Art Spectrum Artists' Gouache - Crimson, 22.5 ml

Pigment Information

This color contains the following pigments:

PR170-Naphthol Red

PR81:1-Rhodamine 6G

Pigment Name

PR170-Naphthol Red

Pigment Type

organic, naphthol AS

Chemical Formula

C26H22N4O4

Properties

Pigment PR170 is a bright deep red with bluish undertones. It has an average drying time. It has two crystaline forms that differ significantly in opacity. The more transparent form (F5RK) tends to be more bluish and is less lightfast.

Permanence

The lightfastness and weatherfastness of Pigment PR170 varies, depending on the application and the crystaline form. The opaque form (F3RK) has very good lightfastness, and is more weather resistant. The transparent form (F5RK) has lightfastness that is considered acceptable in pure applications, but it fades more in tints. Neither form is considered suitable for exterior use.

History

Naphthol pigments are actually dyes that are "laked" to form pigments. First developed by the German chemical company Hoechst A.G. before World War I, their use in artist paints began in the 1920s. Pigment Red PR170 is a Naphthol AS pigment, chemically related to the diarylide yellow pigments. The Naphthol AS pigments comprise a range of reds. They are used in plastics, textiles, and printing inks.

Pigment Name

PR81:1-Rhodamine 6G

Pigment Type

organic, fluorone dye

Chemical Formula

C28H31N2O3Cl

Properties

Rhodamine 6G is a staining reddish-yellow pigment that has fluorescent properties. It is extremely soluble in both water and alcohol. Fluorescent molecules absorb light at one wavelength and emit light at a longer wavelength.

Permanence

Rhodamine 6G, like all fluorescent dyes, is not considered permanent, however it is reported  to have high stability for a fluorone dye.

History

Rhodamine dyes are often used for microscopy in the biological sciences.