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OF APPLYING SUPERFICIAL COLOR.--Painting, Colors, Preparation, Application, Crayons, Water Colors, Distemper, Paper Hangings, Flock Paper, Fresco, Encaustic Painting, Oil Painting, Varnishing, Japanning, Polishing, Lackering, Gilding, Photography. OF CHANGING INTRINSIC COLOR.--Bleaching, Dyeing, Mordants, Dyes, Calico Printing.

An extensive branch of industry has for its object the effecting of changes in the natural colors of bodies. The artificial modifications, produced in color, may be either mechanical and superficial, or chemical and intrinsic. In painting, gilding, and similar processes, the original color of a substance is not altered, but it is mechanically concealed by another substance which covers it from view. On the other hand, in bleaching and dyeing, the color of the whole substance is intrinsically changed, by a chemical action. This difference of character has given rise to distinct arts in coloring, the processes of which are for the most part dissimilar.


Painting.--Common painting, when disconnected with design, has for its object to produce a uniform and permanent coating upon surfaces, by applying to them a compound, which is more or less opaque. In many cases painting is applied only for ornament, but it is more frequently employed to protect perishable substances from the changes to which they are liable when exposed to the atmosphere, and other decomposing agents. The effect and durability of different coverings employed in this way, depends upon the kind of pigment used, and still more upon the vehicle, or uniting medium, by the intervention of which it is applied.

Colors.--The coloring substances, employed by painters, comprise a great variety of articles derived from the mineral, vegetable, and animal kingdoms. They are employed in a state of minute subdivision, and commonly mixed with a fluid which is more or less viscid and tenacious. When applied upon the surface of canvass, wood, or other bodies, they communicate their color, by covering and concealing the original color of the surface, while they substitute their own instead. Those which are perfectly opaque, are called body colors, such as white lead, and vermilion; while those which are partially pellucid, are called transparent colors, as prussian blue, terra di sienna, and lake. Transparent colors do not wholly conceal the colors beneath them, but produce the combined effect of the two. The process called by painters glazing, consists in laying a transparent color over one of a different tint. Transparent colors are sometimes mixed with a white earth, to give them a body, where it is necessary to cover entirely the previous surface. Common whiting is usually employed for this purpose.

The following list comprises the principal coloring substances, used as paints, exclusive of those which belong only to the art of dyeing.

BLUES.--Ultramarine is the richest and most durable of all the blues. It is not altered by time, and bears exposure to a red heat without changing its color. It is made only from the lapis lazuli, a stone brought from several parts of Asia, which bears an extremely high price.

Prussian blue is a strong and durable color. In the present language of chemistry, it is a ferrocyanate of the peroxide of iron. It is made from blood, and other animal matters, dried, and heated to redness with an equal weight of pearlash. The residue, which consists chiefly of cyanuret of potassium, and carbonate of potass, is dissolved in water, and after being filtered, is mixed with a solution of alum and protosulphate of iron. A greenish precipitate ensues, which, by exposure to the atmosphere, passes through different shades, till it arrives at a fine blue color.

Blue verditer is a nitrate of copper combined with hydrate of lime. It is made by adding quicklime to a solution of copper in nitric acid, and mixing the precipitate with a small portion more of lime. It is a full blue, much used in paper staining, but is liable to grow dull.

Smalt is a powdered glass, which derives its blue color from the oxide of cobalt. It is chiefly used by strewing it on a ground of some other color.

Bice consists of smalt finely levigated. It is rather lighter, and very durable, but not extensively used.

Indigo is the deepest of all the blues in common use. It is very durable, but more used in dyeing (which see) than in painting. Stone blue, Fig blue, Queen's blue, &c., consist of indigo reduced by starch.

REDS.--Vermilion is a bisulphuret of mercury, formed by fusing sulphur with about six times its weight of mercury, and subliming in close vessels. The product is called Cinnabar, and, when powdered, vermilion. It is of a bright scarlet color, and stands tolerably well.

Red lead, otherwise called minium, is a deutoxide of lead, formed by exposing lead, or litharge, to heat in a furnace, in open vessels, with a current of air passing over it. The metal is gradually converted into an oxide of a bright orange red. Red lead is extensively consumed in the manufacture of flint glass. As a pigment, it is brilliant at first, but liable in time to turn black.

Chrome red is a fine scarlet, formed by boiling carbonate of lead with an excess of chromate of potass. By Dulong's method, sixty-seven parts of white lead are boiled with eighty-two parts of chrome yellow, in water.

Colcothar, also called crocus martis, and rouge d'angleterre, is an impure brown-red oxide of iron which remains after the distillation of the acid from sulphate of iron. It forms a durable color, but is most used by artists in polishing glass and metals.

Ochres.--The ochres are various earths containing iron in a greater or less degree of oxidation. Venetian red is a coarse ochre of a dark red color. Indian red is an ochre brought from the East Indies, and has a shade inclining to purple. Red ochre is formed from yellow ochre by exposing it to heat. Burnt sienna is made from the raw terra di sienna, by exposure to heat, by which process its color is changed from yellow to red. Bole is a fine clay, colored by oxide of iron, of which there are many varieties, from yellowish red to brown.

Carmine, the most beautiful of all the reds, is an animal substance made from the cochineal insect, or Coccus cacti. It is deposited from a decoction of powdered cochineal in water, to which alum, carbonate of soda, or oxide of tin is added; but the preparation of the finest varieties is kept secret by the manufacturers, and probably depends much upon the delicacy of the manipulations. A fine color is said to be made by adding acetic acid to a solution of carmine in ammonia.

Lakes of various shades are formed from cochineal precipitated by salts of tin, and other agents. Beautiful lakes are also prepared from madder, by a process of Sir H. Englefield, in which the coloring substance is precipitated from an infusion of madder, by adding solutions of alum, and carbonate of potass. The lake called rose pink, is an extract of Brazil wood, mixed with whiting and alum.

Rouge is made from the flowers of the Carthamus tinctorius, or Dyer's saffron, (also called safflower,) by dissolving an alkali in the infusion, and precipitating the coloring matter by lemon juice. It is very fugacious. Under the same name other pigments are also used.

YELLOWS.--Gamboge is the concrete juice of a tree growing in the East Indies, (Stalagmitis cambogioides.) It is externally of a dull orange color, but becomes of a bright yellow, when wet, or thinly spread upon a white surface. It is partially soluble in water and alcohol, and is chiefly used in water colors.

Orpiment is a sulphuret (sesquisulphuret) of arsenic. The paint called king's yellow, is made from this substance, or from its constituents. It is a brilliant, but not very durable color, and its use is in some cases dangerous to the health.

Naples yellow is prepared by exposing lead and antimony with potass, to the heat of a reverberatory furnace. It stands tolerably well, but turns black upon the contact of iron. A native pigment of this kind is also obtained from a species of lava.

Yellow ochre is a native earth, the finer particles of which, are separated by washing, as in similar substances. Although not very bright, its cheapness and durability have caused it to be extensively used.

Terra di sienna is also an ochre, of a deeper and brighter yellow than most of the others.

Massicot or masticot, is the protoxide of lead, prepared by collecting the gray film which floats upon the surface of melted lead, and exposing it to heat and air until it assumes a yellow color.

Chrome yellow is a chromate of lead. It is precipitated by adding chromate of potass in solution, to a solution of nitrate, or acetate, of lead. It forms one of the most brilliant yellows, and is extensively manufactured in this country, from the chromate of iron found near Baltimore.

Turpeth mineral is a subsulphate of mercury, or rather a sub-bisulphate. It is a pale yellow, and moderately durable.

Patent mineral yellow is a fused muriate of lead, made by decomposing common salt by means of litharge, triturating the product with water, washing away the soda, and drying and fusing the muriate.

Dutch pink is a cheap color used by paper stainers, composed of whiting colored by a decoction of dyers' wood, quercitron, or French berries, with alum.

GREENS.--Verdigris is an acetate of copper, or, strictly, an impure acetate of the peroxide of copper. It is manufactured in the south of France, by covering plates of copper with the refuse of the grapes, after making wine. It may also be formed by exposing copper to the vapor of vinegar.

Terra verte is a native blue-green ochre. It is semitransparent and durable, but not very bright.

Brunswick green, called also mineral green, is an ammoniaco-muriate of copper, much used for paper hangings, and occasionally in oil painting.

Sap green is the inspissated juice of the berries of the buckthorn, (Rhamnus catharticus.) It is semitransparent, and chiefly used in water colors.

Many of the greens in common use are compound colors, made by the admixture of blue with yellow.

BROWNS.--Umber is a light brown ochre. Burnt umber is the same substance, having its color darkened by exposure to heat. It is durable in both states.

Spanish brown is a coarse durable ochre, its color inclining to red.

Bistre is prepared from common soot of wood, by pulverizing and washing. The soot of the beech is said to afford the best.

Asphaltum is prepared from the bituminious substance of that name. When dissolved in oil of turpentine, it is semitransparent, and is used as a glaze.

Ox gall consists of the biliary concretions found in the gall-bladder of cattle. It is not soluble in water or alcohol, but dissolves readily in a solution of potass. It is of a yellowish brown, and is much valued for the brightness and permanence of its tint. The liquid ox gall is used by painters to facilitate the laying on of colors.

BLACKS.--Lamp black is a light carbonaceous substance, thrown off during the combustion of resinous and oily substances. The chips of fir and pine trees are burnt under tents, to the inside of which the lamp black adheres.

Frankfort black.--This is a charcoal made from the lees of wine. It is used in the ink of copperplate printers.

Ivory black, called also Cologne black, is made from the shavings and dust of ivory, heated in covered iron pots. Various other carbonaceous colors are made from cork, vine twigs, peach stones, &c, converted into charcoal.

Indian ink is said to be made from different sorts of lamp black, mixed with water and glue. The black is obtained from the smoke of oil, of fir wood, or of horse chestnuts. A solution of lac with borax in water, is said to be the vehicle of the lamp black in some kinds.

Sepia is the black liquid obtained from the cuttle fish. It is of a viscid consistence, and is preserved by drying it upon saucers or shells.

WHITES.--White lead, formerly ceruse, is a carbonate of lead, prepared by exposing coils of sheet lead, in earthen pots, to the vapor of vinegar for several weeks. It is sometimes also formed by precipitation with carbonic acid from a solution of acetate of lead in water.

Flake white consists of the densest and thickest scales, which are separated in making the foregoing article from sheet lead. It is very pure, whereas the white lead of commerce is adulterated with chalk.

Pearl white is the subnitrate of bismuth, formerly called magistery of bismuth, precipitated by water from its solution in nitric acid. It has been used as a cosmetic, but grows yellow by age and light.

Whiting.--Common chalk, separated, in the form of an impalpable powder, by washing. Blanc de Troyes is similar to whiting.

Zinc white is the oxide of zinc. It does not work easily, but is thought very durable. Various marls and clays from Bougival, Rouen, Moudon, &c, are used for white pigments.

Preparation.--Coloring substances, before being used in painting, require to be reduced to a state of extreme fineness. For this purpose, they are ground in a color-mill, and levigated with a stone and muller In many cases, colors, which are insoluble in water, are separated by washing, the water being first made turbid with the coloring substance, and left to stand a short time, till the coarser particles have subsided. The upper part of the fluid, with the finer particles in suspension, is then poured off, and the second deposit which takes place from this is sufficiently fine for mixing. When a greater degree of tenuity is required, the washing is repeated.

Application.--As colors are first prepared for use by simply reducing them to powder, it is necessary that some tenacious fluid should be introduced to make their particles adhere to the surface on which they are spread. To effect this end, various fluids are employed, and the difference of the material used, with the method of employing it, has given rise to the modes of painting in water, in oil, in fresco, in distemper, &c.

Crayons.--The most simple mode of applying colors is by the use of crayons. Crayons are cylinders, or sticks, of dry colors, cemented into a friable mass like chalk, by the assistance of gum or size, and sometimes of clay. They are used by simply rubbing them upon paper, and afterwards blending and softening the shade by means of a stump, or small roll of leather, or paper. But drawings in crayons and chalks, have always the disadvantage, that they do not adhere to the paper, but are rubbed off, and defaced, with the slightest attrition. In this state, they can be safely kept and examined only in frames under glass. Various modes have been practised for fixing crayon drawings upon paper, so as not to be liable to defacement. Among other means, this end may be effected by brushing the back of the paper with a strong solution of isinglass, or by passing the drawing through a powerful press, in contact with a moist paper.

Water Colors.--The most common mode of painting on paper, is by the use of water colors. These are formed into hard cakes or lozenges, with a larger quantity of gum than is employed for crayons. When used, they are rubbed down with water upon glass, or a glazed surface, and applied while wet with a camels' hair pencil. The gum with which they are mixed, causes them to adhere so closely to the paper that they cannot be rubbed off.

Distemper.--Painting in distemper is used for works to be executed upon a larger scale, such as stage scenery, the walls of apartments, &c. The colors are used in the form of powder, and are mixed with water rendered glutinous by size, or other solutions of animal glue. The mixture requires, in many cases, to be used warm, as the solution becomes stiff upon cooling. Skimmed milk also serves as a vehicle for painting in distemper, and its tenacity is increased by adding small portions of lime, and of linseed or poppy oil. The mixture dries speedily, the oil being converted into a soap by the lime.[A] Distemper in badigeon is employed by the French to restore the original color to stone walls which have become brown by time; and consists in washing them with powder of the same kind of stone, properly mixed. Chipolin is a varnished distemper.

[A] This method is highly recommended by Tingry, who gives the following recipe. Skimmed milk, four pounds; lime, newly slaked, six ounces; linseed, nut, or poppy oil, four ounces; Spanish white, (white clay,) three pounds.

Paper staining.--Paper hangings, for the walls of rooms, were originally introduced in China, and some of the more elaborate kinds are printed by hand. But the method, now almost universally employed, consists in printing by blocks. The ground color is first laid upon the paper with a brush, after which, the figures are stamped by wooden blocks engraved for the purpose. Each color requires a separate block, and these are used in succession, the workmen being guided by a pin in placing the blocks, so as to prevent the colors from interfering. The glazing of the paper is performed by a smooth brass roller.

Flock paper, commonly called cloth paper, is made by printing the figures with an adhesive liquid, commonly linseed oil boiled or litharge. The surface is then covered with the flocks, or woollen dust, which is produced in manufactories by the shearing of woollen cloths, and which is dyed of the requisite colors. After being agitated in contact with the paper, the flocks are shaken off, leaving a coating, resembling cloth, upon the adhesive surface of the figures.

Fresco.--Paintings in fresco are executed upon walls recently plastered, before they have become dry. The coloring substance, mixed with water, being applied while the wall is wet, sinks in and incorporates itself with the grain of the mortar, so as to become very durable. When a wall is to be done in fresco, it is covered with a coating of stucco or fine mortar, which is applied in successive portions, no more being put on at once than can be painted before it is dry. This mode of finishing by piecemeal, renders it necessary that the artist should have his whole design either upon paper, or thoroughly digested in his mind, before he begins. The drawings which are executed upon large paper to serve as patterns for fresco paintings, are called cartoons. They are transferred to the walls by puncturing through the outlines with a sharp point.[A] Many of the greatest works of the most eminent Italian masters are executed in fresco, upon the walls and ceilings of the different churches and cathedrals.

Encaustic Painting.--The ancients made use of a mode denominated encaustic painting, the knowledge of which, at the present day is lost. From the writings of Pliny, it appears that the material with which the colors were incorporated, was wax, and that this was applied by the assistance of heat. It is represented as having been very brilliant and durable, though no specimens of it remain at this day. The principal paintings which have been discovered upon the walls at Herculaneum and Pompeii, appear to have been done in fresco.

Oil Painting.--Painting in oil, which, on many accounts, has a great superiority over other methods, was first applied to the execution of designs about the year 1410, by John Van Eyck, in Flanders. The oils, used for painting, must be of the class denominated drying oils. Of these, linseed oil is the kind most commonly employed, and its tendency to dry is increased by its being boiled. Its color renders it sometimes injurious to light tints; so that in delicate pieces it is better to employ nut oil, or poppy oil, which are nearly transparent, and do not turn dark in drying. The drying of paint is owing, not so much to evaporation, as to a chemical combination of the oil with the pigment, especially when the latter is a metallic oxide, or other substance, having a direct affinity for the oil. The oxygen of the atmosphere appears also to enter into this combination. The drying will be frustrated, if a small quantity of any fat oil be present. Hence, in painting old surfaces, which have been exposed to contract any greasiness, it is necessary first carefully to cleanse them, or to wash them with lime in water, or with some alkaline solution, which combines with the oil. The latter method is practised by house painters.

[A] Cartoons are also used as patterns in tapestry and mosaic.

Oil paintings of designs are executed either on canvass, on wood, or on copper. When the colors used are chiefly of the kind denominated body colors, each successive layer conceals those beneath it, so that the work may be heightened, amended, or altered, at pleasure, during any stage of the process. Paintings in oil are very durable, and acquire a mellowness from age which improves rather than injures their effect, provided permanent colors have been used.

Painting in the large way, with uniform colors, mixed in oil, is employed, not so much for ornament, as for the protection of perishable substances from decay. Thus wood may be preserved from decomposition, and metals from oxidation, for an indefinite time, by keeping them covered with a thick coating of paint, which is imperv-ous to air and moisture.

Varnishing.--The name of varnishes is given to certain compounds, chiefly solutions of resinous substances, which, after being spread over surfaces, and dried, possess the qualities of hardness, brilliancy, and transparency. They are employed to give lustre and smoothness to painted surfaces, and to defend them from the action of the air.

The principal substances which form the basis of varnishes, are copal, mastic, animé, sandarac, lac, benzoin, amber, and asphaltum. Of these, copal is a hard, shining, transparent resin, of a light citron color, originally brought from Spanish America, and erroneously considered as the product of the Rhus copallinum.[A] True copal is soluble in oil, but is difficult of solution in alcohol. It is commonly made into varnish by dissolving it in hot linseed oil, rendered drying by quicklime, and diluting the solution with oil of turpentine. By mixture with camphor, it becomes soluble in alcohol, or in oil of turpentine. Mastic is a resinous substance, in the form of tears, of a pale yellow color, brittle, and semitransparent. It comes from the Levant, and is produced by the Pistacia lentiscus. A greater part of it is soluble in alcohol and in oil of turpentine. Animé is brought from Spanish America, and is said to be obtained from the Hymenæea courbaril. It resembles copal very much in its appearance, but is easily soluble in alcohol, while copal is not. It is often sold under the name of copal. Sandarac is the resin of the Thuya articulata, which grows in Barbary. It resembles mastic, but is rather more transparent and brittle. When chewed, it crumbles to powder, whereas mastic softens in the mouth. It is soluble in alcohol and oil. Lac is deposited on certain trees in the East Indies, by an insect called Coccus lacca. The substance in its natural state, incrusting the twigs, is called stick lac; when broken off, and boiled in water till it loses its red color, it is termed seed lac, and when melted and reduced to a thin crust, it is called shell lac. Stick lac has a deep red color, and yields to water a red substance which is used as a dye. Lac is soluble in alcohol. Benzoin is the product of the Styrax benzoe, a tree growing in Sumatra. It is a solid, brittle substance, in yellowish white tears, joined together by a brown substance, and is sometimes wholly brown. It is a balsam, and affords benzoic acid. Amber and asphaltum are mineral substances, already mentioned in the second chapter.

Varnishes are divided into three kinds, according to the menstruum in which the resinous substance is dissolved. These are spirit varnishes, in which the solvent is alcohol; essential varnishes, in which a volatile oil, commonly oil of turpentine, is used; and oil varnishes, which consist of a resin dissolved in a drying oil. Some vegetable juices may be applied in their liquid state. Thus the viscid juice of the Rhus vernix affords the celebrated black varnish used in Japan. The same shrub, which grows in this country, affords a whitish juice, which, upon boiling, yields a strong, glossy, black varnish.[1]

[A] The Rhus copallinum is a common shrub in the United States, and is not known to produce any substance resembling copal. According to Hernandez, the copal of Spanish America is obtained from various trees. I am informed that the copal used in this country comes almost wholly from the East Indies. It is probably the produce of the Elæocarpus copalifera.

An elastic varnish may be made by dissolving caoutchouc in linseed oil and oil of turpentine; but this preparation dries slowly. Besides the solvents mentioned in the first chapter of this work, it is found that the naphtha of coal tar dissolves caoutchouc readily, and on drying leaves its properties unaltered.[2]

Japanning.--Japanning is the art of varnishing in colors, and is therefore a species of painting. It is most easily executed upon wood and metal, or such other substances as retain a determinate form, and are capable of sustaining the operation of drying the varnish. Paper and leather, when wrought into forms in which they remain stretched, stiff, or inflexible, are common subjects for japanning.

The article to be japanned is first brushed over with two or three coats of seed lac varnish, to form the priming. It is then covered with varnish previously mixed with a pigment of the tint desired. This is called the ground color; and if the subject is to exhibit a design, the objects are painted upon it, in colors mixed with varnish, and used in the same manner as for oil painting. The whole is then covered with additional coats of transparent varnish, and all that remains to be done, is to dry and polish it.

Japanning requires to be executed in warm apartments, and the articles are warmed before the varnish is applied to them. One coat of varnish, also, must be dry before another is laid on. Ovens are employed to hasten the drying of the work.

[1] See American Medical Botany, vol. i. p. 101. The shrub is poisonous to many persons.

[2] Annals of Philosophy, vol. xii.

The same pigments which are employed in oil or water, answer also in varnish. For painting figures, shell lac varnish is considered best, and easiest to work; it is therefore employed in most cases where its color permits. For the lightest colors, mastic varnish is employed, unless the fineness of the work admits the use of copal dissolved in alcohol.

Polishing.--Pictures, and other subjects, to which only a thin coat or two of varnish is given, are generally left to the polish which the varnish naturally possesses, or are brightened only by rubbing them with a woollen cloth when dry. But whenever several coats of varnish or japan are laid on, a more glossy surface can be produced, by means similar to those which are used to polish metals; the surface having first been suffered to become completely dry and hard. Where the coat of varnish is very thick, the surface is first rubbed with pumice stone and oil, till it becomes uniformly smooth; the pumice having been previously reduced to a smooth, flat face, by rubbing it on freestone. The japanned or varnished surface may afterwards be rubbed with pumice reduced to an impalpable powder, the workman using oil and leather to lay on the powder. The finishing may be given by oil and a piece of woollen only.

Where the varnish is thinner, and of a more delicate nature, it may be rubbed with tripoli, or rotten stone, in fine powder, finishing with oil as before. Where the ground is white, putty, or Spanish white, finely washed, may be used instead of rotten stone, of which the color might have some tendency to injure the ground.

Lackering.--Lackering consists in the application of transparent varnishes to metals, to prevent their tarnishing, or to give them a more agreeable color. When the color of the metal to be lackered is to be changed, the varnish is tinged with some coloring matter; but where preservation from rust, or tarnish, is the sole object, any of the transparent varnishes will answer, the best and hardest being used where the greatest durability is required. Shell lac is the most common basis of the varnishes used in lackering. An imitation of gilding is effected by covering the surface of tin or lead with a clear varnish tinged with annotto, turmeric, or gamboge. The Chinese gilt paper appears to be made in this manner.

Gilding.--The process of gilding on metals, described in a former chapter, depends on a chemical union, or alloy, between the gold and the metal to which it is applied. But gilding, as it is commonly performed upon wood, leather, &c, is a mechanical process, and consists in cementing gold leaf upon surfaces, for which it has no affinity. In common oil gilding, the surface to be gilt is covered with an adhesive coating of paint or gold size, composed of yellow ochre ground in oil. When this is partially dried, so as to feel adhesive, the gold leaf is laid upon it and pressed down with cotton wool. When the whole surface is covered, it is left to dry, and the superfluous gold leaf brushed off. In burnish gilding, the surface to be gilt is first covered with a mixture of whiting and size, prepared by boiling shreds of parchment or skins, in water. This is rubbed smooth, and covered with a gilding size containing a little ochre or Armenian hole. This is suffered to dry, and is rubbed smooth with a linen rag. The gilding is then performed by moistening successively the parts of the sized surface with water, and applying the gold leaf before it becomes dry. When the work has become firm, it is burnished by rubbing it with a hard, polished substance, such as agate, dog's tooth, or steel.

Gilding on leather and on paper may be performed by applying gold leaf with gum arabic or size. The edges of paper and of books are gilded with a size composed of whites of eggs, beaten with three or four times their quantity of water, and mixed with a little Armenian bole. Bookbinders gild the leather of books by coating it two or three times with whites of eggs, and suffering it to dry. A minute quantity of tallow is then rubbed on, and the gold leaf laid loosely upon the surface. The stamps and letters are cut in brass; or printing types are used. These are moderately heated, as much as the leather will bear, and are then pressed upon the gold leaf, by which a portion of gold corresponding to the letters is made to adhere; after which, the superfluous gold leaf is brushed off.

Shell gold is prepared by grinding up gold leaf with honey until it is completely subdivided; the honey is then washed away with water, and the gold powder mixed with gum water or some other adhesive fluid. It is usually kept for use on shells, and is applied with a pencil or brush in the manner of common painting.

Photography.--This recent discovery, called also heliography, and photogenic drawing, has excited much interest among artists and men of science. The instrument or apparatus employed, has been called the Daguerreotype from its inventor, M. Daguerre, of Paris.

It has long been known that the sun's rays have the power of decomposing certain chemical compounds, in a very short time, and that this effect is produced most rapidly by the violet rays, and by rays which exist just beyond them in the prismatic spectrum, and that this property gradually diminishes as we advance to the red ray, at which it seems wholly wanting. Among the substances most sensitive to the chemical action of light, is the chloride of silver. It is at first perfectly white, but if exposed to the direct solar rays for a few minutes, it becomes violet, and at length almost black. The same effect is produced, more slowly, by exposure to indirect or diffused daylight.

If a substance of definite form, for instance, the leaf of a plant, be laid close upon a sheet of paper, previously prepared by coating it with a substance chemically sensible to light, and the whole be then exposed to the sun's rays, the surface of the paper will turn black, with the exception of the part covered by the leaf, which, being protected from the rays, will remain white, or nearly so, exhibiting the exact outline of the leaf. But as the leaf is not opaque, but partially transparent, some light will penetrate through its cells and pores, producing slight shades on the white surface beneath. These shades, necessarily corresponding to the veins and cells of the leaf, will produce a beautifully shadowed and reticulated appearance, corresponding exactly to that of the leaf itself.

It is well known that in the instrument called the camera obscura, a reduced image of natural objects is made to fall in shadow upon a plane surface. A desire has been excited among artists to preserve this image, by receiving it on a surface made chemically sensible to light, so that it might retain the difference of shade between the space covered by the image, and the unoccupied ground. Various experimenters, as M. Niepce in France, Mr. Talbot and others in England, have approximated towards this result, but complete success has only been attained by M. Daguerre, to whom the French Government has recently presented a reward, and whose method has been thus described, by M. Arago, before the Academy.

A copper sheet, plated with silver, well cleaned with diluted nitric acid, is exposed to the vapor of iodine, which forms the first coating, which is very thin, as it does not exceed the millionth part of a metre in thickness. There are certain indispensable precautions necessary to render this coating uniform, the chief of which is, the using of a rim of metal round the sheet. The sheet, thus prepared, is placed in the camera obscura, where it is allowed to remain from eight to ten minutes. It is then taken out, but the most experienced eye can detect no trace of the drawing. The sheet is now exposed to the vapor of mercury, and when it has been heated to a temperature of sixty degrees of Reaumur, or one hundred and sixty-seven Fahrenheit, the drawings come forth as if by enchantment. One singular fact in this process is, that the sheet, when exposed to the action of the vapor, must be inclined, for if it were placed in a direct position over the vapor, the results would be less satisfactory. The angle used is forty-five degrees.

After these three operations, for the completion of the process, the plate must be plunged into a solution of hyposulphite of soda. This solution acts most strongly on the parts which have been uninfluenced by light; the reverse of the mercurial vapor, which attacks exclusively that portion which has been acted on by the rays of light. From this it might, perhaps, be imagined, that the lights are formed by the amalgamation of the silver with mercury, and the shadows by the sulphuret of silver formed by the hyposulphite. M. Arago, however, formally declared the positive inability of the combined wisdom of physical, chemical, and optical science, to offer any theory of these delicate and complicated operations, which might be even tolerably rational and satisfactory.

The picture now produced is washed in distilled water, to give it that stability which is necessary to its bearing exposure to light without undergoing any further change.

After his statement of the details of M. Daguerre's discovery, M. Arago proceeded to speculate upon the improvements of which this beautiful application of optics was capable. He adverted to M. Daguerre's hopes of discovering some further method of fixing not merely the images of things, but also of their colors; a hope based upon the fact, that, in the experiments which have been made with the solar spectrum, blue color has been seen to result from blue rays, orange color from orange, and so on with the others. Sir John Herschel is sure that the red ray alone is without action. The question arose, too, whether it will be possible to take portraits by this method. M. Arago was disposed to answer in the affirmative. A serious difficulty, however, presented itself: entire absence of motion on the part of the object is essential to the success of the operation, and this is impossible to be obtained from any face exposed to the influence of so intense a light. M. Daguerre, however, believes that the interposition of a blue glass would in no way interfere with the action of the light on the prepared plate, while it would protect the sitter sufficiently from the action of the light. The head could be easily fixed by means of supporting apparatus. Another more important desideratum is, the means of rendering the picture unalterable by friction. The substance of the pictures executed by the Daguerreotype is, in fact, so little solid--is so slightly deposited on the surface of the metallic plate--that the least friction destroys it, like a drawing in chalk: at present, it is necessary to cover it with glass.[A]

[A] A varnish made of a solution of dextrine, protects the surface, but impairs the brilliancy of the picture.

From his numerous experiments on the action of light on different substances, M. Daguerre has drawn the conclusion, that the sun is not equally powerful at all times of the day, even at those instants when his height is the same above the horizon. Thus, more satisfactory results are obtained at six in the morning than at six in the afternoon. From this, too, it is evident, that the Daguerreotype is an instrument of exquisite sensibility for measuring the different intensities of light, a subject which has hitherto been one of the most difficult problems in Natural Philosophy. It is easy enough to measure the difference in intensity between two lights viewed simultaneously, but when it is desired to compare daylight with a light produced in the night--that of the sun with that of the moon, for example--the results obtained have had no precision. The preparation of M. Daguerre is influenced even by the light of the moon, to which all the preparations hitherto tried were insensible, even when the rays were concentrated by a powerful lens.

In physics, M. Arago indicated some of the more immediate applications of the Daguerreotype, independently of those which he had already mentioned in photometry. He instanced some of the most complex phenomena exhibited by the solar spectrum. We know, for example, that the different colored rays are separated by black transversal lines, indicating the absence of these rays at certain parts; and the question arises, whether there are also similar interruptions in the continuity of the chemical rays. M. Arago proposes, as a simple solution of this question, to expose one of M. Daguerre's prepared plates to the action of a spectrum; an experiment which would prove whether the action of these rays is continuous, or interrupted by blank spaces.

The degree of perfection which attends the process of photography exceeds that of any drawing, and is thus described by a witness.

"M. Daguerre puts a magnifying glass in our hand. We then see the minutest folds of drapery, the lines of a landscape, invisible to the naked eye. In the mass of buildings, accessories of all kinds, imperceptible accidents, of which the view of Paris from the Pont des Arts is composed, we distinguish the smallest details, we count the stones of the pavement, we see the moisture produced by rain, we read the sign of a shop. Every thread of the luminous tissue has passed from the object to the surface retaining it. The impression of the image takes place with greater or less rapidity, according to the intensity of the light; it is produced quicker at noon than in the morning or evening, in summer than in winter."

It has been observed, that the cost of the plate must necessarily be considerable, and the chemical process requires nicety and skill; so that the expense of the photographic pictures will not be so trifling as might be supposed, especially when accidental failures are taken into account. By this process, it is to be borne in mind, the picture appears on the plate as it does on the camera, that is, with its forms and shadows painted dark on a white ground. In the simpler process, invented by Mr. Talbot, by which the solar rays act on a prepared paper, called photogenic, the light and shades of the real objects are reversed, and the picture is painted white on a dark ground. Mr. Talbot's method of preparing photogenic or sensitive paper, consists in washing fine writing paper over, first with a solution of nitrate of silver, then with bromide of potassium, and afterwards with nitrate of silver again; drying it at the fire after each operation. He also imitates etching on copperplate, by smearing over a piece of glass with a solution of resin in turpentine, and blackening it by the smoke of a candle: on this ground, the design is traced with the point of an etching needle, and the sensitive paper being placed behind the glass exposed to the sun, the rays of light, passing through the transparent lines, act upon the paper, and leave the design imprinted in a brown hue. The experiment can be repeated as often as may be desired. This last-mentioned process, however, is but printing by sunlight from etching on glass: it is curious enough, but far inferior to the perfection of M. Daguerre's process, by which the external picture is depicted in miniature, light for light, and shade for shade, to the minutest gradation of each. Color alone is wanting in the results of this remarkable process.


The processes considered in the previous part of this chapter, are used to produce an external modification of color, and consist in mechanically covering the surfaces upon which they are applied. The remaining division includes those arts which depend more exclusively upon chemical processes, and which, by operating on the internal texture of bodies, produce a total and intrinsic change of color. Of this kind are the arts of bleaching, dyeing, and calico printing. The operations, however, which belong to these arts, are too extensive to be considered in all their details in this place.

Bleaching.--Bleaching is the process by which fibrous textures, such as linen, cotton, silk, &c., are deprived of their color, and rendered white. The coloring matter, which is inherent in vegetable fibres, appears to be of a resinous character, and the effect of the operation of bleaching is to dissolve, or discharge it. In manufactories of linen and cotton goods, the yarn or cloth passes through a number of successive processes, the principal of which are the steeping, in which the goods are fermented in an acescent liquid at a temperature of about one hundred degrees, Fahrenheit--the bucking and boiling, in which a hot alkaline ley is made to percolate through them for some time--the souring, performed with diluted sulphuric acid--the bleaching with chlorine, in which the stuff is exposed to the action of some compound of that substance, usually chloride of lime, called bleaching salt. Various mechanical operations, washings, and repetitions of the processes, are commonly practised to complete the discharge of the color. Formerly the process of bleaching was very tedious, and was effected by alkaline leys and by exposure to the sun and air, with frequent irrigations, for many weeks. The discovery of the bleaching power of chlorine has greatly abridged and simplified the process.

Chemists explain the effect of chlorine in bleaching,[1] by supposing that it unites with the hydrogen of the coloring matter, and forms muriatic acid, which again acts upon the color in its altered state. The acid may be detected in the altered coloring matter. In bleaching, which is performed by exposure to the air and moisture, it is supposed that oxygen combines with the coloring matter, and renders a portion of it more easy of solution, during the other parts of the process.

The fibres of wool and silk are not bleached by chlorine, but, after being deprived of the saponaceous or gummy matter, which adheres to them, are exposed to the fumes of burning sulphur to discharge their color.

Dyeing.--The art of dyeing consists in impregnating cloths and other flexible fabrics with coloring substances, in such a manner, that the acquired color may remain permanent under the common exposures to which the stuffs may be liable. It is effected by producing a chemical union between the material to be dyed and the coloring matter. It is found that different materials not only possess different attractions for dye stuffs, but that they absorb the coloring matter in different proportions. Wool appears in this respect to have the greatest attraction for coloring substances; silk comes next to it, then cotton, and, lastly, hemp and flax.

Mordants.--The coloring substances used in dyeing have been divided by Dr. Bancroft into substantive and adjective colors. Substantive colors are those which communicate their tint immediately to the material to be dyed, without the aid of any third substance. Adjective colors require the intervention of a third substance, which possesses a joint attraction for the coloring matter and the stuff to be dyed. The substance capable of thus fixing the color, is called a mordant, and by Mr. Henry, a basis.

The agents, which are capable of acting in some way as mordants, are very numerous, including many oxides and salts. But those which are principally employed in practice, are the acetate of alumina, the sulphate or acetate of iron, and the muriate of tin. The substance to be dyed is first impregnated with the mordant, and then passed through a solution of the coloring matter. The mordant fixes the color, and, in many cases, alters or improves and heightens its tint.

[1] Gay-Lussac, Cours de Chimie, L'ec. 30, p. 2.--Ure's Notes to Berthollet, ii. 344.

Dyes.--The coloring substances, capable of being used as dyes, are very numerous; but a few of the most important have, in practice, taken precedence of the rest. Indigo, madder, quercitron, and some of the woods, are consumed in vast quantities by dyers, and are capable of producing an indefinite variety of tints, under the action of different mordants. They are somewhat differently treated, according as the substance to be dyed is of wool, silk, or cotton.

Blue Dyes.--Indigo is the chief substance employed for giving the blue dye. The best indigo is obtained from a plant cultivated in warm climates, the Indigofera tinctoria. The plant is cut a short time before its flowering, and put into large vats covered with water, when fermentation spontaneously ensues, during which the indigo subsides in the form of a pulverulent, pulpy matter. Its color is at first green, but, by exposure to the air, it absorbs oxygen and becomes blue.

Indigo is a light, brittle substance, of a deep blue color, and without either taste or odor. At five hundred and fifty degrees Fahrenheit, it sublimes, forming a violet vapor with a tint of red, and condensing into long, flat, acicular crystals, which appear red by reflected, and blue by transmitted light. The process of subliming indigo is one of considerable delicacy, owing to the circumstance that the temperature at which it sublimes, is very near that at which it is decomposed. Indigo, in its dry state, may be preserved without change; but when kept under water, it is gradually decomposed. It is quite insoluble in water and alcohol, and is attacked by the alkalies in a partial manner. Its only proper solvent is concentrated sulphuric acid. When indigo is put into this acid, a yellow solution is at first formed, which, after a few hours, acquires a deep blue color. If the indigo is pure, sulphurous acid is not generated, nor is the acid decomposed; but the indigo undergoes a change, for it is rendered soluble in water. To the indigo thus modified, Mr. Crum has applied the name cerulin, and he regards it as a compound of one atom of indigo and four atoms of water. This solution, properly diluted with water, is employed by dyers for forming what is called the Saxon blue. Mr. Crum has also described another compound of indigo and water, under the name of Phoenecin, because it acquires a purple color on the addition of a salt. It appears to consist of one atom of indigo and two atoms of water.

When indigo, suspended in water, is brought into contact with certain deoxidizing agents, it is deprived of oxygen, becomes green, and is rendered soluble in water, and still more in the alkalies. This effect is produced, for example, by sulphuretted hydrogen, by the hydrosulphuret of ammonia, by the protoxide of iron, precipitated by lime or potass, or by a solution of the sulphuret of arsenic in potass. On dipping cloth into a solution of deoxidized indigo, it receives a green tint, which becomes blue by exposure to the air. This is the usual method of dyeing blue by means of indigo, a color which adheres permanently to cloth without the intervention of a basis.

Woad is prepared from the leaves of the Isatis tinctoria, a plant cultivated in Europe. Gay-Lussac, and others, consider it chemically as a species of indigo. It is prepared by grinding, and several processes of fermentation. Cloth dyed in woad liquor, is at first green, but turns blue on exposure to the air, in the same manner which takes place with indigo.

Red Dyes.--The chief substances which are employed for giving a red dye, are madder, cochineal, archil, Brazil wood, logwood, and safflower, all of which are adjective colors.

Madder, which is one of the most valuable drugs in the art of dyeing, is the root of the Rubia tinctorum, a plant extensively cultivated in Europe, and particularly in Holland. It is properly classed with red dyes, but, by the use of different mordants, it is made to produce every shade of red, purple, and even black. In calico printing, a piece may be stamped with several mordants, which are bases of different colors; and upon immersing it in a madder bath, as many colors will appear as there are mordants used. The quality of madder is said to be improved by age, provided it is kept packed in casks which exclude the air. Its quality is also affected by the mode of cultivating and curing it, and the judgement which is used in separating the samples.

Cochineal is obtained from an insect, already mentioned, which feeds upon the leaves of several species of the cactus, and which is supposed to derive this coloring matter from its food. It is very soluble in water, and is fixed on cloth by means of alumina or the oxide of tin. Its natural color is crimson; but when the bitartrate of potass is added to the solution, it yields a rich scarlet dye. Cochineal, according to Pelletier and Caventou, is composed of, 1. Carminium, which is the name given to the coloring matter. 2. A peculiar animal matter. 3. A fatty substance. 4. Salts of lime and potass.

Archil.--The dye called archil, is obtained from a kind of lichen, (Lichen roccella) which grows chiefly in the Canary Islands, and is employed by the Dutch in forming the blue pigment called litmus or turnsol. The coloring ingredient of litmus is a compound of the red coloring matter of the lichen and an alkali; and hence, on the addition of an acid, the coloring matter is set free, and the red tint of the plant is restored. Litmus is not only used as a dye, but is employed by chemists for detecting the presence of a free acid.

Logwood is a dense, heavy wood, derived from the Hæmotoxylum Campechianum, which grows in the tropical parts of America. A decoction made from this wood, is of a fine red, inclining a little to violet or purple. This, if left to itself, becomes in time yellowish, and at length black. The violet color of logwood is fixed by alum, and a blue is obtained from it by verdigris. But the great consumption of logwood is for blacks, to which it gives a peculiar depth, and velvety lustre. The coloring principle of logwood has been procured in a separate state by M. Chevreul, who has applied to it the name of hematin. It is obtained in crystals, by digesting the aqueous extract of logwood in alcohol, and allowing the alcoholic solution to evaporate spontaneously.

Brazil wood is the heart, or central part of the Cæsalpinia echinata, a large tree of Brazil. It produces very lively and beautiful red tints, with solutions of alumina and tin, but they are deficient in permanency. Sappan wood, brought from the East Indies, and Nicaragua wood, or Peachwood, from Central America, are also said to be species of Cæsalpinia, and resemble Brazil wood in their properties, but yield a smaller amount of coloring matter. Braziletto and Camwood are among the poorest of the red dyes.

Safflower is the dried flowers of the Carthamus tinctorius, and affords a bright but fugitive red. See Rouge.

Yellow Dyes.--The chief yellow dyes are the quercitron bark, turmeric, hickory, weld, fustic, and saffron. They are all adjective colors.

Quercitron bark, which is one of the most important of the yellow dyes, is an extract made from the bark of the Quercus tinctoria, or common black oak of the United States, and was introduced into notice by Dr. Bancroft. With a basis of alumina, the decoction of this bark gives a bright yellow dye. With the oxide of tin, it communicates a variety of tints, which may be made to vary from a pale lemon color to deep orange. With the oxide of iron, it gives a drab color.

Hickory.--Several species of American walnut or hickory, particularly the Juglans, or Carya alba, yield a yellow dye from their bark, leaves, and rinds, resembling quercitron, but less abundant in quantity.

Weld is derived from a European plant, Reseda luteola. When fixed with a basis of alum, it gives a lively and permanent yellow.

Fustic is the wood of the Morus tinctoria, a tree of the West Indies. It affords, with an aluminous basis, a less brilliant, but more durable yellow, than the preceding articles. It is also employed to produce certain greens and drab colors.

Annotto, otherwise called Rocou, is a soft substance prepared from the seeds of the Bixa orellana, a shrub of tropical America. The coloring matter is combined with a resin which renders it difficult of solution in water. An alkali facilitates the solution and improves the color.

Turmeric is the root of the Curcuma longa, a native of the East Indies. Paper, stained with a decoction of this substance, constitutes the turmeric or curcuma paper employed by chemists as a test of free alkali; by the action of which it receives a brown stain.

Saffron.--The coloring ingredient of saffron (Crocus sativus) is soluble in water and alcohol, has a bright yellow color, is rendered blue and then lilac by sulphuric acid, and receives a green tint on the addition of nitric acid. From the great diversity of colors which it is capable of assuming under different circumstances, M. M. Bouillon, Lagrange, and Vogel, have proposed for it the name of Polychroite.

French Berries.--The unripe berries of the Rhamnus infectorius afford a lively but fugitive yellow.

Black Dyes.--The black dye is made of the same ingredients as writing ink, and therefore contains usually a compound of the oxide of iron with gallic acid and tannin. From the addition of logwood and acetate of copper, the black receives a shade of blue.

Galls.--The common nutgall is an excrescence produced upon an Asiatic species of oak, (Quercus infectoria) by the puncture of an insect, a species of cynips. It contains tannin, gallic acid, and, according to Dr. Bancroft, a coloring matter distinct from these. Galls produce a black color with salts of iron, well known as the basis of writing ink.

Maple.--The common red maple of this country, (Acer rubrum,) when applied with the sulphate or acetate of iron, produces, according to Dr. Bancroft, a more intense and perfect black than any of the common vegetable dyes. With the aluminous basis, it produces a lasting cinnamon color, both on wool and cotton. Both the bark and leaves may be used.

Butternut.--The bark of the butternut (Juglans cathartica) affords a durable brown upon cotton with an aluminous basis, and upon wool without any mordant.

By the dexterous combination of the four leading colors, blue, red, yellow, and black, all other shades of color may be procured. Thus green is communicated by forming a blue ground with indigo, and then adding a yellow by means of quercitron bark.

One of the latest improvements in the art of dyeing, consists in the employment of colors derived from the mineral kingdom. Prussian blue, orpiment, chromate of lead, and other mineral compounds, have, by appropriate processes, been made to communicate their colors to different stuffs. An abstract of the processes is given in Ure's notes to Berthollet on dyeing.

Calico Printing.--Calico printing is a combination of the arts of engraving and dyeing, and is used to produce upon woven fabrics, chiefly of cotton, a variety of ornamental combinations, both of figure and color. In this process, the whole fabric is immersed in the dyeing liquid, but it is previously prepared in such a manner, that the dye adheres only to the parts intended for the figure, while it leaves the remaining parts unaltered. In calico printing, adjective colors are most frequently employed. The cloth is prepared by bleaching and other processes, which dispose it to receive the color. It is then printed with the mordant, in a manner similar to that of copperplate printing, except that the figure is engraved upon a cylinder, instead of a plate. The cylinder, in one part of its revolution, becomes charged with the mordant mixed to a proper consistence with starch. The superfluous part of the mordant is then scraped off by a straight steel edge, in contact with which the cylinder revolves, leaving only that part which remains in the lines of the figure. The cloth then passes in forcible contact with the other side of the cylinder, and receives from it a complete impression of the figure in the pale color of the mordant. The cloth is then passed through the coloring bath, in which the parts previously printed, become dyed with the intended color. When it is afterwards exposed, and washed, the color disappears from those parts which are not impregnated with the mordant, but remains permanently fixed to the rest. When additional colors are required, they are printed over the rest with different mordants, suited to the color intended to be produced. This secondary printing is in most instances performed with blocks, engraved in the manner of wood cuts, and applied by hand to the successive parts of the piece.

In some articles, white spots upon a dark ground are produced by covering the parts with wax, tallow, pipe clay, or other materials, which prevent the contact of the color. Sometimes the color is discharged in places, by the application of chlorine. A preparation of one of the salts of copper, applied in spots, or figures, has the effect to oxygenate indigo, so as to render it insoluble, and consequently incapable of dyeing these spots, when the stuff is immersed. To these and similar processes, the name of resist work has been given.

Fast Colors.--The following are the dye stuffs used by the calico printers for producing fast colors.[1] The mordants are thickened with gum, or calcined starch, and applied with the block, cylinder, plates, or otherwise.

1. Black. The cloth is impregnated with acetate of iron (iron liquor) and dyed in a bath of madder and logwood.

2. Purple. The preceding mordant of iron, diluted; with the same dyeing bath.

3. Crimson. The mordant for purple, united with a portion of acetate of alumina, or red mordant, and the above bath.

4. Red. Acetate of alumina is the mordant, and madder is the dye stuff.

5. Pale red of different shades. The preceding mordant diluted with water, and a weak madder bath.

6. Brown or Pompadour. A mixed mordant, containing a somewhat larger proportion of the red than of the black; and the dye of madder.

7. Orange. The red mordant; and a bath first of madder, and then of quercitron.

[1] Ure's Dictionary.

8. Yellow. A strong red mordant; and the quercitron bath, whose temperature should be considerably under the boiling point of water.

9. Blue. Indigo, rendered soluble and greenish-yellow colored, by potash and orpiment. It recovers its blue color, by exposure to air, and thereby also fixes firmly on the cloth. An indigo vat is also made, with that blue substance, diffused in water with quicklime and copperas. These substances are supposed to deoxidize indigo, and at the same time to render it soluble.

Golden-dye. The cloth is immersed alternately in a solution of copperas and lime-water. The protoxide of iron precipitated on the fibre, soon passes, by absorption of amospherical oxygen, into the golden-colored deutoxide.

Buff. The preceding substances, in a more dilute state.

Blue vat, in which white spots are left on a blue ground of cloth, is made, by applying to these points a paste composed of a solution of sulphate of copper and pipe clay; and after they are dried, immersing it stretched on frames for a definite number of minutes, in the yellowish-green vat, of one part of indigo, two of copperas, and two of lime, with water.

Green. Cloth dyed blue, and well washed, is imbued with the aluminous acetate, dried, and subjected to the quercitron bath.

In the above cases, the cloth, after receiving the mordant paste, is dried, and, after some preparation, put into the dyeing vat of copper.

Fugitive Colors.--All these colors are given, by making decoctions of the different coloring woods; and receive the slight degree of fixity they possess, as well as great brilliancy, in consequence of their combination or admixture with the nitro-muriate of tin.

1. Red is frequently made from Brazil and peachwood.

2. Black. A strong extract of galls, and deuto-nitrate of iron.

3. Purple. Extract of logwood and the deuto-nitrate.

4. Yellow. Extract of quercitron bark, or French berries, and the tin solution.

5. Blue. Prussian blue and solution of tin.

Fugitive colors are thickened with gum tragacanth, which leaves the cloth in a softer state than gum senegal; the goods being sometimes sent to market without being washed.

WORKS OF REFERENCE.--TINGRY'S Painter's and Varnisher's Guide, 8vo. translated 1816;--ELMES'S Dictionary of Fine Arts, 8vo. 1826;--JAMES'S Panorama of Science and Art, 2 vols. 8vo. 1816;--BANCROFT on Permanent Colors, 2 vols. 8vo. 1814;--BERTHOLLET, Elements of the Art of Dyeing, translated by Ure, 2 vols. 8vo. 1824; GAY-LUSSAC, Cours de Chimie, 2 vols. 8vo. 1828;--BRANDE'S Chemistry, 1820;--TURNER'S Chemistry, 1828;--PARKE'S Chemical Essays, 1823;--URE'S Dictionary;--also Philosophy of Manufactures, by do. 8vo. 1835;--VITALIS, Cours élémentaire de teinture, 1823.

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