Naphthol Red AS
PR170
Alternate Names
Permanent Red
Permanent Carmine
Naphthol Red F5RK-A
Naphthol Red F3RK
PR170 F3RK-70
Napthol Red F5RK
Pigment Description
This is a gorgeous red that made some stunning pinks, but lightfastness can vary widely. There are two PR170 pigments assessed by the ASTM, which are F3RK-70 and F5RK. Their lightfastness may vary across media.
In general, looking at the Blue Wool Scale readings for PR170 (type unspecified) the lightfastness appears moderate (meaning not good enough) lightfastness. Bruce MacEvoy's tests in watercolor suggest to avoid this color. There appear to be at least two forms of this pigment, blue shade and yellow shade, and one is more lightfast than the other. Bruce MacEvoy notes there may be dozens of sub-varieties of this pigment.
May be related to health problems, such as methemoglobinemia, as well as some other things. See Monona Rossol's work for more.
Resources
PR170 pigment data from David G. Myers, The Color of Art Pigment Database, Artiscreation.com
Information about PR170 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 to Moderate
One lightfastness test results from the NPIRI noted a slight fading in tints, even in indoor exposure conditions. This color unfortunately can fall to a moderately poor score in tints (5 on the BWS), which is not great. While the two varieties of this color could be a factor in which ones get poorer scores, we did notice in a pigments and coatings article that PR170 was recommended for "applications requiring less than the ultimate UV resistance," which makes sense.
Transparency
Semi-Transparent, Semi-Opaque
Toxicity
Lower Concern
Treat all pigments and paints with studio safety protocols; may cause methomethemoglobinemia, refer to Monona Rossol's work for details.
Chemical Name
napthol carbamide (F3RK version)
DISCLAIMER: Please note that we are not experts in health and safety and we are not toxicologists, please consult the proper experts. We are not liable for any issues that may arise from the use of our website or its contents. The information contained in this site is provided without warranty or guarantee of any kind. We do not necessarily endorse any other website that are linked from our site. For any important pigment specs, please reference the manufacturer details. If you discover errors or omissions, please reach out through our contact form. Thank you.
