Gurney Journey

Is the pigment called opera rose lightfast or fugitive? I had always heard it was extremely fugitive, but experts don't agree. 

Opera rose is a quinacridone pigment defined as PR122. According to the authoritative website Handprint, it's very reliable. In fact Handprint rates it as a "Top 40" pigment. They say: "after 800+ hours of sunlight exposure, the samples show no fading or discoloration."

Here's how they explain it:

"Quinacridone magenta PR122 is a lightfast, semitransparent, staining, dark valued, intense violet red pigment, offered by more than 20 pigment manufacturers worldwide. 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 of the nine paint brands listed above, which show color variations that suggest several different pigment particle sizes or pigment suppliers, revealed very little or no color degradation, after 800+ hours of direct sunlight exposure, in both heavy and diluted applications. This puts the pigment solidly in the "excellent" (I) category (BWS 7+)."

"For context, compare these samples to naphthol red (PR170), a pigment with a well established "very good (II)" rating, or with quinacridone rose (PV19), which is considered to have "excellent (I)" lightfastness. This is such a glaring discrepancy that the ASTM test must be flawed or unrepresentative in some way. Because Michael Wilcox relies on the ASTM documents for his pigment ratings, he has been critical of this pigment without any corroborating evidence of its fallability. I suggest you do your own lightfastness test on PR122 paints until a consensus emerges, but at present I see absolutely no reason to avoid this splendid pigment." 

Organic / Inorganic

--The Theory and Practice of Water Colour Painting: Elucidated in a Series of Letters

—Jules Breton, The Life of an Artist: An Autobiography, 1890

The tube color is called the mass tone (or masstone), and the color when thinned down is called the undertone.

For example, what inspired the color treatment on this sketch was the strange behavior of Azo green watercolor. It has a dull olive-green mass tone but the undertone is a rather strong yellow.

Scientists at Purdue University have developed a white pigment that they say is significantly whiter than existing pigments. A surface looks white because it reflects back a diffuse version of most of the the light hitting it. 

This new pigment reflects back up to 98% of the sunlight, while commercially available white pigments only reflect back between 80 and 90 percent.

 

Professor Xiulin Ruan with a sample of his "ultra-white" paint, courtesy BBC and Purdue

According to the BBC:

"The new paint contains a compound called barium sulfate, which is also used to make photo paper and cosmetics. 'We used a very high concentration of the compound particles,' explained Prof Ruan. 'And we use lots of different sizes of particles, because sunlight has different colours at the different wavelength.' How much each particle scatters light depends on its size, 'so we deliberately used different particle sizes to scatter each wavelength.'"

Here's a great exercise to try: paint a snow scene with just ultramarine blue and burnt sienna, plus white gouache.  (Link to YouTube video)