When asked on the Facebook group what choices of violet pigments Virgil would use, he answered: cobalt violet, manganese violet, ultramarine violet, or mixtures of cobalt blue or ultramarine blue and a lightfast purple-red like PV 19 or Mars violet, depending on the desired chroma. Lower chroma violets can be made with red and black plus white.
A Facebook user asked how Virgil would mix an opaque light purple. His answer: “Without adding a white, you won’t be able to get a light purple opaquely, so the only other way would be to apply a transparent purple thinly over a white underlayer. That creates a different optical effect that works better for some things than for others, so it might not be as good an option as adding lead white or ceruse, depending on what you’re trying to do.”
From Natural Pigments’s article, “Color Notes: Ultramarine Violet in Painting“: “Works of art rarely contained the color violet until the Impressionists in the mid-19th century. A study of the color violet has shown it to be present in only 2% to 4% of the artworks created before the early 1860s. It quickly became very popular soon after that date, rising from 36.5% to 47.9%. What explains the steep increase in the use of violet in paintings in the early 1860s? While the introduction of cheap purple and so-called violet pigments in the 1860s made its use more economical for artists, this alone does not explain the trends. According to the same study of the color violet, an increased sensitivity to violet colors due to the continuous evolution of the human visual system offers an alternative explanation. In addition, the contemporary developments in color theory and their adoption by Impressionist painters may almost naturally have led to an increase in the use of violet from 1863 onwards.”
Pigment Number: PR101
Mars violet is a synthetic red iron oxide described as being a subtle, deep bluish-red that makes lavender tints. It is similar to Indian Red and is often called that name or Caput Mortuum (“dead head”).
Here’s a historical note from Natural Pigments: “Mars pigments with a violet hue were first produced by making mars yellow. This compound was then calcined and oxidized to form red shades of iron oxide(III). It is believed that the first pigments offered as mars violet were the natural mineral hematite, which is a red iron oxide earth pigment. This was then calcined and oxidized to produce deeper shades and ground more coarsely than the brighter red shades. Synthetic iron oxide pigments of deep red and violet hues are produced today by the Penniman-Zoph process. When synthetic iron oxide pigments are produced at larger particle sizes, 1–5 microns, they appear closer to violet hues of red. Smaller particle sizes, 0.1 to 0.2 microns, produce brighter yellow shades of red.
The Latin caput mortuum (meaning “dead head,” and variously spelled caput mortum or caput mortem) is the name given to a purple variety of hematite iron oxide pigment. This name may have come from alchemical usage since iron oxide is the oxidized residue (caput mortuum) or rust. It was initially a byproduct of sulfuric acid manufacture during the seventeenth and eighteenth centuries. It was possibly an early form of the copperas process used to manufacture Venetian red and copperas red.”
Virgil uses Natural Pigments version of Mars Violet under the Rublev brand called “Mars Crimson”.
From CAMEO: Synthetically prepared violet color iron oxide pigment. Mars violet is a permanent pigment with good tinting strength and good oil-drying properties.
Pigment Number: PV16
— very high in oil content, transparent
It has a deep rich violet hue, is lightfast, but has poor hiding power.
— asked if the manganese can cause darkening… Virgil responds: I’ve observed no darkening of manganese violet on my test panels from 1985.
Also known as Permanent Violet, Nuremberg Violet or Mineral Violet, Manganese Violet replaced Cobalt Violet in 1890. It is understood to have been first made by E. Leykauf in 1868. It was a cleaner alternative to the Cobalt Violet and was less toxic. It also had better opacity.
The Color of Art Pigment Database: Black Pigments
From CAMEO: A synthetic pigment composed of a double salt of phosphoric acid with manganese and ammonium. Manganese violet was first introduced in Germany in 1868 as Nuernberg violet. By 1890 it was commercially available in England from Winsor & Newton. It has a deep rich violet hue but has poor hiding power and has not been widely used. Manganese violet is lightfast and can be used in all techniques except for fresco.
Pigment Number: PV14, PV48, PV49
Two good brands who might have it would be Michael Harding and Vasari.
— Relatively lean, average drying, transparent
— described as: Non staining w/ low tinting strength and fast drying rate in oils where the cobalt content acts as a drier.
From Justpaint.org: In 1860, Cobalt Violet was introduced and gradually developed, refined, and later created synthetically. Two costly versions, anhydrous cobalt phosphate or cobalt ammonium phosphate, (sometimes combined) were used. Cobalt Violet is toxic and costly to produce, and the weak pigment quickly was replaced by the cleaner, stronger Manganese Violet.
The Colour of Art Pigment Database: for Cobalt Violet
Pigment Through the Ages: Purples and Cobalt Violet : The first real violet pigment prepared by Salvètat in 1859. It is chemically stable, but its rather high cost and low tinting power prevented its wider use in paintings. Not unlike its older sister Cobalt Green, its drawbacks included high cost and weak colouring power, both of which limited its use among painters. It was quickly replaced by the cleaner, stronger pigment Manganese Violet.
Inorganic, semiopaque, permanent pigment made of cobalt phosphate or cobalt arsenite, the latter of which is poisonous. Nontoxic cobalt phosphate is presently used to create this pigment.
Pigment Number: PV23, PV37
This pigment is described as being transparent with a high tinting strength. When used at full strength out of the tube, it’s very dark in value. When mixed with white, it forms bright, opaque tints of purple.
There are blue and red shade versions of this pigment. PV23 produces slightly redder shades than PV37. Because the hue can vary with the conditions of preparation and grinding, it may be offered in red shade, blue shade, and so forth.
Dioxazine Violet has good lightfastness. There may be some concern about it fading or shifting in color in tints and washes. Some artists have reported that PV37, a molecular variant, is more lightfast than PV23.
Dioxazine purple is one of the colors I don’t use because I don’t trust it not to fade as it ages. Manganese violet, cobalt violet, and ultramarine violet are more lightfast than dioxazine purple.
I find no great need in my own work for dioxazine violet or dioxazine purple, since I have cobalt violet, ultramarine violet, and manganese violet to turn to whenever a violet or purple is called for. All of those are rated ASTM Lightfastness I, and have stood up well on my test panels over the years. I would, however, trust Williamsburg’s Egyptian Violet, since Williamsburg has had it tested and found no more than 1.9 Delta Es of change in the Arizona sun test.
Colour of Art Pigment Database: Dioxazine Violet Red shade PV23 and Blue Shade PV37. This website notes that qualifies that with “source, extenders, manufacturing process or impurities also play a role in the lightfastness of this pigment.”