440 JOURNAL OF COSMETIC SCIENCE (a) ½"5, ILl •4- 02 o 1 ß [] A ß ß o ß ! I Dyeing times (b) _ ß ß [] [] • [] ß ß ß A ß 0 A ß o o 0 ' I I I I 0 2 3 4 • 6 Shampooing times Figure 1. Average total color difference (DE*) values measured in six virgin brown hair tresses. (a): Hair tresses were dyed three sequential 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: (I) long-lasting black, ([•) tone-up black, (A) long-lasting red, (/•) tone-up red, (0) long-lasting blond, and (O) tone-up blond.

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.