o of all women between the ages of 16 and 24 had long hair and of those interviewed, 71•o would have grown their hair longer had it not been for the problems involved. It is significant that two of the most widespread problems associated with long hair are the tendency for tangles to form during combing and the presence of split ends. Human head hair has a growth cycle• of between 3 and 6 years and reaches a final length before natural shedding, and providing it is not cut, of 50-80 cm. During this growth period the exposed fibres undergo pro- gressive change which is generally referred to as weathering. The predominant cause of this deleterious change is thought to be sunlight and this results in a variation in the chemical and physical properties from the root to the tip of the fibres (2-4). In addition, cosmetic treatment and handling during brush- ing and combing increase the effects of environmental exposure. It is well known that in extreme cases of over-treatment with certain cosmetic agents or over-exposure to sunlight, premature fracture of the hair may occur resulting in a condition referred to by dermatologists as trichorrhexis nodosa (5-7). This is commonly known as 'paint brush hair' because of the longi- tudinal fibrillation or separation of the hair cortex which gives each hair the appearance of the bristles of a paint brush. It is interesting to note that these structural characteristics are similar to those encountered in the split tips of moderately weathered hairs. The present paper is concerned with a study of the fracture of human hair and an investigation of those processes which lead to longitudinal splitting of weathered hair. Because of its moderately high resolution, its wide range of magnifications and high depth of focus, the scanning electron microscope (SEM) has been used exclusively in this work. Novel techniques have been devised for stressing fibres in the microscope in such a way that the fracture process can be followed continuously at high magnification and the results recorded on video tape. Although the video tape results will be shown at the actual Symposium it is only possible in the present published paper to show a representative selection of static photographs. AN EXAMINATION OF HAIRS FRACTURED FROM ROOT TO TIP The hair of six young women was chosen for use in our experiments. The hair was in excess of 50 cm length and varied in the extent of weathering as assessed by loss of surface cuticle and the presence of split ends (8). Hair

JOURNAL OF THE SOCIFTY OF COSMFTIC CHEMISTS 1o•in 5 Figures 1-5. Examples of the type of fracture observed from the root end (Fig. 1) to the tip end of severely weathered hair (Fig. 5). Facing page 290