Italian Brown Ocher Pigment

Italian Brown Ocher is a natural earth pigment in which hydrated iron oxide (primarily goethite) is the principal colorant, typically modified by associated clay minerals and minor oxides. In paint, it produces a warm brown to reddish-brown masstone with moderate opacity and a restrained, earthy chroma. Like other natural ochers, it is valued for its broad compatibility across media and its stability in mixtures and conservation contexts.

Origin and History

Ocher and related iron oxide earths are among the oldest pigments in continuous use, with archaeological evidence of iron-oxide-based colors in prehistoric contexts. Goethite (hydrated iron oxide) is a major yellow-to-brown component in many natural earths; variations in particle size, mineral admixtures, and minor constituents produce the broad range of ocher, sienna, and umber hues used historically in wall painting, tempera, and oil.

Source / Manufacture

Natural brown ocher is produced by mining and selecting iron-rich earth, followed by washing, drying, and mechanical grinding. The principal colorant is hydrated iron oxide (commonly goethite, FeO(OH)), with variable amounts of clay minerals (aluminosilicates), silica, carbonates, and trace oxides that modify hue and working properties. As a natural mineral product, batch-to-batch variation in undertone is expected.

Permanence and Compatibility

Brown ochers are considered among the most stable inorganic pigments. They are generally lightfast and chemically compatible with most artists’ pigments and binders, and they perform well in oil, egg tempera, acrylic, watercolor, and fresco. Natural iron oxide earths are typically unaffected by light and most solvents; strong acids can attack iron oxides and associated carbonates, so acid exposure is not recommended.

Oil Absorption and Grinding

Italian Brown Ocher typically shows moderate oil absorption and grinds readily to a smooth paste. Natural earth pigments may contain a range of particle sizes; extended grinding can increase opacity and smoothness, but may slightly reduce the granular character typical of earth colors. A typical oil absorption range is approximately 23–35 g linseed oil per 100 g pigment (method- and grade-dependent).

Toxicity

Natural iron oxide earth pigments are generally regarded as low hazard in normal artists’ use. As with all dry pigments, avoid inhalation of airborne dust and avoid ingestion. Standard studio hygiene (ventilation, dust minimization, and handwashing) is recommended.

Pigment: Italian Brown Ocher (Goethite)

Our Italian Brown Ocher is from deposits in northern Italy. A yellow to brown hydrated iron oxide mineral is usually present in the oxidized portions of iron ore deposits. It is the most common constituent of many forms of iron oxide. Our brown ocher pigment is finely ground and exhibits a reddish brown masstone. It has good tinting strength and covering power.

Origin and History

Goethite was named for Johann Wolfgang von Goethe (1749–1832), a German philosopher and poet who was also a mineralogist. Goethite has been in continuous use as a pigment since prehistoric times. Evidence of goethite was found in paint pigment samples collected from the Lascaux caves in France. In ancient Greece, “ochre” referred to natural earth pigments in various yellow hues (ocher light, golden, dark, greenish, etc.).

Source

This widespread mineral, consisting of hydrated iron oxide, is encountered practically everywhere on the earth’s surface in the form of concretions, oolites (a form consisting of small round grains cemented together), reniform (kidney shapes), or botryoidal (a form resembling bunches of grapes) accumulations. It is frequently encountered in swampy areas at the head of spring waters and on the bottom of lakes and small creeks. Iron oxides, or earth pigments, as they are often called, are an essential group of inorganic pigments derived from minerals. Iron oxide pigments are yellow, red, brown, and green, but artists know them as ocher, sienna, red oxide, umber, and terra verte. Unlike pigments made in a laboratory, the color of natural iron oxide pigments varies with the composition of the particular segment of earth from which they come. The color of these pigments is derived from three constituents: the principal coloring ingredient, secondary coloring ingredients, and a base. The combination of these ingredients produces the particular color of the earth. The innumerable combinations of these ingredients produce a wide range of yellows, reds, browns, and greens.

Principal Colorant

Iron oxide is the principal color-producing ingredient in the earth. The properties of the particular iron oxide in the earth determine its color. The nature of the iron oxide found in the deposit, rather than its percentage, is critical to the resulting earth color. Most rock contains some iron oxide. Those bearing the least amounts are limestone, white clay, and colorless kaolin. Those containing the highest amounts are the rocks from which metallic iron is extracted.

Secondary Colorants

Calcium, manganese oxides, carbonates, silica, and limestone are common modifiers that affect the specific color of natural iron oxides. Manganese oxide, for example, enriches the brown in numbers.

Base

Nearly all iron oxides are clay-based. Clay is the weathered product of silicate rocks and is extremely varied in composition. As a result, it has numerous effects on the earth’s color.

Our brown ocher, or goethite, is sourced from deposits in northern Italy, specifically the Verona region. It is finely ground and has a reddish-brown masstone. It has excellent tinting strength and good covering power.

Tinting Strength

Relatively large crystals of goethite give the yellow color of this mineral, whereas smaller crystals produce shades of brown. As demonstrated in experiments conducted by K. I. Tolstikhinoy, the chromaticity of natural iron oxide and clay pigments are closely related to the content of iron oxide and, from a mineralogical point of view—the content of goethite. Thus, with the content of iron oxide less than 23%, the luminosities of the tone of pigment compose 40–50%, and the purity of tone 60–70%. With the content of iron oxide from 22 to 74%, luminosities of tone vary in an interval of 25–40%, the purity of tone from 70 to 85%, and with the content of iron oxide more than 75%, luminosity is located in an interval of 18–25%, the purity of tone is 83-90%.

Pigment Characteristics

A characteristic of pigments containing goethite is their ability to change color when heated. Heating ocher, sienna, and umber causes the hydrated iron oxides to lose water and darken in shade while their tone intensifies. At temperatures exceeding 300°C, yellow pigments acquire red-brown tones. The most intense red tones are obtained by calcining goethite at 500–600°C. The color change is directly related to the dehydration of goethite and its transformation into hematite. Prolonged heating at high temperatures causes another change into a mineral of dark gray color—magnetite.

Permanence and Compatibility

Goethite, or brown ocher, does not react with other pigments and is used effectively in fresco, oil, tempera, and watercolors. It is considered permanent with medium to good tinting strength and opacity. It does not react with solvents and is indifferent to alkalis, but is partially soluble in acids.

Oil Absorption and Grinding

Brown ocher moderately absorbs oil when dispersed in this medium. The oil absorption ratio is 23–35 parts by weight of raw linseed oil to 100 parts by weight of pigment. If the measurement were grams, it would require 23 to 35 grams of linseed oil to grind 100 grams of pigment to form a stiff paste.

Toxicity

Brown ocher is not considered toxic.

Pigment: Italian Brown Ocher (Goethite)