PR 3 – toluidine red

Created in 1904, became popular in the 70′ because it was cheap but not stable. It was used in all industrial and artistic applications

Manufacturer/ product code:  Kremer / 23950
Chemical Description:  beta naphthol toluidine
Color: red
Color Index: PR 3
Date:  from 1904

PR 3 – Toluidine Red is a synthetic organic pigment belonging to the monoazo family, historically significant as one of the earliest widely used bright red pigments of the 20th century. Introduced in the early 1900s, PR 3 became popular for its strong, warm red hue with orange undertones, relatively high tinting strength, and ease of manufacture, making it a staple in printing inks, paints, and early artists’ materials.

Chemically, Toluidine Red is based on an azo (-N=N-) linkage connecting aromatic rings derived from toluidine compounds. While this structure is responsible for its vivid coloration, it also results in moderate to poor lightfastness compared to modern high-performance organic pigments. Prolonged exposure to light, particularly UV radiation, can cause fading and loss of chromatic intensity, a characteristic well documented in both industrial applications and historical artworks.

In practical use, PR 3 typically exhibits good opacity and strong coloring power, producing bright scarlet to vermilion-like reds. It mixes readily with yellows to form intense oranges and with whites to yield clean pinks, though these tints are especially vulnerable to fading. Because of its fugitive nature, PR 3 has largely been replaced in contemporary formulations by more stable alternatives such as pyrrole, quinacridone, or perylene reds.

From a conservation and analytical standpoint, Toluidine Red is an important pigment marker for dating and material identification in 20th-century objects. Its presence often indicates industrial or decorative paints rather than fine artists’ materials intended for long-term permanence.