Naphthol Red AS

PR170

Alternate Names

Permanent Red

Permanent Carmine

Naphthol Red F5RK-A

Naphthol Red F3RK

PR170 F3RK-70

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. There appear to be two forms of this pigment (blue shade and yellow shade), and one is more lightfast than the other.

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

Very Good to Moderate

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

Toxicity

Thought to be in the category of Lower Concern

Treat all pigments and paints with studio safety protocols.

Chemical Name

napthol carbamide (F3RK version)

Dry Pigments listing PR170

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.