2.4.1. Colorimetry

For measuring color, a portable spectrophotometer colorimetry Data Color International was used. Its measuring head's optical system uses diffuse illumination from a pulsed Xenon arc lamp over the 8mm-diameter measuring area, with 0º viewing angle geometry. Color coordinates were calculated defining the D65 illuminant and the 10º observer. The calibration was performed with a white bright standard plate and a total black standard. Color, as perceived by the human eye, may be represented in a three-dimensional system. The color data are presented in the CIE-Lab system. In the Lab cartesian system, L\*, relative brightness, is represented by the z-axis. Variations in relative brightness range from white (L\* = 100) to black (L\* = 0). The (a\*, b\*) pair represents the hue of the object. The red/green y-axis plots a\* ranging from negative values (green) to positive (red). The yellow/blue x-axis reports b\* going from negative (blue) to positive numbers (yellow).
