R-996 titanium dioxide, white powder, insoluble in water, non-physiological toxicity, chemically stable, with excellent weather resistance and anti-powdering ability.
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.
As for titanium dioxide, the FDA approved titanium dioxide for use as a food additive in 1966. The last time the agency reviewed the additive’s safety, according to the Guardian, was in 1973.
Faber argued there hasn't been enough change in these federal regulations in the decades following the FDA's approval of titanium dioxide – especially as others increasingly point to potential health consequences.
Less frequently, we ingest E171 through liquids such as salad dressing, dairy products, and some artificially colored drinks. However, since E171 is insoluble, manufacturers must use other stabilizers to keep E171 suspended in liquids as an emulsion; otherwise, it will settle to the bottom.