Naphthol Scarlet Lake, Naphthol AS

PR188

Alternate Names

Naphthol AS BON Arylamide

PR188HF3S

Pigment Description

There may be two varieties of this pigment, as we have encountered lightfastness ratings for a regular PR188 and another one called PR188H3FS. The regular version seems to be slightly more lightfast.

In regard to regular PR188, the term Naphthol AS gets applied to a handful of pigments, so this may refer to a really fabulous color which used to be quite popular in some smashing convenience pinks, which did not contain pigment data but simply read naphthol as without further information. If PR188 is the napthol AS we've used, it is truly gorgeous, and we were loathe to retire it from our palettes. There are reports that it may fade in tints. Some sources show only moderate lightfastness in tints (BWS 6), which is too low for our purposes.

PR188H3FS Is listed as Naphthol Red AS, and it has a separate lightfastness in watercolor of ASTM III.

Resources

PR188 pigment data from David G. Myers, The Color of Art Pigment Database, Artiscreation.com

Information about PR188 from Bruce MacEvoy, Handprint Guide to Watercolors, General information about this class of pigments from Handprint,

Stats

Lightfastness

Rated as Excellent in Oils and Acrylic but Very Good in Watercolor

Lightfastness may only be moderate in tints. Also Artiscreation reports some darkening and/or fading. The ASTM II in watercolor is of interest. Bruce MacEvoy found some brands which were slightly better than others, however he recommends more lightfast pigments instead.

Transparency

Varies

Can vary anywhere from transparent to opaque formulations in oil, Semi-Transparent in watercolor

Toxicity

Hazard, Use more caution

Artiscreation rates this as a B, so there are precautions that are needed. Always consult the SDS as well as third party expert sources. In general, treat all pigments and paints with studio safety protocols.

Dry Time

Varies

Some brands make oils that dry in 2 days while others list this as moderate or even as Very Slow. The wide range makes one suspect the use of driers in the faster varieties.

Particle Size

Fine

Chemical Name

Monoazo, 3-hydroxy-2-naphthanilide, AS

Dry Pigments listing PR188

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