Notebook

Notebook, 1993-

MATERIALS & METHODS - Pigments

Pigments - Definitions


Pigment is a finely divided coloring material which is suspended in discrete particles in the vehicle in which it is used as a paint [thus being opposed to a dye [p. 137] [see Dye], which is soluble in the vehicle]. Pigments are derived from a wide variety of substances, organic and inorganic, natural and artificial. They may be classified according to color, chemical composition, or source. [pp. 137-138]

[Gettens, Rutherford J., [Chemist, Department of Conservation, and Fellow for Technical Research, Fogg Museum of Art/1944 and Head Curator, Freer Gallery Laboratory, Freer Gallery of Art, Washington, DC./1966] and George L. Stout, [Lecturer on Fine Arts and Head of the Department of Conservation, Fogg Museum of Art/1942 and Director, Isabella Stewart Gardner Museum, Boston, Massachusetts/1966.] Painting Materials, A Short Encyclopaedia. New York: Dover Publications, Inc., 1942. 1966. ]



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History. Coloring materials from animal, vegetable, and mineral sources to be used for personal adornment, for decorating tools, weapons,and utensils, and for making pictures were sought by man as early as remote prehistoric times. Most easily procurable were vegetable colors, flowers, seeds, berries, nuts, bark, wood, and roots of plants. Most of these were fugitive and they soon faded when exposed to sunlight. There were notable exceptions, however, like the materials obtained from the madder root, the woad plant, or from the lac insect which, under conditons not too unfavorable, sometimes lasted for centuries. Only slightly less available were the colored earths which included the yellow, red, and brown ochres and clays that abound on the earth's surface in sedementary deposits. Carbon black in the form of soot, charcoal, and even charred bones, could have been found about the most primitive hearth. Such coloring materals as these were known and used as early as there are archaeological criteria. Somewhat less readily availale than the earths were the colored minerals of the heavy metals, but, even so, such brightly colord minerals as cinnabar, orpiment, realgar.....[p. 139]

[Gettens, Rutherford J., [Chemist, Department of Conservation, and Fellow for Technical Research, Fogg Museum of Art/1944 and Head Curator, Freer Gallery Laboratory, Freer Gallery of Art, Washington, DC./1966] and George L. Stout, [Lecturer on Fine Arts and Head of the Department of Conservation, Fogg Museum of Art/1942 and Director, Isabella Stewart Gardner Museum, Boston, Massachusetts/1966.] Painting Materials, A Short Encyclopaedia. New York: Dover Publications, Inc., 1942. 1966. ]



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A Reference for Pigments used in Traditional Tempera Painting - [Thompson, Daniel V., Jr., Research and Technical Adviser, The Courtauld Institute of Art, University of London. The Practice of Tempera Painting. New Haven: Yale University Press. 1936. Fourth Printing, 1946.]



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The Pigments - Colors are the material that deterine most obviously the effect of a painting. In practice, colors are taken to mean the painting material as it is applied--i.e., a mixture of colored substances and an appropriate vehicle. These colored substances are called "pigment." Because they are insoluble, their particles are merely suspended in media or solvents. Some of them are extremely fine and can be so highly dispersed in liquids that they look like solutions. A brush full of madder watercolor rinsed out in a glass of water seems to give a red solution, like a dye. Only after standing for some time will the water become clear again as the pigment settles out on the bottom and sides of the glass. There are only a few exceptional cases where painters use dyes such as clored inks. However, these cannot be counted among the reliable artists' materials. On the other hand, special pigmented inks constitute a separate category. By a skillful choice of suitable components, these inks have been considerably improved in light-fastness, so that they can be used for artistic purposes in certain cases. This will be discussed further in the chapter on drawing techniques.

Dyes can be used to make pigments. This was kown long before the invention of coal-tar dyes made production possible on a lage scale. There are a considerable number of organic dyes in nature that were valued as pigments by the old masters. If a piece of white chalk is dipped in a solution of eosin dye and left in water, a substantial part of the eosin will be extracted, dyeing the water red, and only a small proporiton wil remain in the chalk as a pale pink tint. There are, however, some chemical methods for fixing dyes to a white substrate in such a way that the combination will be insoluble. As this chemical process happens too rarely in nature, it is performed artifically in chemical plants and yields a multitude of pigments of may different hues. There are many white minerals suitable as bases or substrata, e.g., barite, gypsum, and clay, as well as pale varieties of green earth, the color of which will not interfere wih strong dyes. In many cases the bases used are not natural minerals, but are artificialy precipitated during the dyeing process. This process is known as color striking, and pigments thus obtained are sometimes called lakes.

Ocasionally certain dyes will be difficult to fix onto a base, because unsuitable substrates were chosen or, owing to faulty manufacture, traces of soluble dye remained in the igment. These can be dissolvrd later in the vehicle and that means not only in water, but in oils, alchohol, or other liquids usd in painting. In the trade, one speaks of "oil-fastness,' or "fastness to oil, water, spirit," etc. If a pigment dissovles in the medium, it is said to "bleed." This is most unpleasant, [p. 51] as such a pigment imparts its color to any paint applied over it. Some fo the brilliant shades of poster color are particularly prone to bleed in water. Commercial artists will be embararrassed to find that their white lettering on a bright red ground suddenly turns pink. In paintings, such shortcomings can have dire consequences. Most brands of permanent rrd, for instance, are notorious for their bleeding. Many artists may have noticed when using a students' gouache or watercolor box that an orange, green, or violet stain often remains on the interior surface of the lid, quite resistant to all cleaning attempts. Paint from an artists' watercolor box sold in Austria could not be washed out of the paper properly because soluble components had dyed the paper fibers.

Another related case concerns an artist who had been asked to varnish some valuable color reproductions. He spoiled several prints because the solvent of his varnish partly dissolved the red printing color. These examples should suffice. Special care must be taken when using cellulose lacquers as coatings, for otherwise quite reliable pigments will react unfavorably with the strong solvents necessary for them. This is further proof that in case of failures all three basic elements of painting terhnique must be considered. The artist should keep to a small range of reliable pigments, and even within this range he should choose carefully. The followng will aid him in his choice. [pp. 51-52]

[Wehlte, Kurt. The Materials and Techniques of Painting. Translated by Ursus Dix. New York: Van Nostrand Reinhold Company. 1975. ]



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Pigment - Any substance used as a colouring agent, particularly the finely ground particles that when held in suspension in a medium constitute a paint. Most pigments are now manufactured synthetically, but historically they have been made from a great variety of mineral, plant, and animal sources: the brown colour sepia, for example, comes from the inky secretions of the cuttlefish, and ultramarine blue was originally made from the semi-precious stone lapis lazuli. The history of pigments is a highly specialized field with little practical importance today for artists who use commercial paints, but it is often vitally important to the expert in relation to authentication and attribution. [Chilvers, Ian, Harold Osborne, and Dennis Farr, eds. Oxford Dictionary Of Art. Oxford, New York: Oxford University Press, 1988.]



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Pigment - A paint medium as opposed to an ink solution. The word carries connotations of thickness: of opacity as opposed to translucency. [Form, Space & Vision, An Introduction to Drawing and Design. Collier, Graham. Englewood Cliffs, New Jersey: Prentice-Hall, 1985.]



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Pigment - Substance that imparts color to other materials. In paint, the pigment is a powdered substance which, when mixed in the liquid vehicle, imparts color to a painted surface. The pigments used in paints are nearly all metallic compounds, but organic compounds are also used (see LAKE). Most black pigments are organic, e.g., bone black (animal black or charcoal) and lampblack. Some of the metallic pigments occur naturally. The brilliant and beautiful coloring of the rock and soil in some parts of the United States, especially in the Grand Canyon of the Colorado Rivers, the Painted Desert of Arizona, and Bryce and Zion canyons of Utah, is largely produced by such compounds, chiefly oxides. Yellow ocher, sienna, and umber are oxides of iron. Litharge is a yellow oxide of lead. Red lead is also an oxide of this metal. Lead chromate, or chrome yellow, is an important yellow pigment. White lead, or basic lead carbonate, is a pigment long in use; it is rendered more durable by mixture with zinc oxide. Cadmium yellow is a sulfide of cadmium. Ultramarine is an important blue pigment, as is Prussian blue (ferric ferrocyanide). Green pigment is produced by mixing Prussian blue and chrome yellow. Vermilion (mercuric sulfide) is red. Pigments occur in plant and animal bodies. The bright colors of plants, for example, are the result of the presence of such substances as chlorophyll (green) and xanthophyll (yellow), both of which are also found in some animals. Among others are carotene, the yellow of carrots and certain other vegetables, and anthocyanin, which imparts blue, red, and purple to flowers. Blood receives its color from the hemoglobin in the red corpuscles. Coloration of human skin is caused by the presence of pigments (see PIGMENTATION). [Harris, William H., and Judith S. Levey, eds. The New Columbia Encyclopedia. New York and London: Columbia University Press, 1975.]



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Pigmentation - Name for the coloring matter found in certain plant and animal cells and for the color produced thereby. Pigmentation occurs in nearly all living organisms. Almost all plants synthesize their own pigments; animals either derive pigments from plant foods or synthesize them themselves. In plants the major pigments are the carotenes (reddish orange to yellow), the anthocyanins (red, blue, and violet), and the chlorophylls (green). The red and yellow colors of autumn foliage are due to the exposure of the anthocyanins after the green chlorophyll pigments, which usually mask them, have decomposed and faded. The major animal pigments are the hemes (red) of blood hemoglobin, the carotenes, the melanins (black and brown), and guanine (white and iridescent). The latter three produce the surface coloration of most animals. In humans the degree of darkness of the skin, hair, and iris of the eye depends primarily on the amount of melanin present. The presence of hemoglobin and carotene in the BLOOD contributes to skin color. Moles and freckles are caused by high local concentrations of melanin; albinism by a lack of melanin; and some birthmarks, e.g., ´strawberry marks,ţ by an unusual local proliferation of blood vessels (and hence of hemoglobin) near the skin srface. Tanning of human skin results from an increase of melanin production under the stimulation of ultraviolet light. The coloration of an organism may be caused by deposits of organic pigments in the tissues (as in human skin or in plant leaves), by optical effects of the refraction of light rays (as in mollusk shells and in some butterfly wings and bird feathers), or by a combination of both (see COLOR). The different modes are illustrated in the baboon and the mandrill: the predominantly brown coloring is due to melanin, but the red and blue markings are also caused by melanin, in the latter case by the refraction of light due to specific spatial arrangements of the pigment granules in the skin areas involved. The pigmentation of many animals is adapted to their environment anf aids in their survival (see MIMICRY; PROTECTIVE COLORATION). In some animals the pigment is changeable; the flounder and the squid, for example, are capable of adapting themselves to the color of their background and thus often of escaping detection by their enemies. The exact mechanism of such changeability is not clearly understood, but in most cases it is due primarily to visual stimulation. In the squid the chromatophores (containing melanin grandules) are controlled by muscles and can expand from an almost invisible pinpoint to 60 times their original size, giving the whole animal a dark appearance. Pigmentation changes are also at least partially controlled by hormones--as, in part, is pigmentation synthesis itself. Pigments not only provide external coloration but also function in some important physiological processes. In the retina of the eye the pigment cells (rods and cones) adjust or regulate the entering light (see VISION). Among its other functions, carotene operates in the synthesis of vitamins and of chlorophyll. Chlorophyll is essential for plant PHOTOSYNTHESIS. Hemoglobin in the blood carries oxygen for respiration. Chlorophyll and hemoglobin are structurally quite similar, both belonging to the pyrrole group of pigments. [Harris, William H., and Judith S. Levey, eds. The New Columbia Encyclopedia. New York and London: Columbia University Press, 1975.]




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