"Indanthrone blue, also called indanthrene, is an organic dye made from 2-aminoanthraquinone treated with potassium hydroxide in the presence of a potassium salt. It is a pigment that can be used in the following mediums: acrylic, alkyd, casein, encaustic, fresco, gouache, linseed oil, tempera, pastel, and watercolor painting. It is used to dye unmordanted cotton and as a pigment in quality paints and enamels. As a food dye, it has E number E130, but it is not approved for use in either the United States or the European Union.
It was the first example of the brand "Indanthren" (an acronym for Indigo from anthracene) introduced by BASF in 1901. One coincidental result is that even now, in Japan vat dyes are commonly described as thren(e) dyes (スレン染料), derived from the Japanese transliteration of the brand." - (en.wikipedia.org 07.06.2021)
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