Luberon Burnt Sienna is an iron oxide earth pigment that resembles red ocher. Unlike ochers, which generally are opaque, sienna earths are more translucent and warmer. When sienna earth is calcined (roasted) at high temperatures, it loses its water content (hydration), and it becomes burnt sienna. Luberon Burnt Sienna is from the last remaining European company operating the ocher deposits in the French quarries of Gargas and Rustrel nested in a 12-mile-long enclave in the heart of the Luberon Mountains, the ocher country.
Rublev Colours Aqueous Pigment Dispersions are pigments dispersed in water ready to be mixed with water-based mediums. These dispersions are specially made for traditional painting mediums, such as egg, casein, fresco, watercolors, and distemper (glue tempera). They are also ideally suited for use with gesso for making toned grounds for drawing and painting.
Pigment dispersions from Rublev Colours contain only naturally-derived ingredients, in addition to pigment and water, making them ideally suited for traditional and natural mediums. Unlike other pigment dispersions typically made for acrylic medium, Rublev Colours Aqueous Dispersions do not contain coalescent solvents, artificial dispersing resins, and other additives that interfere with natural mediums.
Rublev Colours Aqueous Dispersions make preparing traditional mediums easy; you do not have to hassle with powders, grinding pigments with expensive tools, and calculating pigment-binder ratios to make water-based paint. They make adding the right amount of paint binder simple and easy. For example, preparing egg tempera has never been easier because the dispersion makes measuring the right amount of pigment manageable—you add egg and stir—there's no guessing how much egg to add to the pigment.
|Common Names:||English: burnt sienna |
French: terre de sienne brûlée
German: Gebrannte Sienaerde
Italian: terra di siena bruciata
Russian: сиена жженая
Spanish: tierra de siena tostada
The pigment now identified as burnt sienna is a calcined yellow iron oxide earth pigment generally warmer and more transparent than other yellow earths. In the scientific study of historical pigments, distinguishing yellow earths and siennas is not generally possible. Even in the case of modern pigments, there is often not a clear dividing line between yellow earth and raw sienna.
The pigment sienna owes its name to the Italian city, Siena, in the Tuscany region. An area of rolling hills has been famous for mining and producing pigment since the Renaissance. The localities where sienna earth is found are not confined to the original ones near the town of Siena. Still, earth of similar quality is found throughout Tuscany, Sicily, Sardinia, the Luberon Mountains in France, and the Hartz Mountains of Germany. In the United States, in Pennsylvania, deposits of sienna earths are found, and in the mountain ranges of Virginia, good, rich deposits have been developed. In the European part of Russia, the most widely known sources of sienna earths are the Kudinovskoye deposit in the Moscow region and the Ukholovskoye deposit in Ryazansk province.
Sienna earths have been used as a pigment since prehistoric times, although the name terra di Siena for yellow earth did not appear in painting treatises until the second half of the 18th century.
Iron oxide earth pigments, as they often are called, are an essential group of inorganic pigments derived from minerals. Iron oxide pigments are yellow, red, and brown, but artists know them as ocher, sienna, red oxide, and umber. Unlike manufactured pigments, the color of iron oxide earth pigments varies with the composition of the particular segment of earth from which they come. The color of sienna earth pigments is derived from three constituents: the principal coloring ingredient, a secondary coloring ingredient, and a base. The combination of these ingredients produces the particular color of the earth. The innumerable forms and variations in which these ingredients can combine result in a wide range of yellows, reds, and browns.Principal coloring ingredient
Iron oxide hydroxide is the principal color-producing ingredient in sienna earths. The properties of the iron oxide hydroxide 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 coloring ingredients
Calcium, manganese oxide, carbonic materials, silica, and limestone are some common modifiers that affect the specific color of natural sienna earth pigments. Manganese oxide, for example, enriches the brown in numbers.Base
Nearly all iron oxides have an alumina-silicate (clay) base. 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.
Natural sienna earth is a yellow pigment with a more or less brownish red tinge in the mass tone and a more or less yellowish undertone. It differs from the yellow ocher by having a much deeper color, more than twice the tinting power, containing only two-fifths as much silica, only one-third as much alumina, and from two and one-half to three times as much iron oxide hydroxide, and in addition to this from one to one and one-half percent of manganese oxide, to the presence of which is due the color difference.
Natural sienna earth closely resembles yellow ocher by its composition. The content of iron oxide hydroxide in sienna varies from 40 to 70%, while in ocher, it may be less than 20%. A. H. Church reports the typical constituents of sienna based upon three analyses given by M. G. Hurst: Hygroscopic water 8.2 to 17.5%; combined water which includes traces of organic matter 9.0 to 12.4%; manganese dioxide 0.6 to 1.5%; iron oxide 45.8 to 59.7%; and silica 5.0 to 17.4% [The Chemistry of Paints and Painting, p. 230]. The differences in color between ocher and sienna earth pigments are most likely due to the degree of hydration or quantity of water bonded to its ferric oxide content. These pigments are composed of the minerals goethite and hematite associated with varying proportions of mineral impurities.
Roasting natural sienna produces a significant change in its hue and the depth of its color. The iron oxide hydroxide becomes converted to iron oxide, accompanied by a tremendous increase in the transparency and depth of the color. Our French burnt sienna is roasted in furnaces from natural sienna earths extracted from deposits in the Luberon Mastif, Provence, southern France. It is especially noted for its rich reddish brown color and transparency.Permanence and Compatibility
Burnt sienna does not react with other pigments and is effectively used in fresco, oil, tempera, and watercolors. It is considered to be permanent with medium tinting strength and excellent transparency. It does not react with solvents, is indifferent to alkalis, and is partially soluble in acids.Oil Absorption and Grinding
Burnt sienna requires a large proportion of oil to make it an excellent oil-based paint. The oil absorption ratio is 45–55 parts by weight of raw linseed oil to 100 parts by weight of pigment. If the measurement were grams, burnt sienna would require 45–55 grams of raw linseed oil to grind 100 grams of pigment to form a stiff paste.Toxicity
The pigment is considered non-toxic, but care should always be exercised when handling the pigment so as not to ingest it.
Aqueous Pigment Dispersion: Luberon Burnt Sienna
|Colour Index:||Pigment Red 102 (77491)|
|Chemical Name:||Iron Oxide Hydroxide|
|ASTM Lightfastness Rating|
|Refractive Index:||nα=2.260 nβ=2.393 nγ=2.398|