JOURNAL OF COSMETIC SCIENCE 48 HAIR DAMAGE Hair damage after permanent treatment, such as changes in appearance, roughness, gloss, and stiffness, are evaluated by hairdressers using a feeling test. Such delicate Figure 8. Relationship between the extensional set and the bending set. (A) Plot of Sℓ(bend) vs. Sℓ(ext) using the same hair under the various conditions shown in Table III. ( )A–S (reduction time 9.5–11 min) (–) A–N ( 9–15 min) ( (+) C–W ( 3–15 min).B–S ( 5 min) ( )B–N (16 min) ( ) B–N: (5 min) (▲) B–S (16 min) ( )B–S (5 min) Correlation: y = 0.787X + 18.20, r = 0.974. Note: In short reduction time (5 min), ( )B–N ( ) B–S, in long reduction time (16 min) ( )B–N (▲)B–S. This behavior is similar to that observed for the Pa/t curves of B–N and B–S as shown in Figure 5(A). (B) Difference in the reduction rates in the exterior and interior of wound hair using TGA–NH4 is determined on the basis of the formation of S–Hg–S bonds. The exterior reduction is clearly greater (see text). Table IV Wave Effi cacy and Setting at 5 Min on Pa/t Curve Wave lotion Pa at 5 min(%) Calc.Sℓ(ext)(%)a Wave effi cacy(%)b Average (SD) Average Sℓ Average (±) A–S 75 (4.2) 75.2 58.2 (±2.5) A–N 31.8 (5.6) 25.2 49.7 (±2.5) A–W 26.2 (6.1) 18.7 45.7 ± 2.5 B–S 51.5 (9.1) 48.0 59.2 (±2.5) B–N 61 (11.3) 59.0 61.2 (±2.5) B–W 24.4 (1.5) 16.6 48.8 (±2.5) C–S 47.5 (9.5) 43.4 51.5 (±2.5) C–N 21.2 (3.7) 12.9 45.5 (±2.5) C–W 17.3 (1.9) 8.4 42.5 (±2.5) aCalculated using the graph in Figure 9(C). bMeasured by a hairdresser.

PRACTICAL SELECTING METHOD OF WAVE LOTION FOR HAIR DRESSER 49 characteristics cannot be determined using mechanical tests. However, if damage is re- stricted to a decrease in the stiffness or the Young’s modulus after treatment, damage evaluation should be possible by measuring Ero (f/Fo), as previously discussed. Ero is directly related to the set value as shown in equation (5) and it should be empha- sized that in the present study Ero did not simply decrease when Pa increased but abruptly decreased when Pa was approximately 80%, regardless of the wave lotion and the reduc- tion time, as shown in Figure 10(A), which was drawn by plotting the values for Ero vs. the values for Pa listed in Table II. However, these plots with steep declines were obtained only at long reduction times. In order to confi rm this important behavior, therefore, Ero was measured at various Pa values for the A–S, A–N, and C–W lotions as representative wave lotions. As can be seen in Figure 10(B), the abrupt decrease in Ero when Pa was ~80% was observed for the three wave lotions. It should be noted that the existence of this critical point (Pa = 80%) refl ects the point at which hair damage occurs. In addition, it can be imagined that this behavior relates with the characteristic kinetics of TGA-NH4 Table V 20% Index of Virgin Hair in Water at 30°C Japanese senior high school girlsa) Japanese in beauty parlorb Chinesec German ladiesd (45) Parlor-A(8) Parlor-B(7) (6) (8) 61.2 61.0 61.7 61.5 62.2 62.4 62.4 60.7 60.2 62.1 61.1 61.4 61.7 59.1 61.0 62.5 61.9 61.1 61.3 59.6 60.7 62.5 60.9 62.3 61.6 61.7 61.1 61.4 60.4 59.9 60.5 61.9 62.0 61.3 61.2 62.0 62.8 63.4 61.7 61.1 60.2 60.5 60.4 60.9 62.2 61.4 62.5 61.6 61.8 62.0 62.6 62.2 62.5 62.6 61.8 61.7 62.6 62.6 61.7 62.1 61.3 61.2 62.1 62.9 61.5 61.8 61.4 61.9 60.2 62.5 62.1 61.2 61.9 Average of 20% index (%) 61.7 61.6 61.7 61.1 61.0 The total number of virgin hairs, 74 Mean ± SD = 61.6 ±0.8(SD) aDonated by students at Tokyo Metropolitan Toyama High School, Tokyo, Japan. bFrom Parlor A (the beauty parlor “Boy” in Tokyo) or Parlor B (the beauty parlor “ADOMI” in Hachinohe). cPicked up at random from Chinese hair tissue purchased from hair supplier (Deaulax Co. Ltd., Saitama, Japan). dDonated by Dr. S. Roeper in Hamburg, Germany.