Cyclopedia of Painting/Colors
COLORS.
Blacks. Lamp black is the soot produced by burning oil, resin, small coal, resinous woods, coal tar or tallow. It is in the state of very fine powder, works smoothly, is of a dense black color and durable, but dries very slowly in oil.
Vegetable black is a better kind of lamp black made from oil. It is very light, free from grit and of a good color. It should be used with boiled oil, driers and a little varnish. Raw linseed oil or spirits of turpentine keeps it from drying.
Ivory-black is obtained by calcining waste ivory in close vessels and then grinding. It is intensely black when properly burned. Bone-black is inferior to ivory-black, and prepared in a similar manner from bones. In Europe some other blacks are used, but are seldom met with in this country.
When camphor gum is burned and the soot collected by means of a paper funnel or a saucer inverted over it, the result mixed with gum-arabic will be found far superior to the best ivory-black.
Black japan is a composition of asphaltum and oil, and is a liquid of about the same consistency as varnish, of a jet-black color, although of a brownish tint when applied over a light color, or on tin or glass. While ordinary blacks have a greenish hue when varnished, this article will retain its jet color. It has no grains as a mixture of pigment and varnish, and its flowing qualities are good. Many err in supposing that it will cover at once, and thus take the place of color, and furnish with two or three applications a perfect surface over any ground, but this is not the case. It was never intended for such a purpose, it is semi-transparent, and when put upon a white ground produces a brownish tint or glaze.
Besides the black pigments described above, there are several other substances known as Prussian black, black lake and tannin black, which have been proposed as black pigments, but their use is so limited that it is not necessary to give a description of them.
Frankfort black is made of the lees of wine, from which the tartar has been washed, by burning in the manner of ivory black. Similar blacks are prepared from vine twigs and tendrils which contain tartar, also from peach-stones, etc., whence almond black and peach black, and the Indians employ for the same purpose the shell of the cocoanut.
Fig. 14. Handled Roofing Brush.
Inferior Frankfort black is, in fact, merely the levigated charcoal of woods, of which the hardest, such as box and ebony, afford the best. Fine Frankfort black, though almost confined to copper-plate printers, is one of the best black pigments we possess, being of a fine neutral color, next in intensity to lamp black and more powerful than that of ivory. Strong light has the effect of deepening its color, yet the blacks employed in the printing of engravings have proved of very variable durability. It is probable that this black was used by some of the Flemish painters, and that the pureness of the grays is attributable to the property of charred substances to prevent discolorment.
Blue black is a well-burnt and levigated charcoal, of a cool neutral color, and not differing in other respects from the common Frankfort black. Blue black was formerly much employed in painting, and, in common with all carbonaceous blacks, has, when duly mixed with white, a preserving influence upon that color in two respects, which it owes chemically to the bleaching power of carbon, and chromatically to the neutralizing and contrasting power of black with white. A superior blue black may be made by calcining Prussian blue in a close crucible, in the manner of ivory black, and it has the important property of drying well in oil. Innumerable black pigments may be made in this way by charring.
Vegetable black is a pigment now very extensively employed, superseding to a great extent the use of lamp black, to which it is in every way superior. The best way to procure it is to buy it in a dry state, in which it resembles soot, and is so exceedingly light that an ounce or two will fill a gallon measure. It is free from grit, and only requires to be rubbed up with a palette knife on a marble slab, instead of grinding. It should never be diluted with linseed oil, because, if it were, it would never dry, and it is not advisable to employ turpentine, but always the best boiled oil, and a little varnish will improve it. A small quantity of driers should be added, to ensure its drying with a uniformity of surface.
Blues. Prussian blue is made by mixing prussiate of potash with a salt of iron. The prussiate of potash is obtained by calcining and digesting old leather, blood, hoofs or other animal matter with carbonate of potash and iron filings. This color is much used, especially for dark blues, making purples and intensifying black. It dries well with oil. Slight differences in the manufacture cause considerable variation in tint and color, which leads to the material being known by different names, such as Antwerp blue, Berlin blue, Harlem blue and Chinese blue. Indigo is produced by steeping certain plants in water and allowing them to ferment. It is a transparent color, works well in oil or water, but is not durable, especially when mixed with white lead.
Ultramarine was originally made by grinding the valuable mineral lapis lazuli. Genuine ultramarine so made is very expensive, but artificial French or German ultramarines are made of better color, and cheaply, by fusing and washing and reheating a mixture of soda, silica, alum and sulphur. This blue is chiefly used for coloring wall papers.
Cobalt blue is an oxide of cobalt made by roasting cobalt ore. It makes a beautiful color and works well in water or oil.
Smalt, Saxon blue and royal blue are colored by oxides of cobalt.
There are a few other blues, such as celestial or Brunswick blue, damp blue and verditer, that are chemical compounds, compounds of alum, copper, lime and other substances.
Brunswick blue is essentially a mixture of Prussian blue and barytes. It is prepared by thoroughly mixing barytes with water, adding a solution of copperas, then a solution of red or yellow prussiate of potash, stirring constantly so as to ensure the thorough incorporation of the barytes with the blue. After filtering, washing and drying, the blue is ready for use.
As a pigment it is quite permanent and resists exposure to the air, light and most of the other influences which act on pigments. It has the curious property of fading a little on exposure to light and of recovering its original intensity of color in the absence of light.
Prussian blue can be mixed with nearly all other pigments without being affected or changed by them or affecting them in any way.
Indigo, or Indian blue, is a pigment manufactured in the East and "West Indies from several plants, but principally from the Anil, or Indigofera. It is of various qualities, and has been long known and of great use in dyeing.
In painting it is not so bright as Prussian blue, but is extremely powerful and transparent, hence it may be substituted for some of the uses of Prussian blue, as the latter now is for indigo.
It is of great body and works well both in water and oil. Its relative permanence as a dye has obtained it a false character of extreme durability in painting, a quality in which it is very inferior even to Prussian blue.
Fig. 15. Roofing Brush.
Indigo is injured by impure air, and, in glazing, some specimens are firmer than others, but not durable, in tint with white lead they are all fugitive; when used, however, in considerable body in shadow it is more permanent, but in all respects inferior to Prussian blue in painting. Intense blue is indigo refined by solution and precipitation, in which state it is equal in color to Antwerp blue. By this process indigo becomes more durable and much more powerful, transparent and deep. It washes and works admirably in water; in other respects it has the common properties of indigo.
The indigo plant, in its general appearance, is not unlike the lucerne of our fields. The seed is sown in drills, about 18 inches apart, and soon makes its appearance above the ground, when it requires incessant care to keep the weeds down, which would otherwise soon choke so tender a crop. In about two months the plants begin to flower, and are then cut down, but shoot up again and give two or three more crops in the same year. Formerly indigo was carefully dried after being cut, and even fire heat was sometimes used for the purpose; but now, at least in India, the practice is abandoned, and it is found in every respect better to use the plant whilst fresh and green. The first process is to place in a shallow wooden vat as much as will loosely cover the bottom of it; water is then let in so as to cover the plants about three inches, and heavy wooden frames are put on the top to prevent them from floating. Being left in this state for from fifteen to twenty hours, fermentation is set up, and much gas is disengaged, the water becoming a light green color. The green liquor is then run off into the second vat, which is placed below the level of the first, in which, whilst the fermentation process is being repeated upon a fresh supply in the first vat, it is violently agitated by being beaten with poles; this causes the grain, as it is called, to separate, and the green matter suspended in the liquor becomes blue and granular, and this change is promoted by the addition of a little lime-water from time to time. When this operation is sufficiently advanced the contents of the vat are allowed to settle, and in a short time the now intensely blue granular matter has sunk to the bottom, leaving the supernatant liquor almost as clear as water; this is then run off nearly to the bottom, and the sediment is run into the third vat, which is below the level of the second; here it awaits several other additions from successive operations, and, a sufficient quantity being accumulated in the third vat, it is suffered to subside and when thoroughly settled the clear liquor is drawn off, and the granular matter is removed and filled into coarse bags, which are hung up to drain. When sufficiently drained the blue paste is filled into very small boxes, about three inches square, and set to dry in the sun, which soon renders it fit for packing.
There are, of course, other blues, but the above will be sufficient for all purposes, and the painter is urged not to adopt others until he knows their qualities from actual trial, and from having watched the effect which time and exposure to atmospheric action have had upon them.
Browns. Browns generally owe their color to oxide of iron. Raw umber is a clay similar to ochre colored by oxide of iron. The best comes from Turkey; it is very durable both in water and in oil; does not injure other colors when mixed with them.
Burnt Umber is the last mentioned material burnt to give it a darker color. It is useful as a drier, and in mixing with white lead to make a stone color.
Vandyke Brown is an earthy dark brown mineral; it is durable both in oil and water, and is frequently employed in graining.
Purple Brown is of a reddish-brown color. It should be used with boiled oil and a little varnish and driers for outside work.
Burnt Sienna is produced by burning raw sienna. It is the best color for shading gold.
Brown Pink is a vegetable color often of a greenish hue. It works well in water and oil, but dries badly, and will not keep its color when mixed with white lead. Spanish brown and brown ochre are clays colored naturally by various oxides.
Sepia is a brown pigment, of slightly varying hue, and is obtained from various species of cephalopodous animals. It is a blackish-brown pigment of a very fine texture, mixing well with both oil and water. It is much used by artists, especially for monochrome work. It is a fairly 
Fig. 16. Kalsomine Brush.
permanent pigment, being but little affected by exposure to light and air.
Manganese brown is an oxide of manganese, of a fine, deep, semi-opaque brown, of a good body, and dries well in oil. It is artificially prepared from the waste still-liquors of the chlorine manufacturer by precipitating the liquors with sodium carbonate, collecting the precipitate and calcining in a furnace to a low red heat, until samples taken out and allowed to cool show the desired shade. It is a good and permanent pigment, but it is difficult to use on account of its excessively strong drying properties.
Greens. These, of course, may be made by mixing blue and yellow together, but such mixtures are less durable than those produced direct from copper, arsenic, etc. The latter are, however, objectionable for use in distemper or on wall papers, as they are very injurious to health. Brunswick green of the best kind is made by treating copper with salammoniac. Chalk, lead and alum are sometimes added. It has rather a bluish tinge, dries well in oil, is durable, and not poisonous. Common Brunswick green is made by mixing chromate of lead and Prussian blue with sulphate of baryta. It is not as durable as real Brunswick green. Mineral green is made from bi-basic carbonate of copper; it weathers well. Verdigris is acetate of copper. It furnishes a bluish-green color, durable in oil or varnish, but not in water; it dries rapidly, but requires great care in using owing to its poisonous qualities. Green verditer is a carbonate of copper and lime; is not veiy durable. Prussian green is made by mixing different substances with Prussian blue. There are a number of other greens made from copper, but they all possess in a greater or less degree the same qualities as the foregoing. Emerald or Paris green is made of verdigris mixed with a solution of arsenious acid. It is of a very brilliant color, but is very poisonous; is difficult to grind, and dries badly in oil. It should be purchased ready ground in oil, as in that case the poisonous particles do not fly about, and the difficulty of grinding is avoided. Scheele's green and Vienna green are also arseniates of copper, and highly poisonous. Chrome green should be made from the oxide of chromium, and is very durable. An inferior chrome green is made by mixing chromate of lead and Prussian blue, as above mentioned, and is called Brunswick green. The chrome should be free from acid or the color will fade; it may be tested by placing it for several days in strong sunlight.
Bremen green is essentially copper hydrate, and forms an extremely loose and pale blue mass, the color of which has, however, a somewhat greenish tinge. When used as a water color it gives a pale blue, but when employed as an oil paint the original blue color turns green in 24 hours, owing to the copper oxide combining with the fatty acids of the oil to a green copper soap.
Reds. Carmine, made from the cochineal insect, is the most brilliant red color known. It is, however, too expensive for ordinary house painting and is not durable. It is sometimes used for inside decoration.
Red lead is produced by raising massicot, which is the commercial name for oxide of lead, to a high temperature, short of fusion, during which it absorbs oxygen from the air and is converted into red lead or minium, also an oxide of lead. The color is lasting, and is unaffected by light when it is pure and used alone, but any preparation containing lead or acids mixed with it deprives it of color, and impure air makes it black. It may be used for a drier, as it possesses many of the properties of litharge; it is also often employed in painting wrought iron work, to which it adheres with a tenacity not equaled by any other paints; it is sometimes objected to for this purpose, on the ground that galvanic action is set up between the lead and iron.
Vermilion is a sulphide of mercury in a natural state as cinnabar. The best comes from China. Artificial vermilion is also made, both in China and in this country, from a mixture of sulphur and mercury. Genuine vermilion is very durable, but when mixed with red lead, as it is sometimes, it will not stand the weather. It can be tested by heating in a test tube; if genuine it will entirely volatilize, German vermilion is the tersulphide of antimony, and is of an orange-red color.
Indian red is a ground hematite ore brought from Bengal; it is sometimes made artificially by calcining sulphate of iron. The tints vary, but a rosy hue is considered the best. It may be used with turpentine and a little varnish to produce a dull surface, drying rapidly, or with bulled oil and a little drier to produce a glossy surface.
Fig. 17. Flat Knotted Badger Blender.
Tuscan red is essentially a mixture of Indian red with some sort of lake color. The cheapest article is made from a reduced Indian red and rose pink. The richness of such article is very fleeting, particularly if the rose pink be simply whiting colored with a coal tar dye. It is apparent that the real value of a Tuscan red lies in the permanency of the lake coloring material employed to give it richness. Orange is a chromate of lead, brighter than vermilion, but less durable.
Orange ochre is a bright yellow ochre burnt to give it warmth of tint; it dries and works well in water or oil, and is very durable. It is known also as Spanish ochre. Orange red is produced by a further oxidation than is required for red lead. It is a brighter and better color.
Chinese red and Persian red are chromates of lead, produced by boiling white lead with a solution of bichromate of potash. The tint of Persian red is obtained by the employment of sulphuric acid.
Venetian red is obtained by heating sulphate of iron produced as a waste product at tin and copper works. It is often adulterated by mixing sulphate of lime with it during the manufacture. When pure, it is called bright red. Special tints of purple and brown are frequently required, which greatly enhance the value of the material. These tints should be obtained in the process of manufacture, and not produced by mixing together a variety of different shades of color. When the tint desired is attempted to be obtained by this latter course it is never so good, and the materials produced are known to the trade as faced colors, and are of inferior value.
Venetian red originally consisted of a native ferric oxide or red hematite. But of recent years the name appears to have been transferred to a particular quality of artificial ferric oxide made by calcining green vitriol. When this salt is heated in a crucible the upper portion of the product, which has been less strongly heated than the lower, is of a brighter red than the remainder, and after washing and grinding is sold as Venetian red.
Rose pink is made of a sort of chalk or whiting stained with a tincture of Brazil wood. It fades very quickly, but is used for paper-hangings, common distemper and for staining cheap furniture.
Lakes are made by precipitating colored vegetable tinctures by means of alum and carbonate of potash. The alumina combines with the organic coloring matter and separates it from the solution. The tincture used varies in the different descriptions of lake. The best, made from cochineal or madder, is used for internal work. Drop lake is made by dropping a mixture of Brazil wood through a funnel onto a slab. The drops are dried and mixed into a paste with gum water. It is sometimes called Brazil wood lake. Scarlet lake is made from cochineal, so also are Florentine lake, Hamburg lake, Chinese lake, Roman lake, Venetian lake and Carminated lake.
Whites. The most important group of painters' colors are the white pigments. White is the basis of nearly all opaque painting designed for the laying and covering of grounds, whether they be of woodwork, metal, stone, plaster or other substances. It should be as pure and neutral in color as possible, for the better mixing and compounding with other colors without changing their hues, while it renders them of lighter shades, and of the tints required; it also gives solid body to all colors. It is the most advancing color; that is, it comes forward and catches the eye before all other colors, and it assists in giving this quality to other colors, with which it may be mixed, by rendering their tints lighter and more vivid.
White is the nearest among colors in relation to yellow, and is in itself a pleasing and cheerful color, which takes every tint, hue and shade, and harmonizes with all other colors, and is the contrast of black, added to which it gives solidity in mixture, and a small quantity of black added to white preserves it from its tendency to turn yellow.
The most important of the white pigments is
White lead, which may be obtained either pure or mixed with various substances, such as sulphate of baryta, sulphate of lead, whiting, chalk, zinc white, etc. These substances do not combine with oil as well as does white lead, nor do they so well protect any surface to which they are applied. Sulphate of baryta, the most common adulterant, is a dense, heavy, white substance, very like white lead in appearance. It absorbs very little oil, and may frequently be detected by the gritty feeling it produces when the paint is rubbed between the finger and thumb.
Oxide of zinc, or zinc white, is durable in water or oil; it dissolves in hydrochloric acid; it does not blacken in the presence of sulphuretted hydrogen, and it is not injurious to the men who make it, or to the painters who use it; but on the other hand, it does not combine with oil well, and is wanting in body and covering power, and is difficult to work. It is easily acted upon by the carbonic acid in rain water, which dissolves the oxide, and it therefore is unfit for outside work. The acids contained in unseasoned wood also have a great effect upon it. When pure and used for inside work, it retains its color well, and will stand washing
Fig. 18. Camel's-Hair Lacquering Brushes.
for many years without losing any of its freshness. When dry it becomes very hard, and will take a fine polish. This paint is suitable for any place that is subjected to vapors containing sulphur, or in places where foul air is emanated from decaying animal matter.
The purity of white lead is ascertained by dissolving a sample of it in pure dilute nitric acid, 1 part of acid to two parts of water. On adding dilute sulphuric acid to the solution, after diluting it with water and filtering off the precipitate of lead sulphate thus obtained, no further precipitate should be formed on successively adding ammonia, ammonium sulphide and ammonium oxalate to the filtrate.
The purity of zinc white in oil may be tested by burning out the oil by means of a blast lamp, on an iron spoon or ladle. Take of the zinc white a piece about the size of a pea, place it in the center of the spoon and direct the blast on it until it is burned white and perfectly dry. Crush the white cinder which is left to a line powder and drop this into a glass of diluted sulphuric acid, 1 part of acid to 10 parts of water. If the powder be fine and very little dropped in at a time, it will, if pure, dissolve completely before reaching the bottom and without effervescence. If there be any effervescence it indicates the presence of whiting, which will precipitate as sulphate of lime, which is, however, sparingly soluble, barytes is insoluble, and a considerable adulteration of terra alba is not readily soluble; clay is insoluble.
Gypsum mixes well with either water or oil, and, being neutral in its properties, it can be mixed with all other pigments without affecting them or being affected by them. It is used very largely by paper stainers and makers of wall paper, who prefer it to barytes on account of its having more body when used for that class of work. It is used in finishing of cotton goods, in paper making, and for a variety of other purposes where a cheap white pigment is required.
Whiting is sold under a variety of names, such as Spanish white, Paris white, English white. Whiting is the carbonate of calcium, purified by washing. It is prepared by grinding chalk under water to a very fine powder by passing it through several mills. The powder is run into tanks in which the coarser and heavier particles settle, while the liner chalk passes on to other tanks in which it settles. When the settling tanks are full, the chalk or whiting is dug out and dried. When partially dry it is cut into masses of a cubical shape and dried. When dry it is ground.
Paris white is a finer quality of whiting, but the grinding is more thoroughly done. Spanish white is a name given to Paris white sold in a cylindrical form prepared by moulding the wet material into that form, and allowing it to dry in the open air.
Whiting is a dull white powder of an amorphous character, and soft to the feel. It is quite insoluble in pure water, but is soluble in water containing carbonic acid gas.
Kaolin or China clay is essentially a hydrated silicate of alumina. It is a natural product and only requires levigating and drying to prepare it for use as a pigment. It occurs in large deposits along with other constituents of undecomposed granite, the china clay usually forming from 15 to 20 per cent of the whole deposit.
Kaolin is a fine, white amorphous powder, having slight adhesive properties and adhering to the fingers when moist. The best qualities have a very soft unctuous feel and a pure white tint, while the common qualities are rather rougher and of a more or less yellowish hue.
As a pigment kaolin is quite permanent, resisting exposure to the atmosphere and to light for any length of time. It is, however, not much used as a pigment. In oil it loses its body and becomes more or less transparent. It can be used in water colors and in distemper work with good results, and is emjDloyed in paper-making and paper-staining.
Yellows. Chrome yellows are chromates of lead, produced by mixing dilute solutions of acetate or nitrate of lead and bichromate of potash. This makes a medium tint known as middle chrome. The addition of sulphate of lead makes this paler, when it is known as lemon chrome, whereas the addition of caustic lime makes an orange chrome of a darker color. The chromes mix well with oil and with white lead either in oil or water. They stand the sun well, but like other lead salts, become dark in bad air. Chrome yellow is frequently adulterated with gypsum.
Naples yellow is a salt of lead and antimony, supposed to have been originally made from a natural volcanic product at Naples. It is not so brilliant as chrome, but has the same characteristics. King's yellow is made from arsenic, and is therefore a dangerous color to handle, or use for internal work. It is not durable, and it injures several other colors when mixed with them. Chinese yellow, arsenic yellow and yellow orpiment are other names for this yellow. Yellow ochre is a natural clay colored by oxide of iron, and found abundantly in many parts of the world. It is not very brilliant, but is well suited for distemper work, as it is not affected by light or air. It does not lose its
Fig. 19. Round Badger Blender.
color when mixed with lime washes as many other colors do. There are several varieties of ochres, all having the same characteristics differing only in color which varies from a golden to a dark brown.
All the hues and tints, from the palest lemon cadmium to the orange red, are due to one compound only of cadmium, namely the sulphide, which contains 112 parts by weight of cadmium to 32 parts of sulphur. As commonly prepared cadmium yellow is of an orange hue; when this compound separates slowly from a solution, or is made in any way to take a dense or aggregated form, it becomes of a decided reddish orange. The orange-yellow variety, when very finely ground, becomes less red and more inclined to yellow. Some of the palest cadmium yellows contain white pigments or flour of sulphur, added to reduce their depth of color. Yellow cadmium is prepared in several ways. A slightly acid solution of any cadmium salt is prepared and through it is passed a current of sulphuretted hydrogen gas. The product thus obtained has a pure chrome yellow shade. A lemon yellow shade may be obtained by dissolving 1 pound of cadmium sulphate in 4 gallons of water and adding 11⁄4 gallons of the ordinary yellow ammonium, sulphide.
Cobalt yellow is a compound of the nitrates of cobalt and potassium. It is prepared by precipitating cobalt nitrate with sodium carbonate, dissolving the precipitate in acetic acid and adding a strong solution of potassium nitrate. On allowing the mixture to stand for some time the color is gradually precipitated, and is collected, washed and dried, when it is ready for use.
Cobalt yellow is a pure yellow color, and is almost transparent whether used in water or oil painting. Orange ochre also called Spanish ochre is a very bright yellow ochre, burnt, by which operation it acquires warmth, color, transparency and depth.
Mars orange is an artificial ochre similar to the above. It is made by taking equal weights of ferrous sulphate and alum, and adding a solution of carbonate of soda, thereby precipitating the iron and alumina. The precipitate, which forms a yellow pigment, the so-called Mars yellow, is collected, washed well with water, dried and converted into orange, by slightly calcining.
Oxford ochre is a native of the neighborhood of Oxford, England; it is semi-opaque, of a warm yellow color, and of a soft argillaceous texture, absorbent of water and oil, in both of which it may be used with safety, according to the general character of yellow ochres, of which it is one of the best.
Stone ochre has been confounded with the preceding, which it frequently resembles, as does also Roman ochre. True stone ochres are found in balls or globular masses of various sizes in the solid body of stones lying near the surface of rocks among the quarries in Gloucestershire, England, and elsewhere. These balls are of a smooth compact texture, in general free from grit, and of a powdery fracture; they vary exceedingly in color, from yellow to brown murrey and gray, but do not differ in other respects from the preceding, and may be safely used in oil or water in the several modes of painting. Varieties of ochreous colors are produced by burning and compounding with lighter, brighter and darker colors, but often very injuriously and adversely to a certainty of operation, effect and durability.
Raw sienna is a ferruginous, or impregnated with iron, native pigment, and appears to be an iron ore which may be considered as a crude, natural yellow lake, firm in substance, of a glossy fracture, and very absorbent. It is in many respects a valuable pigment, of rather an impure yellow color, but has more body and transparency than the ochres, and being little liable to change by the action of either light, time, or impure air, it may be safely used, according to its powers, either in oil or water, and in all the modes of practice. By burning, it becomes more transparent and drying, and changes color to a red brown. Raw sienna is a valuable color in graining.
There are several pigments called yellow lake, varying in color and appearance according to the coloring substances used, and modes of preparation; they are usually in the form of drops, and their colors are in general of a bright yellow, very transparent, and not liable to change in an impure atmosphere, qualities which would render them very valuable pigments were they not soon discolored and even destroyed by the opposite influences of oxygen and light, both in water and oil, in which latter vehicle, like other lakes in general, they are bad dryers, and do not stand the action of white lead or metallic colors. If used, therefore, it should be as simple as possible.