Closest to a primary blue in that it is neither ‘greenish’ nor ‘purplish’, Cobalt is a lovely but expensive pigment. Look for the genuine PB28 for the most beautiful and liftable granulating washes. Some artists prefer cobalt to the deeper Ultramarine as a basic blue. I have it as an ‘extra’.
Blue Pigments
Virgil includes ultramarine blue, cobalt blue, and cerulean blue on his portrait palette when there’s a sky in the background to paint.
Virgil’s Assessment
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.
Prussian Blue
Pigment Number: PB27
Virgil’s Assessment:
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.”
Technical Links:
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.”
Opacity Rating:Transparent
Lightfastness Rating: I – Excellent
Oil-To-Pigment Ratios: High in Oil Content
Tinting Strength
Toxicity: Low Hazard
Drying Rates: Very Fast
Ultramarine Blue
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.
Virgil’s Assessment
True lapis lazuli (real ultramarine blue) is closer in color to the deeper shades of cobalt blue than it is to synthetic ultramarine.
Technical Links
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.
Cerulean varies from brand to brand but generally behaves as a cool blue making bright greens. Genuine Cerulean PB35 is slightly warmer than my preferred Cerulean Chromium PB36 DS. It is a rather opaque colour with plenty of granulation and particularly useful for skies and for mixing opaque greens.
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| Cerulean Blue Derivan, Cerulean Blue W&N, Cerulean Blue (Hue) Da Vinci, Cerulean Blue DS |
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| Cerulean Genuine DV, Cerulean Blue Chromium DS, Cerulean Blue Deep OH, Cerulean Blue Genuine DV |
Phthalo Blue
A cool and staining blue, phthalo blue is a very common colour in any palette. Available in Green Shade and Red Shade versions, with the green shade being the most common. Phthalo Blue Red Shade is another primary blue option if transparency, staining or non granulating properties are desired.
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| Winsor Blue W&N, Phthalo Blue GS DS, Phthalo Blue GS DV, Phthalo Blue MG, Richeson Blue (Phthalo) SQ, Phthalo Blue RS DS. |
Prussian Blue
Not one of my favourites, Prussian Blue is an alternative blue if a less staining cool blue is desired. Made from PB27. Easily mixed with Phthalo Blue and a warm red.
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| Prussian Blue MG, Prussian Blue W&N, Prussian Blue DS, Prussian Blue DV |
