The effecto f light alone,e xtractedf rom the compositeo f chemical-a nd light-induced
damages howni n the above-mentionetdw o figures,i s depictedi n Figure4 . For comparison,
w e havea lsoi ncludedt he data obtainedf or the undyedh air. The slopeso f the
curvesa rep roportionatlo the rateo f damaget:h e largert he slope,t he lesst he protection.
These data clearly reveal that the permanentc olor is more efficacioust han the demipermanenwt
hen appliedt o unpigmentedfi bers.T his is likely due to the fact that since
the permanent coloring products are left on the hair for 25 minutes, compared to ten
minutes for the demipermanenpt roducts,t hey depositm ore dyes on the hair. This
higher dye deposit, in turn, leads to a higher degree of photoprotection