CUTTING OF BEARD HAIR 589 (•) -- Fiber 1 (•) - Fiber 2 10 0 20 25 30 35 40 45 50 55 60 65 70 Temperature o C Figure 7. Temperature (oC) vs. force to cut (g) on same fiber (wet) Si•nilar studies of wet beard hair were conducted by measuring the cut- ting force of thoroughly hydrated fibers which ,vere maintained at the de- sired temperature by playing a stream of warm water on the fiber positioned in the jig. Two fibers were each cut about 10 times at each of 4 or 5 tem- peratures, and the results are shown in Fig. 7. The computed least square slope indicates that the f-t-c is lowered by 0.051 g/øC. These data demon- strate that shaving should be easier at elevated temperatures.

590 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS • 7 x ß x-x j-j 40øC o - o 55•C x ß ! ß x o o 1 2 3 4 5 Time (Minutes) Figure 8. Force to cut as a function of time of hydration of beard hair in dilute (0.5 per cent) sodium ]auryl sulfate at different temperattires In a third study the influence of temperature on beard hair hydration time was determined in the presence of a wetting agent (0.5 per cent sodium lauryl sulfate). In view of the number of cuts required, it was necessary to use dif- ferent hairs at different temperatures the fibers were selected to exhibit the same dry cutting force at room temperature. Nevertheless, one anomaly oc- curred in the data at 30øC. All the data are summarized in Fig. 8. It is ap- parent that the time required for full hydration is shortened by increasing