PRACTICAL SELECTING METHOD OF WAVE LOTION FOR HAIR DRESSER 35 attached to the bottom of each column. Column A was mounted on the lower jaw of the cross head of a tensile tester, and Column B was mounted on a stand with which the height of the column could be controlled. A single straight hair was exactly fi xed down the middle of Column A through a silicon stopper. Column A could be separated from Column B by shutting the lower jaw and closing the three-way stopcock. All permanent treatments of the fi bers were conducted in Column A. Column B was used to adjust the water level of Column A during measurement of the 20% index. Because the water level in Column A rose and fell with the movement of the cross head, the water level in Column A was kept constant by using Column B as an overfl ow system for measuring the 20% index. The temperature of the solution in the columns was maintained at 30°C using water circulating at a constant temperature through a jacket surrounding the columns. Fixing a single wet hair fi ber in the experimental apparatus. First, the standard position for the test was determined by placing a 120.0-mm-high metal block on the lower jaw and adjusting the position of the cross head such that the distance between the edge of the upper and lower jaws could be set exactly at 120.0 mm, as shown in Fig- ure 1. Second, one end of the hair fi ber was connected to a 100-g load cell using the upper jaw, and the other end was passed through the fi ne path of the silicon stopper and connected to a small 0.5-g weight in order to straighten the fi ber. After shutting the lower jaw using 3.0 kg/cm2 of air pressure and closing the three-way stopcock, Column A was fi lled with water. The straight hair fi ber was loosened in the water for 5 min. The water was then discharged, the lower jaw opened, and the wet fi ber was allowed to straighten. Subsequently, the lower jaw was shut and, if the fi ber loosened, the lower jaw was opened and the cross head was moved to a slightly higher position, whereupon the lower jaw was again shut at this position and the cross head was moved down such that the wet fi ber could be fi xed at the standard position without slack. By repeating this procedure through trial and error, the standard conditions for a 120.0- mm–long fi ber tensioned without slack in water with zero strain and stress at the stan- dard position was satisfi ed. Treatment procedure as illustrated in Figure 2. Step 1: Extension. The tensile tester was programmed to extend a single hair fi ber by 1.8 mm (1.5% of the original length) at a rate of 5.0 mm/min in water (1.5% extension) and re- turn to its original position. The extension was recorded at 200 mm/min on recording paper to confi rm the accuracy of the extended length. The value “Fo” measured here was regarded as an index of the Young’s modulus of the fi ber before permanent treatment. Step 2: Reduction. While retaining the strain, the water was discharged by opening the stopcock, and after the stopcock was closed again, a given waving lotion was im- mediately poured into the mouth of the column. Relaxation began at the point la- beled “R” in Figure 2, and the stress gradually decayed (recording speed: 10 mm/min). At a reduction time t (min), the waving lotion was discharged. The value Ft measured here was the apparent residual stress due to reduction and included the swelling stress.

JOURNAL OF COSMETIC SCIENCE 36 Step 3: Rinse. After the waving lotion was discharged, the column was repeatedly fi lled with water and discharged fi ve times, following which the fi ber was immersed in water for 10 min (recording speed: 2 mm/min). Step 4: Reoxidation. The neutralizer was poured into the column, and the fi ber was im- mersed for 15 min (recording speed: 2 mm/min). Step 5: Rinse. The neutralizer was discharged and the reoxidized fi ber was rinsed and im- mersed in water for 5 min (recording speed: 2 mm/min). Step 6: Measurement of the set length. The strain reduced to zero (i.e., the original posi- tion), and the treated fi ber was loosened in water. After marking the starting point (A) on the recording paper, recording speed was set to that used in Step 1 (200 mm/min) and the fi ber was extended again by 1.5% under the same conditions as those described in Step 1. The set length (loosened length) was extended in the absence of stress until point B was reached (i.e., in the range from A to B over an extension length ℓ). The stress appeared at point B and increased until point C was reached, which corresponded to a 1.5% exten- sion relative to the original length [i.e., in the range from A to C, over an extension of length (ℓ)]. The values for ℓ and ℓ measured in this way provided the observed set values Sℓ(ext) (%) for the extensional setting experiment as follows: Sℓ (ext) = ℓ ∕ ℓ × 100 (%), (1) where ℓ is the observed set length and l is the observed extended length. Step 7: Extension. The water was discharged, the lower jaw opened, and the cross head returned to the original position. The treated fi ber was then fi xed at the standard length in water under the same conditions as those used in Step 1 (recording speed: 200 mm/ min), and “f” was measured as an index of the Young’s modulus after treatment. Graph of the reduction progress versus time (Pa/t curve). The data required for establishing the Pa/t curves were obtained independently of the above results using only Steps 1 and 2 and omit- ting all subsequent procedures (Steps 3–7). These measurements were repeated six times us- ing six different single fi bers. The relaxation curve obtained in Step 2 was converted to the apparent progress of reduction, Pa (%), of the hair fi ber with respect to time as follows: Pa = {1 - (Ft ∕ Fo)} × 100 (%), (2) where Ft is the residual stress at t min during reduction (see Step 2) and Fo is the index of Young’s modulus before reduction. Note that the measured stress includes swelling due to the waving lotion, and thus the value for Pa calculated using equation (2) is re- ferred to as the apparent progress of reduction. Ft was measured from the height of the relaxation curve once every minute using a slide caliper. The values for Fo and Ft at each time obtained for the six different hair fi bers were, respectively, averaged, and the mean values were then substituted into equation 2. The calculated average Pa values were then plotted versus time to generate “Pa/t curves,” which were used to characterize the different waving lotions. BENDING SET EXPERIMENT Wortmann determined the bending set by winding hairs as loops on a cylindrical roller and cutting the loops and measuring the fi ber set by observing how much loop initial