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Naphthol AS-TR

PR7

Alternate Names

Permanent Red F4RH

Permanent Carmine

Naphthol Red F4RH

Pigment Description

This color is probably not sufficiently lightfast for use in artist materials. It makes it onto several of the "not suitable" lists, namely for watercolor and gouache. It is somewhat surprising to see the ASTM I listing for oils. Naphthols in general have problems with fading in tints.

Resources

PR7 pigment data from David G. Myers, The Color of Art Pigment Database, Artiscreation.com

General information about this class of pigments from Handprint

Stats

Lightfastness

Good but not enough data

Low data available, may vary according to medium. Not lightfast enough for outdoor use, but some tests reported in the 1980s NPIRI report slight fading of tints in indoor tests as well. Thought to be ASTM I in Oil and Acrylic, but ASTM III in watercolor.

Transparency

Semi-Opaque

Toxicity

Lower Concern

Low information available, but artiscreation.com has a toxicity rating. Treat all pigments and paints with studio safety protocols.

Tinting

Strong

Chemical Name

monoazo, 3-hydroxy-2-naphthanilide, AS-TR

C₂₅H₁₉Cl₂N₃O₂

with PR7 (Naphthol AS-TR)

No single-pigment Oil found with PR7

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