Chapter 15 517 there appears to be a presumption that dye molecules are similarly extracted. However, permanent dye molecules reside within the hair and not at the surface, so these two processes are vastly different. Moreover, our studies refute this presumption. Figure 17 shows color fade results (see Chapter 9 for a description of the L,a,b color measurement approach) for dyed hair tresses that were subsequently washed with a full-strength shampoo, a half-strength shampoo, and a water control. Results show all three treatments giving rise to comparable levels of color fade, and it must therefore be concluded that shampoos do not induce any additional color fade beyond that of water alone. Moreover, discussions with a number of colleagues throughout the industry have echoed these findings. Figure 16. Rinse water from washing permanently dyed hair Figure 17. Color fade in permanently dyed hair as a function of washing with shampoos and a water control