Ultramarine Blue Pigment and Oil Paint: A Comprehensive Guide for Artists

In the realm of artistic expression, the role of pigment cannot be understated, and among these, Ultramarine Blue holds a place of distinction. This article, accompanied by our latest video from the Rublev Colours YouTube channel, delves into the rich history, chemical intricacies, and practical applications of Ultramarine Blue in oil painting. Designed for the discerning artist, our content offers a comprehensive exploration of both its natural and synthetic forms, providing technical insights and historical context. We aim to enhance your understanding and utilization of this iconic pigment, enriching your artistic endeavors with both depth and expertise.

Color Notes: Ultramarine Blue

1. Understanding ultramarine blue pigment and its use in oil paint for artists. 00:13

   1. Explaining the two ultramarine blue shades: green and red.

   2. Details on the pigment production and behavior with different oils.

2. Differences between two shades of blue pigment in oil paint and their use of walnut oil. 04:32

   1. The difference between the two shades is subtle and more noticeable in oil.

   2. The red shade is made with walnut oil, wetting the pigment better than linseed oil.

   3. The green shade requires less pigment due to better wetting with walnut oil.

3. Understanding the use of burnt sienna and white in oil paint mixing for creating warm shades. 08:40

   1. The use of burnt sienna in oil paint mixing for creating transparent warm shades.

   2. Preparation for the next program on chromatic blocks and the importance of subscribing for updates.

   3. The significance of using lead white for achieving better warm colors in oil paint mixing.

The story of ultramarine blue in art is as deep and captivating as the color itself. This pigment, known for its rich and luminous hue, has been a symbol of beauty and prestige for centuries. Originating from the precious lapis lazuli stone, ultramarine blue was once more valuable than gold. Artists coveted it for its unparalleled depth and brilliance, making it a marker of wealth and status in paintings. The journey of ultramarine blue, from remote mines to Renaissance and modern studios, reflects a fascinating interplay of art, history, and science.

Origin of the Name Ultramarine

The term “ultramarine” is derived from the Latin word ultramarinus, signifying “beyond the sea.” This name reflects the pigment’s exotic origins in Afghanistan, as it was brought to Italy by merchants during the 14th and 15th centuries from far-off mines in Afghanistan. The spread and popularity of ultramarine are primarily credited to the city of Venice, which, in historical times, served as the principal European gateway for the import of lapis lazuli, the source of this esteemed blue pigment.

The Source of Ultramarine: Understanding its Unique Color

The deep color of ultramarine lies in its complex chemistry. At its core, ultramarine is a sodium aluminum silicate with sulfur impurities, which give its distinctive blue color. Ultramarine is one of the most complex mineral pigments, a sulfur-containing compound of sodium-silicate, essentially a mineralized limestone containing a blue cubic mineral called lazurite (the major component of lapis lazuli). Lazurite is the blue component of the decorative rock lapis lazuli, which is composed of many minerals—calcite, pyrite, sodalite, and others—that have been mined as a precious stone for some 9,000 years. The Dana System of Mineralogy considered lapis lazuli to be the dark blue crystals in this rock, but these were renamed lazurite in 1891.

The Colour Index designation of ultramarine is Pigment Blue 29, and the Colour Index number is 77007. The term ultramarine designates both the natural mineral and the synthetic pigment, although today, most distinguish the natural mineral by its name, lazurite, or the rock containing it, lapis lazuli.

The History of Ultramarine

Lapis lazuli, known since ancient Egyptian times as a semi-precious stone and for decorative purposes, was first documented as a painting pigment in sixth and seventh-century A.D. wall paintings in the Bamiyan caves of Afghanistan, close to the primary source of the mineral. Further usage was identified in Persian miniatures from the 13th and 14th centuries and Chinese paintings from the 10th to 11th centuries. Indian mural paintings from the 11th, 12th, and 17th centuries also featured natural ultramarine. In Europe, its most extensive use was during the 14th to mid-15th centuries, particularly in illuminated manuscripts and Italian panel paintings, where its brilliance complemented vermilion and gold. Due to its high cost and labor-intensive extraction process, ultramarine was as expensive as gold, often specified in painting contracts, with patrons sometimes supplying the pigment.

Ultramarine was primarily reserved for the robes of Christ and the Virgin in 14th- to 16th-century artworks, indicating its value and the status of the artist and commission. In some instances, less costly pigments like azurite or even carbon black were used for underpainting, as seen in Byzantine wall paintings and polychrome sculptures. Traditional blue pigments, including indigo, were also used as underlayers for ultramarine.

While Italy used ultramarine lavishly, its use was less extensive in Northern Europe. Azurite was more common in German and Early Netherlandish Schools, with ultramarine used mainly for iconographically significant figures or as a glaze. The late 16th and 17th centuries saw a shortage of azurite, increasing the demand for costly ultramarine. Outside Italy, its scarcity was notable, with minimal usage even among wealthy Spanish painters of the time.

Counterfeiting and adulteration of ultramarine were common, given its costliness. In terms of color mixing, its slightly violet-blue hue made it preferable for creating purples, either through physical mixing with crimson lake pigments or by layering glazes of ultramarine and crimson. Despite these challenges, the use of ultramarine in historical paintings predominantly remains pure, mixed only with white to retain its unique hue.

Modern History of Synthetic Ultramarine

The genesis of synthetic ultramarine blue can be traced back to the observations of Johann Wolfgang von Goethe. Around 1787, Goethe noted the presence of blue deposits on the walls of lime kilns near Palermo, Sicily. He recognized these glass-like deposits as a potential alternative to lapis lazuli for ornamental purposes, although he did not comment on their viability as a grindable pigment.

The path to synthetic ultramarine gained momentum in 1814 when Tassaert observed the spontaneous formation of a blue substance in a lime kiln at Saint-Gobain. This substance bore a striking resemblance to ultramarine. This discovery prompted the Societé pour l’Encouragement d’Industrie in 1824 to announce a reward for the successful synthetic replication of this esteemed color. This challenge was met by Jean Baptiste Guimet in 1826 and Christian Gmelin in 1828, the latter a professor of chemistry at Tübingen. While Guimet kept his method confidential, Gmelin openly published his technique, laying the groundwork for the synthetic ultramarine industry.

The Making of Ultramarine: Traditional and Modern Techniques

The traditional method of creating ultramarine was labor-intensive and expensive, involving heating lapis lazuli with wax, resin, and linseed oil. Modern synthetic production of ultramarine, developed in the early 19th century, has made this once-elusive pigment accessible to all artists. This democratization of ultramarine blue has expanded its use beyond the elite circles of the past, allowing a broader range of artists to explore its rich potential.

In the production of ultramarine blue, selecting raw materials is crucial. This includes iron-free kaolin or a similar pure clay, which ideally should have a silica and alumina content close to the ratio SiO₂:Al₂O₃ as found in perfect kaolin. Should there be a lack of silica, it is compensated for by adding a precise amount of finely divided silica.

The other vital components are:

• Anhydrous sodium sulfate (Na₂SO₄);

• Anhydrous sodium carbonate (Na₂CO₃);

• Finely ground sulfur;

• Charcoal powder, or alternatively, ash-free coal or colophony in solid form.

The manufacturing process unfolds in several stages. Initially, the mixture undergoes heating in an enclosed furnace at temperatures ranging from 700° to 750° Celsius. This environment, enriched with sulfur, carbon, and organic materials, creates reducing conditions, forming a yellow-green intermediate, sometimes used as a pigment.

In the subsequent phase, this intermediate product is exposed to air or sulfur dioxide at temperatures between 350° and 450° Celsius. This step is crucial for oxidizing sulfide sulfur into S₂ and Sn chromophore molecules, responsible for the pigment’s final blue (or sometimes purple, pink, or red) hue.

The production of ultramarine with low silica content involves melting a blend of soft clay, sodium sulfate, charcoal, sodium carbonate, and sulfur. Initially, the mixture appears white but transforms into “green ultramarine” upon adding sulfur and applying heat. During this process, the sulfur combusts, yielding a fine blue pigment. In contrast, “ultramarine rich in silica” is typically produced by heating a concoction of pure clay, extremely fine white sand, sulfur, and charcoal in a muffle furnace. This method produces a blue pigment, though occasionally with a red hue.

Post-reactive heating in a kiln, often in brick-sized quantities, the resultant solid matter is then pulverized and subjected to a washing process, typical of most insoluble pigment manufacturing. The various shades of ultramarine, including green, blue, red, and violet, undergo grinding and are subsequently washed with water to achieve the desired purity and texture.

Sustainability and Ultramarine Production

A significant byproduct of this chemical reaction is sulfur dioxide. Consequently, flue gas desulfurization becomes a necessary part of the manufacturing process to adhere to environmental regulations. Historically, large chimneys were employed to disperse the sulfur dioxide produced during production. This often led to the ultramarine tinting of nearby ground surfaces and roof vents, a telltale sign of the pigment’s presence and production.

The sustainable production of ultramarine blue is a growing concern in the art world. Environmentally friendly methods of synthesizing the pigment are being explored, ensuring that the legacy of ultramarine blue is preserved without compromising the health of our planet. These efforts highlight the art community’s commitment to eco-conscious practices, ensuring that ultramarine blue remains a pigment for future generations.

Natural Ultramarine (lapis lazuli), 64X magnification, cross-polarization	Synthetic Ultramarine, 64X magnification, cross-polarization

Differences Between Natural and Synthetic Ultramarine

Natural ultramarine consists of large particles of blue lazurite combined with accessory minerals, such as calcite and silica (seen as transparent edges or particles in the photomicrograph). Synthetic ultramarine offers a more intense blue compared to its natural counterpart. This is attributed to the smaller and more uniform particle size in the synthetic variant, which allows for a more consistent diffusion of light. Remarkably stable, its color remains unaffected by light and, when used in oil or fresco. However, exposure to weak acid causes the pigment to bleach rapidly, releasing hydrogen sulfide in the process. Interestingly, adding even a modest amount of zinc oxide, particularly to the reddish variants of ultramarine, markedly reduces the intensity of the color, demonstrating the pigment’s sensitivity to chemical alterations.

Properties of Ultramarine Pigment

Ultramarine exhibits surprisingly effective covering capabilities, exceeding expectations given its low refractive index. When used in oil, it serves as a semi-transparent glazing color. Its tinting power is considerable, surpassing older blue pigments like azurite or smalt, though it doesn’t quite match the intensity of modern phthalocyanine blues. Ultramarine retains its distinct, vibrant blue hue when mixed with water-based media, such as gum acacia or egg tempera. However, due to its low refractive index in oil mediums, it tends to appear as a much darker blue when applied in thick layers. For optimal results in oil, ultramarine is either blended with a white pigment to create a luminous opaque blue or applied as a sheer glazing layer atop a lighter underpainting.

Synthetic ultramarine absorbs a moderate to high amount of oil (38 to 42 grams of linseed oil per 100 grams of pigment), which may slow the drying of oil paint and hence is a slow-drying oil color. (The oil absorption value is the weight in grams of refined linseed oil required to convert 100 grams of dry ultramarine pigment by the rubbing together to a coherent mass, which will not smear the glass plate on which it has been rubbed with a palette knife.) It is a highly refractive pigment and is difficult to grind in oil because of its poor wetting properties in oil, although it easily disperses in water.

Permanence and Compatibility

Unlike many pigments that fade over time, ultramarine’s molecular structure makes it remarkably stable and resistant to light and chemicals. This durability has preserved the vibrancy of ancient artworks, allowing us to witness the same vivid blue that inspired artists centuries ago. 

Examinations of easel paintings and illuminated manuscripts have shown that natural ultramarine retains its integrity remarkably well, even in several centuries-old artworks. Generally, ultramarine is recognized for its permanence as a pigment. Despite being a sulfur-containing compound, which typically releases sulfur as hydrogen sulfide, it has historically been combined with lead white without any significant incidents of the lead pigment darkening to form lead sulfide.

However, a condition known as “ultramarine sickness” has occasionally been observed, particularly in oil paintings. This manifests as a grayish or yellowish-gray discoloration on the surface of the pigment. Such occurrences are more common with synthetic ultramarine, especially in industrial uses. The exact cause of this discoloration is a subject of debate among conservation scientists. Possible factors include exposure to atmospheric sulfur dioxide and moisture, the acidity of an oil- or oleo-resinous paint medium, or the protracted drying of the oil, during which water absorption might lead to swelling, increased opacity of the medium, and consequently, whitening of the paint film.

Under normal conditions, synthetic ultramarine demonstrates considerable permanence. Lightfastness testing has confirmed its robustness to light exposure. However, it is notably susceptible to acidic environments. In urban settings with high concentrations of sulfur dioxide or similar acidic emissions, there have been instances where ultramarine blue used in outdoor posters has experienced fading. A notable occurrence of “ultramarine sickness” in synthetic ultramarine on a 20th-century painting was recorded, but the fading of the paint film was primarily attributed to the deterioration of the paint medium rather than the pigment itself. Investigations conducted by Wagner and Mertz in 1930 revealed that ultramarine can be safely combined with white lead, avoiding chemical reaction, as long as the white lead contains minimal lead acetate and the paint medium maintains a low level of acidity.

Both natural and synthetic ultramarine exhibit stability in alkalis under normal conditions. However, it has been noted that synthetic ultramarine can fade when in contact with lime (calcium oxide), such as in the coloring of concrete or plaster. These findings have prompted experts to consider whether the fading of the natural pigment in fresco paintings could be due to interaction with lime plaster.

Notable Uses of Synthetic Ultramarine in Art

As noted by Merimee, a chemist and paint technologist of the same period, Guimet, upon successfully synthesizing ultramarine, promptly distributed samples of this pigment to several artists. Merimee’s accounts include a notable usage by Ingres, who employed Guimet’s synthetic ultramarine in the drapery of a key figure in his work “The Apotheosis of Homer.” This artwork, part of the ceiling decoration in the Musee Charles X at the Louvre, is both signed and dated 1827. This date is particularly significant as it predates Guimet’s official presentation of his findings to the Societe d’Encouragement pour l’Industrie Nationale by a year.

August Renior made extensive use of synthetic ultramarine in the second stage of painting (c.1886) Les Parapluies (National Gallery, London, no. 3268). The first stage of the composition (c.1881) contains exclusively cobalt blue. For example, large amounts of synthetic ultramarine were used in the child’s coat to the right edge of the picture.

In the deepest blues and specific samples of mixed green, Vincent van Gogh used synthetic ultramarine in the Cornfield with Cypresses (National Gallery, London, no. 3861).

Synthetic ultramarine was the subject of Eric Johnson’s painting, Ultramarine Madness.

The Apotheosis of Homer, Jean August Dominque Ingres, 1827, oil on canvas, 386 cm × 512 cm (152 in × 202 in), Louvre, Paris

Wheat Field with Cypresses, Vincent van Gogh, 1889, oil on canvas, 28 7/8 × 36 3/4 in. (73.2 × 93.4 cm), New York Metropolitan

Les Parapluies (The Umbrellas), Pierre-Auguste Renoir, 1880–86, oil on canvas, 180.3 cm × 114.9 cm (71.0 in × 45.2 in), National Gallery and Hugh Lane Gallery, London and Dublin

Ultramarine Madness, Eric Johnson, oil on panel, 53.4 cm × 48.3 cm (21.0 in × 19.0 in), Boston, MA, Private Collection 

Ultramarine Blue: Techniques and Tips for Artists

For artists looking to master the use of ultramarine blue, this section offers practical advice and techniques. Whether blending, layering, or experimenting with different mediums, these tips will help artists harness the full potential of this extraordinary pigment.

Ultramarine blue mixed with raw sienna.	Ultramarine blue mixed with burnt sienna.

Ultramarine blue can be used to create chromatic blacks with umber or sienna. The artist can modulate the color temperature of the black or gray mixture from cool to warm using different proportions of ultramarine and the second pigment.

Upon casual visual inspection, Rublev Colours Ultramarine Blue Green Shade and Red Shade appear identical in oil paint. However, when measured by a spectrophotometer, there are differences in both full shade and tints with titanium dioxide (TiO₂) in a ratio of 1:2. This is seen below in the spectral reflectance curves for both colors in full shade and tints. Spectral reflectance curves are a graphical representation of the spectral response of an object, such as paint, over different wavelengths of the electromagnetic spectrum.

The primary difference between these pigments in oil paint is that the Green Shade is ground in linseed oil, whereas the Red Shade is in walnut oil. This gives each color a different consistency—the Green Shade is long and stringy, while the Red Shade is short and buttery. This behavior can be seen in the videos of each color below.

Health and Safety

No acute or known chronic health hazards are associated with this product's anticipated use (most chemicals are not thoroughly tested for chronic toxicity). Protect yourself against potentially unknown chronic hazards of this and other chemical products by keeping them out of your body. Do this by avoiding ingestion, excessive skin contact, and inhaling spraying mists, sanding dust, and vapors from heating. Conforms to ASTM D-4236.

Notes

Some separation of pigment and oil may occur in Rublev Colours Artist Oils and is a natural process when no wax or stabilizers are added to paint to prevent this from occurring.

All images of color swatches on this website are only approximations of the actual color of the oil paint. We have carefully matched the color in these pictures on calibrated color monitors to the actual color. However, your results may vary because of the wide variance in color monitors.

Color Swatch Note: The color swatch was created with a thick application (left side) of color and a tint (right side) made with equal parts of color and titanium white and applied on acrylic primed cotton canvas.

Drawdown Note: The image of the "drawdown" contains a pre-mixed paint film of 6 mils (0.006 inches) thickness applied to a standard test card to examine color consistency, opacity, and other qualities. The drawdowns show the color's full strength (mass tone) on the left and mixed in a 1:2 ratio with titanium white on the right. The bottom area of the drawdowns is scraped to show undertones.

References

Roy, Ashok. “Ultramarine Blue.” Artists’ Pigments: A Handbook of Their History and Characteristics. National Gallery of Art. Volume 2. pp. 37–66.

Plesters, Joyce (1966). “Ultramarine Blue, Natural and Artificial”. Studies in Conservation. Volume 11. pp. 62–91. doi:10.2307/1505446. JSTOR 1505446.

Boer, J. R. J. Van Asperen De (1974). “An Examination of Particle Size Distributions of Azurite and Natural Ultramarine in Some Early Netherlandish Paintings”. Studies in Conservation. Volume 19 (4): pp. 233–243. doi:10.2307/1505730. ISSN 0039-3630. JSTOR 1505730.

Eastaugh, Nicholas; Walsh, Valentine; Chaplin, Tracey; Siddall, Ruth (2008), Pigment Compendium—A Dictionary and Optical Microscopy of Historical Pigments, Routledge, pp. 585–587, ISBN 978-0-7506-8980-9