MEASUREMENTS ON HUMAN HAIR 381 i•- , , OIIITANCE FROM TOP (CM) 0 Figure 1. Dry combing curves, B before treatment, A after treatment with com- mercial creme rinse. Combing loads ap- pear plotted against distance of comb from top end of swatch IO n • eo 0 0, e= u i i i i ! ...... ' ' ' Im I0 5 0 ITANCE FROM TOP (CM) Figure 2. Wet combing curves, B before treatment, A after treatment with com- mercial creme rinse. Combing loads ap- pear plotted against distance of comb from top end of swatch that changes in the values of these parameters are more important and more reproducible than their absolute values. It also follows that great caxe has to be taken so that comparisons-as, for example, before and after the use of a product-are done under experimental conditions that are, insofar as possible, identical. If done carefully, however, this method al- lows us to measure changes in combing forces of the order of -+ 20 per cent. Average changes are calculated by averaging the individual values measured on a set of replicate swatches. Equipment The instrumentation consists of an Instron Tensile Tester (Metric Table Model, TM-M*) to which some attachments have been added (see Fig. 3). The Instron load cell B which has a range of 0 to 2,0'00 g is used. Other re- cording tensile testing instruments could be similarly adapted. The attachments to the Instron Tester shown in Fig. 3 are as follmvs (c) Comb Stand: the comb stand is an L-shaped aluminum part designed to hold different types of combs, it is mounted on the traveling crossbar of the In- stron by means of two screws (b) Comb: the comb used in our measure- ments consists of 8 cylindrical stainless steel teeth (unpolished), 2.2 mm in diameter, mounted (with an interteeth distance of 1.5 mm) on an aluminum frame. Two removable bars of the same material and dimneter as the teeth are *Instron Corp., Canton, MA.

38•, JOUBNAL OF THE SOCIETY OF COSMETIC CHEMISTS I , I cl Figure 3. Part of Instron Tensile Tester showing combing attachments: (a) clamp (b) comb (c) L-shaped stand (d) crossbar (e) hair swatch (f) load cell mounted perpendicular to them in order to keep the hair in place during combing (Fig. 4). (a) Clamps: the hair as used for these measurements is mounted on specially designed aluminum clamps (Fig. 4). These clamps pro- duce approximately rectangular cross-sectional swatches .They have a hole on the top from which they are hung on a 1.5 mm diameter metal rod, which is connected to the load cell of the Instron. At the clamp, the dimensions of the cross-section of the hair swatch are 2.8 cm in length and approximately 2 mm in wi.dth. At least two regular hand combs should be at hand for each measurement. One of the combs should only be used for clean un- treated hair swatches. The other one should be used for the treated swatches. Ordinary hard rubber or nylon combs are suitable. The measurements are done under standard temperature and humidity con- ditions (70 +--2øF, 65-+-2 per cent RH). This requires the availability of a temperature and humidity controlled room wherein the tensile tester can be located and operated.