2.3.4. Light transmission and transparency
The barrier properties of films against ultraviolet (UV) and visible light were measured at selected wavelength between 200 and 800 nm using the method described by Fang, Tung, Britt, Yada, and Dalgleish (2002). Film portions of 10 _ 40 mmwere placed into the test cell of a UV-1650 spectrophotometer (Model PC, Shimadzu, Kyoto, Japan), using an empty test cell as the reference. The measurement was done in triplicate and the average of three spectra was calculated. The transparency of the films was calculated by the following equation: