EFFECT OF DYEING AND HEAT ON HAIR COLOR 441 (a) 12 10, _ _ 1 o o 12 [] m m [] & A I I I Dyeing times lO (b) o o ½D 2- [] /x ß ß A o o o o i ! ! i i i 0 1 2 3 4 5 6 Shampooing times Figure 2. Average total color difference parameter (DE*) values measured in six virgin brown hair tresses previously cleansed with ethyl ether. (a): Hair samples were dyed three times with three long-lasting and three tone-up dying formulations of black, red, and blond colors. (b): The dyed tresses were submitted to six sequential shampooing cycles. Reference values: color parameters measured in the same tress before dyeing. Symbols: (m) long-lasting black, ([•) tone-up black, (') long-lasting red, (/•) tone-up red, (0) long-lasting blond, and (O) tone-up blond.

442 JOURNAL OF COSMETIC SCIENCE Table I Color Difference Parameters of Brown Hair Samples Exposed to Hot Plate at 172øC (average temperature) Sample 1 Sample 2 Exposure time (min) DL* Da* Db* DE* DL* Da* Db* DE* 1 -2.56 -0.75 -1.01 2.86 -1.41 -0.27 -0.35 1.48 2 -4.71 -0.82 -1.10 4.91 -4.25 -0.34 -0.26 4.28 3 -5.26 -0.58 -0.67 5.34 -4.57 -0.29 -0.07 4.57 4 -5.08 -0.71 -0.68 5.18 -4.89 -0.20 -0.17 4.90 5 -5.25 -0.39 -0.60 5.30 -4.21 -0.20 -0.37 4.23 6 -4.82 -0.33 -0.38 4.86 -3.69 -0.38 -0.41 3.75 7 -5.18 -0.79 -1.20 5.38 -5.20 -0.32 -0.51 5.24 8 -5.50 -0.68 -1.16 5.66 -4.23 -0.31 -0.44 4.28 9 -5.48 -0.38 -0.64 5.54 -4.14 -0.09 -0.38 4.16 10 -5.37 -0.50 -0.90 5.47 -4.80 -0.35 -0.56 4.85 Sample 1 rej•rence values: L* = 29.72, a* = 2.26, b* = 2.35. Sample 2 re•rence values: L* = 28.62, a* = 2.06, b* = 2.08. Table II Color Difference Parameters of Brown Hair Samples Treated With Silicone and Exposed to Hot Plate at 172øC (average temperature) Sample 1 Sample 2 Exposure time (min) DL* Da* Db* DE* DL* Da* Db* DE* 1 0.07 -0.48 -0.44 0.92 1.42 -0.05 -0.17 1.47 2 0.80 -0.32 0.07 0.90 1.98 -0.08 -0.14 2.00 3 0.59 -0.60 -0.72 1.25 0.80 -0.21 -0.90 0.88 4 0.90 -0.64 -0.68 1.35 1.54 -0.14 -0.23 0.52 5 1.02 -0.43 -0.49 1.21 0.86 0.03 -0.06 0.99 6 0.74 -0.52 -0.67 1.21 0.97 0.01 0.05 1.00 7 0.64 -0.50 -0.27 1.01 1.01 -0.05 0.08 1.13 8 0.55 -0.37 -0.40 0.85 1.05 0.04 0.17 1.09 9 0.34 -0.50 -0.63 0.92 0.99 0.22 0.41 1.15 10 0.47 -0.33 -0.40 0.77 0.76 -0.10 0.04 0.83 Sample 3 rej•rence values: L* = 21.77, a* = 2.44, b* = 2.62. Sample 4 rej•rence values: L* = 21.51, a* = 1.76, b* = 1.85. RESULTS AND DISCUSSION EFFECT OF DYEING AND SHAMPOOING CYCLES The dyeing experiments were done to quantify color saturation in hair using commercial dyeing products and processes. Secondly, consecutive shampooing cycles of dyed hair samples were performed to observe dye persistence in hair. Permanent dyeing using long-lasting and tone-up formulations were applied to the virgin hair cleansed or not cleansed with ethyl ether. Figures 1 and 2 show the color difference parameter (DE*) obtained after dyeing and subsequent shampooing of hair samples not extracted with ether and of hair previously