This article discusses the discovery of phosphorescent lithopone on watercolor drawings by American artist John La Farge dated between 1890 and 1905 and the history of lithopone in the pigment industry in the late 19th and early 20th centuries. Despite having many desirable qualities for use in white watercolor or oil paints, the development of lithopone as an artists’ pigment was hampered by its tendency to darken in sunlight. Its availability to, and adoption by, artists remain unclear, as colormen's trade catalogs were generally not explicit in describing white pigments as containing lithopone. Further, lithopone may be mistaken for lead white during visual examination and its short-lived phosphorescence can be easily missed by the uninformed observer. Phosphorescent lithopone has been documented on only one other work-to-date: a watercolor by Van Gogh. In addition to the history of lithopone's manufacture, the article details the mechanism for its phosphorescence and its identification aided by Raman spectroscopy and spectrofluorimetry.
Titanium dioxide holds exceptional significance as a white pigment due to its superior scattering capabilities, remarkable chemical stability, and non-toxic nature. Among all white pigments, it surpasses others in terms of its ability to scatter light effectively. Consequently, titanium dioxide stands as the most significant inorganic pigment, accounting for the highest quantity in usage. The majority part of the global production of ilmenite and rutile is dedicated to the production of TiO2 pigments. The remaining portion is utilized for the manufacturing of titanium metal and in the production of welding electrodes.
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