2.4. Instrumental color
Color measurements for all investigated samples were performed
with Hunter colorimeter (ColorTec PCM, USA) using D65
illuminant in Hunter color space (L⁄, a⁄, and b⁄). Corresponding values
of hue angle (H⁄) and chroma (C⁄) were calculated as
Prior analysis, colorimeter was calibrated by white tile (standard
no. LS-13903) with standard color coordinates L⁄ = 94.65,
a⁄ = 0.82 and b⁄ = 0.83. The L⁄, a⁄ and b⁄ values were obtained
in triplicates and analyzed in Hunter Associates glass sample cup
(m = 25 ± 1 g) that was placed in colorimeter.