Pyrazolone Orange
PO34
Alternate Names
Dizazopyrazolone Orange
Pyrazalone orange RL-70
Diarylide Orange RL01
Diarylide Orange RL70
Fast Orange F2G
Pigment Description
There may be several subvariants of this pigment, which are mentioned in this article, which mentions a "standard grade" as well as a redder kind that is more opaque. We've also encountered subtypes with differing lightfastness such as PO34 RL01 (Lightfastness V, very poor) and RL70, which has better but still bad lightfastness at ASTM III. For artistic work, the lightfastness of this orange is pretty terrible in tints (possibly as low as 4 on the BWS). For that reason alone we don’t feel it is advisable to use it. However there are other reasons for avoiding its use.
According to Monona Rossol's work, this is a very concerning color from a health standpoint and will likely metabolize into a carcinogen. We advise all artists to research benzidine in artist pigments for toxicity. Surprisingly this color is used by at least three major paintmakers in oil as single-pigment color.
Depending on the supplier the pigment ranges from inadequate lightfastness to poor, and even in the better ratings it's not that good. It's also found in blends by about six paintmakers and sometimes it is paired with other pigments that also have lightfastness issues. Artiscreation notes that Lightfastness may be slightly improved in redder versions. However the performance is reported to be not very good. Unfortunately several paintmakers use this color in their paints.
Resources
PO34 pigment data from David G. Myers, The Color of Art Pigment Database, Artiscreation.com
Information about PO34 from Bruce MacEvoy, Handprint Guide to Watercolors,
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
Poor
Even in masstone this pigment fades down to a moderate rating. In watercolors, Bruce MacEvoy found its lightfastness to be poor. Due to its serious lightfastness issues, he described the pigment as \”irrelevant". An old version of the 1980s NPIRI echos these findings and reported “appreciable” change in both masstone and tints in outdoor exposures, while even indoor exposures showed slight change in masstone and appreciable fading in tints.
Transparency
Semi-Opaque, Opaque
Most paints formulated with this color are semi-opaque, however there are some opaque versions. The NPIRI mentions that the opaque versions are similar in color to PR104.
Toxicity
Previously thought to be in the category of Low Concern, new research suggests this may metabolize to a carcinogen, may also contain toxic impurities.
May metabolize to a carcinogen. Refer to Monona Rossol's research available upon request here for more information. In the 1980s the NPIRI noted it may contain PCBs, a toxic impurity.
Chemical Name
Disazo, diarylide / pyrazolone
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