Naphthol AS Red
PR9
Alternate Names
Naphthol AS-OL
Permanent Red FRLL
Permanent Carmine
Naphthol Red FRLL
Pigment Description
Naphthol AS Red is one of several napthols with similar names. We were surprised to find PR9 in oil paints currently available on the market - especially because these are primarily found in Cadmium Red imitations, and their lightfastness is not that good. This pigment has only moderate lightfastness- it is given an ASTM II in oil but depending on the paintmaker's pigment supplier, it may only get 5's in tints on the Blue wool scale. In watercolor, Bruce MacEvoy calls it very fugitive, and notes it is ASTM III in watercolor. However, his tests showed even worse performance- something like IV. We primarily noticed this pigment in student lines, and to make matters worse the PR9 was sometimes found alongside other pigments that also performed poorly.
Once again, Monona Rossol's writing raises awareness about potential serious health issues that could arise with this pigment, as it may metabolize to a carcinogen, so please consult her writing for more.
Resources
PR9 pigment data from David G. Myers, The Color of Art Pigment Database, Artiscreation.com
Information about PR9 from Bruce MacEvoy, Handprint Guide to Watercolors, General information about this class of pigments from Handprint,
Rossol, Monona. The Artist's Complete Health and Safety Guide. New York, NY : Allworth Press, 2001. The book is rather dated, updated information is available from her website.
Stats
Lightfastness
Good but may Vary by Medium
Shows slight fading in tints in indoor exposure tests, so could perhaps considered good but not excellent. Not lightfast enough for exterior applications. May range from ASTM I to III, which is too low in our opinion, depending on medium. Lightfastness is ASTM III in watercolor. Refer to Artiscreation for details.
Transparency
Semi-Transparent
Some describe it as semi-opaque, but it seems to be a bit closer to the semi-transparent side
Toxicity
Lower Concern
Low concern, source artiscreation.com. Out of caution, treat all pigments and paints with studio safety protocols.
Chemical Name
Monoazo, 3-hydroxy-2-naphthanilide, AS-OL
C₂₄H₁₇Cl₂N₃O₃
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