More pigments (Re: Why Winsor & Newton?

Katharine Thayer wrote:
>
> Christina Z. Anderson wrote:
> >
> > > Christina Z. Anderson wrote:
> > > Now, Holbein does have one color that no other person makes quite
> > >> the same--Opera. Can't wait to make a gum with that as my magenta of
> > >> choice.
> > Katharine wrote:
> > > Just so you know, one of the pigments in that paint, basic violet 10, is
> > > fugitive. (The other pigment is PR122, quinacridone magenta).
> >
> > Interesting, but Page gives it 3 stars, her highest rating, saying
> > lightfastness is very good. Maybe because the PR122 is lightfast enough to
> > carry the PV10. I wonder exactly what the PV10 contributes to the color.
>
> Actually, that's BV 10...
>
> Well, it comes down to who ya trust, I guess. True, Hilary Page gives it
> a "very good" lightfast rating, but that's one step down from her best
> rating, "excellent." and according to Page, Holbein itself only gives it
> a "moderate" rating. At any rate, whenever there's a discrepancy
> between sources about the lightfastness of something, I always go with
> Bruce MacEvoy (handprint.com) who does extensive and repeated testing of
> all the pigments and who says of this paint, "Holbein opera is a much
> more intense bluish pink hue (chroma of 72), a fascinating and effective
> floral and flamingo color, but marginally lightfast because the basic
> dye rhodamine B (BV10) has been added; it should not be used for
> collectible quality artwork."

Out of curiosity I did some more sleuthing about this paint and about
the BV 10 pigment, hoping to prove myself wrong about it. What's
interesting is that the paint was apparently reformulated at some point;
before that point it was made with PV1 (+PR122) and for some reason they
switched from PV1 to BV 10, or maybe just changed the name of the
pigment, since these pigments are essentially interchangeable. Both
are Rhodamine B and both equally fugitive. One source says of Rhodamine
B, that it is a "brilliant but temporary violet red... Valued by the
printing industry for its strength and brilliance, it is the standard
printing ink, magenta. With a dismal record as far as permanence is
concerned, it is surprising to find it used in an artist's paint." So
it seems like a consensus, except for Hilary Page's anomalous rating of
"very good" in spite of her listing a pigment with the common name of
"holbein opera" as "fugitive" in her pigment listings.

While we're at it, there is also some question about the lightfastness
of the PR122 (quinacridone magenta) that's also in this paint ASTM
rates it at III (fair) but there is considerable dispute about that.
Bruce MacEvoy tested 9 single-pigment paints made from this pigment and
rated all but one of them 7,8 (the two numbers are for tint, masstone)
on an 8-point scale, with 8 being most lightfast. (The one exception was
Sennelier's "quinacridone purple" which was rated at 4,5.) Hilary Page
also rates this pigment better than the ASTM rates it. MacEvoy says this
about the pigment: "The ASTM (in technical report D5067-99) rates the
lightfastness of PR122 in watercolors as "fair" (III, "may be
satisfactory when used full strength or with extra protection from
exposure to light"), but other manufacturer and independent tests rate
it higher. My 2004 lightfastness tests, which included the
representative sampling of paint brands listed above, revealed very
little or no color degradation after 700+ hours of direct sunlight
exposure, in both heavy and diluted applications, putting the pigment
solidly in the "excellent" (I) category (BWS 7+). This is such a glaring
discrepancy that the ASTM test must be flawed or unrepresentative in
some way." --(From
http://www.handprint.com/HP/WCL/waterfs.html)

Given my confidence in Bruce MacEvoy's expertise, I'm inclined to go
with his rating of this pigment and call it lightfast, but he suggests
that people should do their own testing on this pigment "until a
consensus emerges."
Katharine
Received on Wed Jun 1 21:11:16 2005