Northern
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Specializing
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Northern
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Specializing
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Phoebe Dent Weil / Northern Light Studio, LLC
1602 Locust Street, Suite 815-A, St. Louis, MO 63103 / (314) 588-9680/ PDWeil@aol.com
http:/ /www.northernlightstudio.com
Prepared for the St. Louis Art Museum Class on Italian 1 ~ c. Painting Techniques 31 August-5 October 2002
CHALK: [CaCO3] (whiting)-occurs naturally-Largely composed of remains of minute sea organisms.-- Fairly transparent when mixed with oil, it was used primarily in the Netherlands as body pigment for priming (mixed with animal glue) and as an extender in lead white (ceruse, loodwit=60% leadwhite and 30% chalk)
GESSO: [Calcium sulfate] Gypsum, Plaster of Paris soaked in excess water to prevent it from setting, combined with animal glue and applied to wooden panels or other supports for painting or gilding. Used typically in Italy.
LEAD WHITE: (It. biacca, flake white, Cremnitz white) TOXIC--basic lead carbonate [2PbCO3 .Pb (OH)2] --made by exposing lead to vinegar vapor and subsequently to CO2 in the open air, as described by Theophrastus, Pliny and Vitruvius -though also found in nature as the mineral, cerussite-Manufactured by the 'Dutch' or 'stack' process. Cremnitz white is prepared by the action of carbon dioxide on litharge (PbO), considered whiter, denser, and more crystalline than ordinary, Dutch process white lead. When heated at moderate temperature turns bright yellow because of the formation of massicot (FbO); higher temperatures melt the massicot and change it to litharge and even further oxidize it to red lead. Ceruse refers to a combination of lead-white and chalk. Poisonous if inhaled as a dust or ingested.
CHARCOAL BLACK (It. negro carbone):-(vine black) -made from the residue of dry distillation of wood by heating the wood in closed chambers or kilns. It has a blueish tone. Under the microscope it is easy to distinguish the plant fibers.
BONE BLACK (It. negro d'osso): (and ivory black) -made of ivory or bone burned in closed retorts, consisting of carbon and calcium phosphate [C .Ca3(PO4)2]. Usually bones from glue stock, boiled to remove fat and glue, are used. Ivory black is considered the deepest black of all.
ULTRAMARINE (LAPIS LAZULI, It. azzurro, azzurro oltramarina): -is a precious stone of a deep blue color with white veins of quartz and golden glittering flecks of pyrite. The blue mineral is a complex sodium-aluminum-silicate containing sulfur. The blue color is due to the sulfur ion. Cennino Cennini gives a method for purifying the mineral for use as a pigment. To obtain a pure blue pigment, the stone is crushed and ground and then separated from the impurities making use of the different affinity to fat and water of the various components. Quartz and pyrite are slightly less hydrophilic than the blue ultramarine. By mixing the powder into a paste of wax and oil and subsequently slowly releasing it into lukewarm water, the more hydrophilic ultramarine comes out first, quartz and pyrite stay behind. The process is very time-consuming: the stone, to start with, is expensive, so the resulting blue pigment is very expensive indeed. It is therefore used with great care. One way to economize on ultramarine was to put it over a dark under-layer or over smalt. It was usually tempered with walnut or poppy oil, neither of which yellowed as much as linseed oil, and thinned with turpentine, or oil of spike to make a lean paint. Synthetic manufacture begins around 1830. Is permanent to light, stable in fresco. Since the refractive index of ultramarine is so low, it serves better and is far brighter in tempera than in oil. It is discolored in an oil or a varnish film as they yellow with age producing a greenish appearance. Ceneri d'azzurro, or "ultramarine ashes", a residue of ultramarine after the purest particles have been extracted.
AZURITE (It. Bice): -basic copper carbonate [2CuCO3 .Cu (OH)2] It occurs in mines of copper and silver, frequently together with malachite. Ground coarsely because fine grinding causes it to become pale and weak in tinting strength. Traditionally most used in a tempera medium because in oil it darkens and becomes muddy.
SMALT (It. Smalto): -a blue glass containing cobalt as coloring ingredient, popular because of its low cost. If ground too fine, it loses its color, therefore the particles of smalt found in paint layers are usually quite large. Smalt discolors in oil, as the cobalt migrates out of the glass into the oil, leaving behind an olive green unsightly color. It eventually deteriorates to a mottled gray color because of reaction of the alkali content of the smalt with the oil medium. The admixture of lead white prevents discoloration to a degree. Smalt was used in the Delft ceramic industry as the blue color in Delft tiles.
INDIGO: -is present in various plants, not only in the East Indian indigo plant, but also in woad. It is the most important plant dye. The dye occurs in the plant as the colorless glucoside indican, and is extracted with hot water. Contact with air oxidizes it to its blue form indigotin, which is insoluble in water. Various recipes recommend grinding indigo with lead white and gum arabic or egg white to produce a pigment, that can be used in oil. On its own it appears very black when used in oil.
LEAD-TIN YELLOW (GIALLORINO or GIALLOLINO): [pb2SnO4] TOXIC -a lemon yellow to slightly orange-pink synthetic pigment, used mainly during the 15th to 17th century. Massicot or litharge refer to the yellow monoxide of lead (PbO) made by gentle roasting of white lead. Massicot and litharge refer to the yellow monoxide of lead (PbO). Minium the red tetroxide of lead (Pb304), is made by heating litharge or white lead. Poisonous if inhaled as a dust or ingested.
LEAD-TIN-ANTIMONY YELLOW: [ternary oxide of lead, tin and antimony] TOXIC-unlike Naples yellow which is pure lead antimonate- This pigment, warmer hued than lead-tin yellow, was identified as that used by Orazio Gentileschi for the yellow dress of the Lute Player and in St. Cecilia and an Angel in the National Gallery in Washington. It appears to be restricted in use to Italian painting and specifically to paintings produced in Rome. (see article by Ashok Roy and Barbara H. Berrie, "A New Lead-Based Yellow ...."
YELLOW OCHER (It. Terra gialla): (and red ocher) The ochers are naturally occurring earths, consisting of silica and clay, which owe their color to the presence of iron oxide. Fe203 anhydrous, is red, whereas the hydrated form, Fe203 .H2O, is yellow. By burning yellow ochre the water is driven out and the color changes to red and even to purple. Caput mortuum is the name for stronger burnt dark purple varieties of iron oxide. Raw sienna contains the same hydrated iron oxide as yellow ocher, but it is semi-transparent due to the presence of alumina and silica.. Burnt sienna contains anhydrous iron oxide like the red ochers but it is semi-transparent.
YELLOW LAKE: (schietgeel, Dutch pinke)-made from Buckthorn berries, of which the colour is extracted with potash and fixed onto a substrate of aluminum hydrate. This is fomled by adding a solution of alum to the alkaline color extract. Yellow lake in oil is perfectly transparent since the refractive indices of aluminum hydrate and oil are very close to each other. Unfortunately the yellow color in schietgeel, rhamnetin, is not light-fast, causing the yellow glaze to fade, and if over a blue underpaint to produce green, the blueish color underneath will become dominant.
WELD: -natural yellow dyestuff, obtained as a liquid or as a dry extract of the herbaceous plant, Dyer's Rocket (Reseda luteola) formerly cultivated in central Europe. Buckthorn (giallo santo) was another source of yellow dye, also fugitive.
ORPIMENT (Auripigmentum): [As2S3] TOXIC.-yellow sulfide of arsenic, occurs naturally, also made artificially. Bright yellow, sometimes almost orange color, with crystalline, glittering appearance. Used as a fly killer mixed with honey (Symonds MS). Realgar, the natural orange-red sulphide of arsenic [As2S2] is closely related chemically and associated in nature with orpiment.
INDIAN YELLOW: -a yellow organic extract formerly prepared in India from the urine of cows that were fed on the leaves of the mango-now made synthetically.
COCHINEAL: -natural organic dyestuff made from the dried bodies of the female insect Coccus cacti, which lives on various cactus plants in Mexico and in Central and South America. First brought to Europe shortly after the discovery of those countries. The coloring principle of cochineal extract is carminic acid [C22H20013] which gives a scarlet red solution with water and alcohol and a violet solution with sodium hydroxide. The cochineal lakes are not permanent to light. In oil, however, they are fairly stable.
RED OCHER (It. Terra Rossa): -see above, under yellow ocher-conventional use with charcoal black and lead white to make a warm colored imprimatura.
MINIUM (It. Minio): [Pb304] :TOXIC -bright orange-red pigment made by heating lead white or litharge -siccative properties
VERMILION (cinnabar, It. Cinabro): [HgS] TOXIC-mercury sulfide-Found naturally as the mineral cinnabar which is the principal ore of the metal mercury. Pliny referred to it as minium which later came to refer to red lead. It comes in various shades of red according to its method of preparation. It is one of the heaviest pigments, having excellent body and hiding power. It goes black after prolonged exposure to strong light. Strictly speaking, "cinnabar" should refer to the natural product, while vermilion should apply exclusively to the artificial product (heating black mercuric sulfide). Poisonous if inhaled as a dust or ingested.
MADDER LAKE (It. Lacca) (alizarin crimson): -derived from the name of the insect "coccus lacca". Madder lake is a natural dyestuff from the root of the madder plant (rubia tinctorium )-- formerly cultivated extensively in Europe and Asia Minor-The coloring matter is extracted from the ground root by fermentation and hydrolysis with dilute sulfuric acid. Madder lake and rose madder for artists' pigments are prepared from the madder extract by adding alum and precipitating with an alkali. Synthetic manufacture begins in 1868. [Gettens & Stout, p. 126 f.]
GREEN EARTH (terra verde): -an earth occurring naturally near Verona, also in Tyrolia and in Bohemia-The coloring ingredient is iron present in the minerals glauconite and celadonite. They are compatible with all binding media, but they have very low hiding power in oil.
VERDIGRIS (It. Verde Tame) (Vert de Grece): -basic copper acetate-Known in ancient times, its preparation was described by Theophrastus and Pliny. Prepared by exposing sheets of copper to vinegar vapor. The resulting copper acetate is scraped off and the copper sheet placed back over the vinegar. Verdigris was used in oil, even though there are many warnings against using it in the treatises from the 16th c. onward, as it turns dark brown. It is the most reactive and unstable of the copper pigments.
COPPER RESINA TE:-a transparent, amorphous green of copper salts of resin acids formed when verdigris-basic or neutral copper acetate-reacts with a varnish. It is made by heating and dissolving copper acetate in colophony (rosin) and Venice turpentine resins. Balsam or other similar resins may be used as well. It produces a transparent green glaze.
MALACHITE: [CuCO3.Cu (OH)2] -basic copper carbonate, similar in composition to azurite except containing more combined water. Perhaps the oldest known bright green pigment.
UMBER (It. Terra d'ombra): Natural umber is a greenish brown earth color, which in addition to iron oxides contains manganese oxide. This renders it a very good siccative for oil. The best umber comes from Cyprus. Mixing umber with white produces very beautiful shades of gray. Burnt umber has a dark reddish brown color, producing interesting tones of pink in mixtures with white. Because of their manganese content the umbers dry well in oil. The umbers were frequently used for grisailles or painted reliefs.
ASPHALTUM (It. Spalto) Lor BITUMEN also SPALTE, ASPALATHUM: "-a brownish black, native mixture of hydrocarbons with oxygen, sulphur, and nitrogen, and often occurs as an amorphous, solid or semi-solid liquid in regions of natural oil deposits." (Gettens and Stout, p.94) Prepared by heating in a drying oil, bitumen tends to absorb the oil to produce a rich, transparent brown that never completely dries, and ultimately causes serious cracking in the paint layers. Identified by Ann Massing in a painting by Orazio G.(see: A. Massing, "Orazio Gentileschi's Joseph and Potiphar's Wife)
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