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zinc sulfide content, %

Although barium sulfate is almost completely inert, zinc sulfide degrades upon exposure to UV light, leading to darkening of the pigment. The severity of this UV reaction is dependent on a combination of two factors; how much zinc sulfide makes up the pigments formulation, and its total accumulated UV exposure. Depending on these factors the pigment itself can vary in shade over time, ranging from pure white all the way to grey or even black. To suppress this effect, a dopant may be used, such as a small amount of cobalt salts, which would be added to the formulation. This process creates cobalt-doped zinc sulfide. The cobalt salts help to stabilize zinc sulfide so it will not have as severe a reaction to UV exposure.

The availability of other white pigments poses a major challenge for the Lithopone market during the forecast period. Other alternatives to Lithopone include Zinc White, Titanium Dioxide, Calcium Carbonate, Blanc Fixe, and Barytes. The use of TiO2 has reduced the commercial significance of the Lithopone in the pigments industry.