Cobalt Violet

What color is cobalt violet?

The story of cobalt violet

Cobalt violet was the first purple a painter could trust, and for a century it was also the one nobody could afford.

A competition produced it. In 1859 the industrial society of Mulhouse asked for a violet that could be printed on cloth, and a chemist named Alphonse Salvetat answered with cobalt phosphate, a compound Louis Jacques Thenard had used as a stepping stone to cobalt blue back in 1802. Salvetat, who taught ceramics and had written a textbook on it two years earlier, noticed that the same powder came out in different shades depending on how hot you fired it. Fired hard, it was a deep reddish violet. Until then painters had mixed their purples from a red and a blue, as they had since the Middle Ages.

There was a catch, and it was older than Salvetat. A lighter, pinker cobalt violet already existed: cobalt arsenate, the same compound as the mineral erythrite, known since around 1800 and one of the most poisonous pigments ever put in a tube. The phosphate displaced it, but slowly; the arsenate stayed in some paint lines into the twentieth century. Monet's tubes, at least some of them, were the old kind. When the Art Institute of Chicago analyzed his Water Lily Pond of 1900 and his Water Lilies of 1906, it found cobalt violet in the purples, and the cobalt came with arsenic. He was painting lilacs with poison.

Today's cobalt violet is the phosphate, PV14, sold as light and deep, plus ammonium and lithium cobalt phosphates for the pinker end. All of them are lightfast, weak and dear, because cobalt is expensive and the pigment cannot be ground fine without losing its color. That weakness cost it the market: manganese violet, a stronger color, took over, and Monet leaned on it for the shadows of his Rouen Cathedral series. Cobalt violet survived as a luxury, a granulating, lifting, pale-tinting purple that looks like light rather than paint.

Its green cousin is older and shyer. In 1780 the Swedish chemist and mining expert Sven Rinman found that cobalt oxide baked into zinc oxide made a soft, slightly bluish green, and Rinman's green, PG19, has been made ever since. It is a weak colorant and dear next to chromium oxide green, so it never became anyone's everyday green. What it has is texture: a cool, misty green that settles into the paper like lichen on a wall. A cobalt titanate version, PG50, is grayer and colder, with more body.

Turquoise came last. Cobalt teal and cobalt turquoise are spinels, cobalt fired with titanium or with chromium and aluminum, PG50 and PB36, and PB36 is sometimes sold as a cerulean because it is a darker, greener take on the same idea. They are the granulating turquoises, the color of shallow tropical water. Between cobalt blue, cerulean, the greens, the teal and the violet, the cobalts are the one family where every member granulates, lifts and costs too much. I own the violet and the teal, and I use them the way you use good vinegar, in small amounts and on purpose.

Pigment facts

These describe the pigment in general. Every brand's tube behaves a little differently, so test yours on scrap paper.

How to mix cobalt violet

You can mix a violet close to cobalt violet's hue from ultramarine and a quinacridone rose, but it will be stronger, smoother and flatter, and it will stain. What you cannot mix is the texture. Cobalt violet granulates and lifts, and no organic mixture does either.

Pair it with cobalt blue. Both granulate, both are semi-transparent, and together they make the lilac-gray shadows on snow and white walls that the Impressionists were after; use cerulean instead and the shadow turns toward a dusty turquoise. For a warm gray, a speck of yellow ochre does it.

Using cobalt violet in watercolor

Use cobalt violet for light, not for dark: the lilac in a cloud shadow, the pink-violet of a hill at sunset, the shaded side of a white flower. It is a delicate color and it is at its best when it is barely there.

Wet-on-wet suits it. Drop it into a damp sky wash and it will granulate as it dries, settling into the paper like weather. It also separates from a smoother pigment in the same wash: cobalt violet dropped into a wet phthalo blue makes a two-texture sky in one pass.

It pairs with the earths and the greens. Next to yellow ochre it looks fresher; beside cobalt green the two textures match, and the pair makes the softest landscape distance I know.

One thing I learned the hard way: do not expect it to hold its own in a mix. Cobalt violet is so weak that a strong color swallows it whole; a speck of phthalo anything and the violet is gone. Mix it with other quiet colors, or use it alone.

Cobalt violet vs cobalt green (and cobalt teal)

All three are cobalt fired with something else: phosphate for the violet, zinc oxide for the green, titanium or chromium for the teal. They share a temperament: lightfast, granulating, weak in the mix, and never cheap. Cobalt violet is for light and flowers, a reddish violet that no other pigment matches for delicacy.

Rinman's cobalt green is the shy one: a cool, grayish blue-green with low saturation, made for the misty middle distance of a landscape and for lichen on stone. Cobalt teal is the showy one: a clean turquoise between cerulean and viridian that reads as tropical water from across the room, and the one beginners fall for first.

If cobalt violet is the light on a lilac at dusk, cobalt green is the moss under the tree, and cobalt teal is the swimming pool you can see from the plane.

More color stories

Mel, founder of Tobio'sI make portable watercolor kits and I named the company after my cat. I write these pages for the beginner I used to be, one pigment at a time.