PR 112 – naphthol red AS-D

Widely used pigments in industry and arts

Manufacturer/ product code:  Kremer / 55300
Chemical Description: naphthol
Color: red
Color Index: PR 112
Date:  1912

PR 112 – Naphthol Red AS-D is a synthetic organic pigment belonging to the naphthol AS azo pigments, a class introduced in the early 20th century to provide strong, economical reds with good color strength and a wide tonal range. PR 112 is characterized by a deep, slightly bluish red that can shift toward crimson in mass tone while retaining clarity in tints.

Chemically, PR 112 is a monoazo pigment, formed by coupling a diazo component with a naphthol AS derivative. This structure gives the pigment its high tinting strength and relatively good opacity compared to many other organic reds. However, like most naphthol AS pigments, its molecular framework is less stable than modern high-performance pigments such as quinacridones or pyrroles.

In artistic and industrial use, PR 112 has been appreciated for its clean masstone and vivid undertones, making it suitable for printing inks, plastics, and coatings, as well as for student- and mid-grade artists’ paints. It mixes readily with yellows to produce strong oranges and with blues to create deep violets, though mixtures can darken if overworked.

From a durability standpoint, PR 112 typically shows moderate lightfastness (often ASTM II–III, depending on formulation and binder). Under prolonged light exposure, especially in thin films or pale tints, some fading or dulling may occur. For this reason, it is generally not recommended for critical conservation work or artworks intended for maximum longevity, where more stable alternatives are preferred.

In conservation science and technical examination, Naphthol Red AS-D is identifiable by its characteristic organic spectral features rather than elemental markers, and its presence can help date or contextualize modern paints and coatings.

Overall, PR 112 represents a historically important and widely used red pigment, valued for its color strength and economy, but with known limitations in permanence when compared to newer organic reds.