Colorimetry
As shown above (Fig. 5), irradiation of celluloid leads to the
formation of photoproducts that absorb light in the visible domain.
This absorption can be correlated to colour changes of the irradiated
samples. This evolution of the colour can be characterized
using a CieLAB colorimeter. Fig. 11 shows the discolouration
observed after 200 h of exposure of a celluloid sample and Table 4
gives the L*, a*, b* parameters before and after 200 h of irradiation.