582 JOURNAL OF COSMETIC SCIENCE Finally, Fig. 6 shows combing force plots obtained with a hair swatch as it transitions from wet to dry. A close inspection to any one of these plots shows the typical jumping irregularities that characterize a force v.s. comb displacement measurement. The irregularities appear all along the curve and resemble rather the shape of a ''tooth saw". This type of mechanical noise observed almost in any friction process is well docwnented and is due to a stick-slip mechanism typical of systems that present large differences between their static and dynamic friction coefficients. The plots show that as the hair swatch dries the size of the irregularities decrease indicating a decrease in the magnitude of the stick-slip effect. In fact, as it will be discussed later, during the combing friction process the hair fibers are also deformed elastically during the combing friction process and this effect accounts for the appearance of the stick-slip phenomenon. References 1) R Robbins, "Chemical and Physical Behavior of Human Hair" 3th. Ed. Springer-Verlag, New York, 1994, pp. 211-206 2) Y K Karnath, HD Weigmann, "Measurement of Combing Forces", J. Soc. Cosmet., Chem., vol. 37, n°3, pp. 111-124, (1986) . ... t ;,alha,QA{jf MU �- fiU I � !N ,., , ... ..,. ___ ,.,._,✓ ... .. ·•·◄ a,7 It.I nu 11U' 1"-i ,.,., C.�t !11l1 Fig. 1) Comparison of plots of comb/force displacement of hair swatches with normal cut at 90° and cut a 45°. .. .... ffl .. t 1- i- - ""' »II M * - ,i., ""' :m �� Fig. 2) Plots of Peak Areas v.s. corresponding Peak Force for various degrees of tangling for a hair swatch untreated (control) and treated with a commercial conditioner.

2007 ANNUAL SCIENTIFIC SEMINAR Fig. 3) Plots of the ascending half section of tangling peaks for control swatch and after treated with a commercial conditioner. - -� ,..r -� Fan:t ��- ,oor , ....... -�---- Fig. 4) Typical tangling peak with half of its area shaded -r . ., . . � ! NI!' ���·- , i � -:�-· �i ! ..l � --"· =- �- :--� , =---=--- � ,,,tj\ ., �\ � ni � ... __.. ..... /�\ ....... ,____ .... t-.�·-· - - jJ _ ��_.- Fig. 5) Typical tangling peak de-convoluted into two of its main peak components for further analysis t\A Tran1idon wet le ck-y 1ft.ll · _,ll 583 Fig. 6) Plot of Force vs. Comb displacement showing changes in forces as the hair swatch transitions from wet to dry.