Fig. 3. Photographical images (a) and lightness (b) of uncoated and PDA coated hair obtained at different reaction times, in comparison with another hair sample dyed with a commercial permanent black hair dye. UV transmittance (c) of uncoated and PDA coated hair obtained at different reaction times. Photos of PDA coated hair after 30 min deposition with different concentrations of (d) SP and (e) DA. The light-ness of PDA coated hair obtained using different concentrations of (f) SP and (g) DA, determined with a precision colorimeter.