EFFECT OF CURLING IRONS 235 (a) 3.50E+06 3.00E+06 n m 2.50E+06 ._.•. 2.00E+06 • 1.50E+06 • 1.00E+06 5.00E+05 O.00E+00 unexposed: 145o/1433 = 0.97 30 min: 145o/1433 =1.02 350 400 450 500 550 Wavelength (nm) (b) 1.20E+07 D. 8.00E+06 .•' 6.00E+06 • 4.00E+06 2.00E+06 O.00E+00 325 unexposed unexposed: 145o/1433 = 0.95 /' ....................................... .,•, 30 min: 145o/14aa = 0.95 ......... '• 30 min ...... • ...... 375 425 475 525 575 Wavelength (nm) 1.20E+07 unexposed unexposed: 145o/1433 = 0.95 1.00E+07 ....................................... 30 min: 1450/1433 = 0.95 D- 8.00E+06 (c) m ,. ........... 30 min ................. • 4.00E+06 2.00E+06 O.00E+00 .... 355 405 455 505 555 Wavelength (nm) Figure 6. The emission spectra of bleached hair, at excitation wavelengths of 290 nm (a), 320 nm (b), and 350 nm (c), before thermal exposure and after 30 min of treatment. Thermal treatment was administered at 164øC. In this reaction, higher-molecular-weight residues of melanin decomposition, which cannot be removed by rinsing due to their large size, undergo polycondensation, result- ing in the reformation of the melanin pigment. In the case of Piedmont and white hair, changes in lightness (AL) are accompanied by a significant variation in the parameters

236 JOURNAL OF COSMETIC SCIENCE (a) 1.06E+06 9.06E+05 8.06E+05 7.00E+05 6.00E+05 5.06E+05 4.06E+05 3.06E+05 2.06E+05 1.06E+05 0.06E+06 306 unexposed unexposed: 145o/14,s = 0.77 ß : ---- , , •0 406 450 506 Wavelength (nm) (b) 1.20E+06 1.06E+06 Q- 8.06E+05 ._•- 6.06E+05 • 4.06E+05 2.06E+05 0.06E+06 330 30 mj,• ............................. unexposed: 14sdl4,s = 0.74 '• •:" '••.......,.. 30min: 1450/14,5=0.80 , i i i i 380 430 480 530 580 Wavelength (nm) 2.50E+06 (c) ß --, 1.50E+06 • 1.OOE+06 "5.06E+05 0.060E+06 30 min ,• .................. --,-....... unexposed: 14so/1415 = 0.81 ,,,= ............................... 30 min: 1450/1415 = 0.88 ,,,," '•,,•,,, 360 41 0 460 51 0 560 Wavelength (nm) Figure 7. The emission spectra of light-brown Caucasian hair, at excitation wavelengths of 290 nm (a), 320 nm (b), and 350 nm (c), before thermal exposure and after 30 min of treatment. Thermal treatment was administered at 164øC. Aa and Ab, which leads to a large change in chromaticity (AC). This is also reflected by large increases in the yellowness indices for these two types of hair, as well as for bleached hair. Pigmented hair, on the other hand, experienced small differences in yellowness.