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 European Commission banned titanium dioxide as a food additive in the EU in 2022 after the European Food Safety Authority (EFSA) conducted an updated safety assessment of E171 and concluded the panel could not eliminate concerns about its genotoxicity.
One of the primary advantages of lithopone is its excellent thermal stability. It performs well under high-temperature conditions, which is essential for paints that will be exposed to extreme weather. Lithopone’s resistance to UV radiation helps maintain the brightness and color integrity of paints, making it a preferred choice for outdoor applications. As a result, many suppliers are focusing on providing lithopone that meets the specific needs of manufacturers in the architectural, automotive, and industrial paint sectors.