Virgil includes ultramarine blue, cobalt blue, and cerulean blue on his portrait palette when there’s a sky in the background to paint.
On the subject of blues, in my own work I find it necessary to mute them in the interest of bringing them into harmony with the other colors. This usually involves adding a bit of blue to a larger quantity of grey made from white and black. High-chroma blues are beautiful from a decorative standpoint, but they tend to “jump out of the picture at you,” meaning they can disrupt color harmony if they are used any more extensively than minor accents.
For the first layer in my own work, any blue I use will be mixed with lead white and Mars black or bone black (aka “ivory”) black, with the blue paint generally no more than 50 percent of the mixture.
Cobalt or cerulean blues are the most lightfast blues, thus I’d favor them if they would work with the overall color scheme.
It’s very rare that I would use any blue at full chroma except for small accents because it tends to disrupt the color harmony and “jump out of the picture.”
If I’m painting in multiple layers, I most often underpaint the areas that are to be blue in greys made from lead white and Mars black, and then only bring blue into it in the final layer over the dried grisaille.
Greys made with black and white read as if they were blue in a picture whose dominant colors are yellow, orange, red, and brown.
Color harmony is easier to achieve when grey represents blue in a painting with warm (yellow, brown, orange and red) dominance.
What blues to use depends on what you want to paint. The ones I find myself using most are cobalt blue, cerulean blue, and ultramarine blue (red shade), but rarely do I use any of them straight. I mix them with greys made with white and black, or just bone black, and then they harmonize better with the other colors. I have several tubes of manganese blue, but very seldom do I see a need for it. If I ever do another moonlight scene, it might be good there.
Pigment Number: PB27
Prussian blue is quite different from ultramarine, so would not make a good substitute for it. Prussian blue inclines toward green, whereas ultramarine inclines toward purple. If you need blue in your paintings, you’ll probably need ultramarine too.
From the JustPaint.org article, “Some Historical Pigments and their Replacements”: “Prussian Blue is of significant importance in the art world as it is known to be the first man-made pigment. It was invented accidentally by the Berliner Diesbach in 1704, when he was trying to create a Florentine Lake. Also known as Chinese Blue, Berlin Blue, Paris Blue, Steel Blue, Iron Blue, Bronze Blue, Paste Blue, and Milori Blue. The Milori Blue variety is typically what makes up today’s Prussian Blues. The pigment is alkali sensitive, and therefore cannot be made in an acrylic emulsion.”
The Color of Art Pigment Database: Blue Pigments
The Conservation and Art Materials Encyclopedia Online (CAMEO): Prussian Blue
Pigments Through the Ages: Prussian Blue. A short description: “Dark blue, called the first of the modern pigments. It has very high tinting strength but is only fairly permanent to light and air. It’s an Iron-hexacyanoferrate accidentally formed while experimenting with the oxidation of iron. The pigment was available to artists by 1724 and was extremely popular throughout the three centuries since its discovery.”
Pigment Number: PB29
Natural ultramarine blue pigment is the ground, separated blue particles (Lazurite) from the gemstone Lapis lazuli.
Preparing the pigment was a time-consuming process. For details, The Conservation and Art Materials Encyclopedia Online (CAMEO): Ultramarine Blue, Natural.
Synthetic ultramarine was discovered in 1826 in France by Jean-Baptiste Guimet and sold commercially in 1828. Its particles are finer and more regular in size and shape than the natural ultramarine pigment. It’s also inexpensive. For details, The Conservation and Art Materials Encyclopedia Online (CAMEO): Ultramarine Blue, Synthetic.
Lapis Lazuli vs Ultramarine Blue
Although Lapis Lazuli (after purifying) and Ultramarine Blue are essentially the same chemically, Lapis Lazuli is the natural mineral source and has different working properties. It also contains iron pyrite crystals that can give it a slight ‘sparkle’. Lapis Lazuli is also a much more expensive pigment so it is misleading to label Synthetic PB29 as Lapis Lazuli. Extraction from the rare semi-precious gem stone is labor intensive & time consuming.
Natural ultramarine is descibed as being semi-transparent, average drying, low oil content, low tinting power, non-toxic. By comparison, synthetic ultramarine has much more tinting and covering power with higher chroma. Synthetic ultramarine does not have the same appearance as lazurite (lapis lazuli) due to the particle size of the pigment.
Other descriptions artist provided: The natural versions are not as chromatically intense. They tend to gray out and cool slightly vs the synthetic version (this is mixing them to give the same value in the tint – not just adding the same amount of white to each). Another big difference is that the natural ones have very low tinting strength whereas the synthetic versions are very strong tinters.
True lapis lazuli (real ultramarine blue) is closer in color to the deeper shades of cobalt blue than it is to synthetic ultramarine.
A note on why Ultramarine has high tinting strength: According to George O’Hanlon, it has a low refractive index (RI 1.51) relative to that of linseed oil (1.48) [which means it should be more transparent because its refractive index is nearly equal to the medium] and it does not scatter light efficiently. However, it absorbs a large amount of the visible wavelengths of light (particularly red and green wavelengths), so it has high tinting strength.
The Color of Art Pigment Database: Blue Pigments
The Pigment Through the Ages website describes the historical use of ultramarine and the process for making the pigment, both natural and synthetic. See Ultramarine.
A YouTube video on how lapis lazuli pigment is made.
“The Celestial Stone“, an article on the mining of lapis lazuli and art history.
Pigment Number: PB28
Cobalt blue is one of the most lightfast of the blue pigments, and from that perspective is not adequately replaced by mixtures of phthalocyanine blue and synthetic ultramarine, neither of which are as lightfast.
The Colour of Pigments Database: Cobalt Blue
Pigments Through the Ages: Cobalt Blue: “It’s a cobalt oxide-aluminum oxide. Very costly and extraordinary stable pigment of pure blue colour discovered by Thénard in 1802. It is now the most important of the cobalt pigments. Although smalt, a pigment made from cobalt blue glass has been known at least since the Middle Ages, the cobalt blue established in the nineteenth century was a greatly improved one.”
Pigment Number: PB35
Virgil uses Cerulean Blue from Williamsburg.
Real Cerulean Blue (PB 35, cobalt stannate) is a compound of cobalt and tin. It’s an expensive pigment with good lightfastness. Mixing it thoroughly with a small amount of linseed or walnut oil will bring it to a smooth, controllable consistency. It’s useful for painting flesh tones of light-complected people.
Beware of a paint labeled: “cerulean blue hue”. It’s a mixture of phthalocyanine blue and zinc white or titanium white, or both. If it isn’t real cerulean blue, it isn’t worth trying to save or use. Fake cerulean made with phthalocyanine blue does horrible things in flesh tone mixtures.
If you don’t know whether your cerulean blue is genuine, check the pigment information on the tube somewhere. The pigment number for zinc white is PW 4; for titanium dioxide, it’s PW 6. If either of those is there in the tube, it’s not real cerulean blue. If PW 4 is in ANY oil paint, the soundest practice is not to use it.
Note: there is also PB36 made from oxides of cobalt and chromium. Some paint manufacturers label it cerulean blue but the proper name should be cobalt chromite blue. PB35 is opaque whereas PB 36 is more transparent, has higher tinting strength, and is darker in value than PB 35.
The Colour of Pigments Database: Cerulean Blue
Pigments Through the Ages: Cerulean Blue: “It’s a cobalt stannate which was introduce as a pigment in the 1860s. Very stable and lightfast greenish blue with limited hiding power. Cerulean blue has a fairly true blue (not greenish or purplish) but it doesn’t have the opacity or richness of cobalt blue. It was not recommended for use in watercolor painting because of chalkiness in washes. In oil, it was particularly valuable to landscape painters for skies.”
Pigment Number: PB33
The production of Manganese Blue pigment PB33 was discontinued in the 1990s, so tubes of manganese blue are harder to find now than they were a few years ago. I would reserve it for the final layer in multiple-layer paintings, and only use it where no other blue would work. Its tinting strength is low, so to use it in mixtures would be essentially to waste it. It’s best used alone as a glaze.
The Color of Art Pigment Database: Manganese Blue. The pigment is described as: “a brilliant, clear, semi-opaque to transparent blue pigment with a greenish undertone. Its saturation and texture varies across manufacturers.”
According to the Conservation and Art Materials Encyclopedia Online (CAMEO): Manganese blue accelerates the drying of oil paints but has poor tinting strength.
A note about the original Manganese Blue from Gamblin’s Just Paint article on historical pigments and their replacements: “Manganese Blue, or Barium Manganate, has been produced since the 19th century. The synthetic variation was patented in 1935, but neither variety is commonly produced anymore, as the coarse, weak pigment was replaced by more intense blues.”
The Vasari paint company notes: Introduced in the mid 1930’s, the Barium Manganate pigment was manufactured from the mined ore for only about 50 years. Even so, true Manganese Blue gained a devoted following among painters, and was highly prized for its intense beauty and brightness.