CADMIUM RED

Regarded as the best substitute for vermilion (which is mercury based as a sulphide of Mercury), it is cadmium selenide and cadmium sulphide. As an oil color it needs a little wax and 40% oil. In tempera the color easily solidifies in the tube and is therefore better for the painter to prepare the color just before use. It is known to turn brown in outdoor frescos; with copper colors such as emerald green it turns black, as do all cadmiums. It should be noted that none of the reds the old masters used were as permanent as the cadmium range. The yellows were introduced to the public at the 1851 Exhibition, and is said to have been made first in 1846. The reds were not introduced until about 1922.

In commercially available colors, it comes in light, medium and dark. These tones vary slightly from manufacturer to manufacturer, and therefore when choosing one for a large area, be sure to have enough from the same source as to replicate the exact tone, and in many cases, the texture of the paint as well. Little is written about the abuses caused by the overgrinding and refining of commercial paint: it can often make the paint gummy in feel, and quite dense, needing extra emulsions to attempt to bring it back to the feel of "paint". There is the opposite extreme as well, which is paint that is saturated with linseed oil. This is usually a sign of a cheaply made color, or one that has not been regarded in the sense of how much oil is needed to produce the proper texture for that tone. Therefore when purchasing paint at sometimes discounted prices, avoid those in tubes yellowing at the mouth and tail by linseed drippings, unless you are planning to use them for glazes. Even for underpainting it will not do, as the paint will be too fat from the excess oil to properly the main coat of color applied after drying. I especially stress this in the cadmium notes as they are more expensive, and sometimes we think we can avoid the price by getting them on sale or from a lesser company. The least expensive way to purchase paint, will always be to buy powdered pigments for grinding, and only make as much as is needed in a sitting; or if grinding for a larger area, some can be capped away for future use assuming it will be used over the next few days. Note: as I may have mentioned, cadmiums should never be mixed with lead white or other lead based paints, but can be mixed with the older Lithopone, Titanox and Zinc oxides, and the more contemporary Titanium whites.

CADMIUM YELLOW

Both permanent and non poisonous, this cadmium sulphide is also permanent in lyes, but behaves oddly when heated: if heated to red it returns to yellow, but turns to orange within a year. Cadmium lemon, is precipitated upon a white filler. Some commercial samples turned green under light, but others stood up well. The darker cadmiums have more covering power and are more permanent. A certain cadmium lemon advertised as 100% cadmium sulphide, revealed titanium white as a base. Today there is a wide range of manufacture and price; but hand made requires 40% oil, a small addition of varnish to act as a slow dryer, and 2% wax to prevent drying in the tube. Cadmium is not compatible with copper colors such as emerald green, as in mixtures with them turns them permanently black. Many cadmiums in powder form show streaks under light; the cause being cadmium salts other than sulphide. It is however useful in all techniques, except fresco, and is permanent indoors. In the open it turns brown when mixed with lime. (See Cadmium Red for history on the yellow range.)

CALCIUM CARBONATE

Also known as Whiting, Marble Dust, Powdered Limestone and precipitated Chalk. It is used in industrial paint manufacture, as an ingredient in grounds on canvas, and as an extender for paints. Marble Dust, which comes in a variety of degrees of grit, is used to add texture to pigments, tooth, and also as an ingredient that brings down the brightness of the color. Most calcium carbonates will do this.

CARMINE OR CRIMSON LAKE

Is a natural organic dyestuff made from the dried bodies of the female cochineal insect, coccus cacti, which lives on various cactus plants in Mexico and in Central and South America. It was brought to Europe shortly after the discovery of those countries, first described by mathioli in 1549. The finest quality, known as nacarat carmine, is non poisonous and quite beautiful with the peculiarity of being more permanent in transmitted light as a transparent color, than when under direct light. According to Maximillian Toch, it is only legitimate as a food coloring, as exposure to the sunlight for three months, bleaches the pigment completely. Carmine lake does not behave much better being even weaker and less stable, is of a maroon shade, and is insoluble in water. It burns completely leaving a white ash, and smells in the process like burnt horn. Despite their rapid fading, these colors continue to be used a great deal in watercolor and oil techniques. Carmine, however, is an aluminum and calcium salt of carminic acid and carmine lake is an aluminum or aluminum-tin lake of cochineal extract, whereas Crimson lake is prepared by striking down an infusion of cochineal with a 5 per cent solution of alum and cream of tartar. Purple lake is prepared like carmine lake with the addition of lime to produce the deep purple tone.

CASSEL BROWN

Vandyke brown, cologne earth: is a brown coal color. Also known as Caste Earth. It is partially soluble in oil and has a slight tendency to turn gray (most apparent when used in whites). When used with resin ethereal varnish it is more permanent than when used in oil, however this is impossible in painting, and unnecessary. It requires 70% oil, and is found in the pictures of the old masters, among them Rubens, who used it mixed with gold ochre as a warm, transparent brown, which held up particularly well in resin varnish. For restoring purposes it is useful when mixed with varnish. Cassel brown is sensitive to lyes and becomes a cold gray in fresco, making it useless on a wall.

CASSEL YELLOW

Mineral yellow, Turner's yellow, patent yellow, is an impermanent lead yellow not compatible with other pigments.

CERULEAN BLUE

This is a greenish, light, very pure and dense compound of cobaltous and tin oxides (is supposed to be a Stannate of Cobalt) which as a color, is very valuable to the landscape artist in atmospheric tones, though this color can also be made by using greenish Prussian blue with zinc oxide. It is absolutely permanent (though in the tube it needs an addition of 2% wax). A cerulean blue bound only in poppy oil becomes solid in a few weeks, "cause being perhaps gypsum". (I don't know what this means, and need to find more information, which so far has not become available).

CHALK

Calcium carbonate; is unaffected by alkalis and remains white when heated. Impure varieties discolor; when they contain iron they turn red. When strongly heated, it is converted into quicklime. Oil colors which contain chalk set quickly in tubes. It is non-poisonous and has little covering power. The whiter it is, the greater the value, therefore French chalks are the best. Gray chalks are however not useful in grounds as they develop ugly dark spots when touched by oil.

CHINESE BLUE

Prussian blue with a greenish tone which is not very permanent.

CHINESE WHITE

Zinc Oxide. Some manufacturers call Flake white, Chinese white, which is wrong, as flake white is generally the other name for lead white, which is obviously of a completely different composition.

CHROMATE OF ZINC

An anti-corrosive used in grounds for paintings that come in contact with steel and iron. Sometimes called Zinc yellow or Aureolin, these are confusing as this puts them in the category of pigments. They are only slightly water-soluble, and are not very useful in painting.

CHROME GREEN

Under this name is sold the valuable chromium oxide green as well as much less valuable mixtures of Paris blue and chrome yellow, which give heavy, earthy tones and should more properly be called chrome yellow-green.

CHROME RED

Similar to Chrome Yellow and also dries quickly. Is basic lead chromate, made by boiling a strong solution of potassium dichromate with white lead and a small amount of caustic soda. It is poisonous and when heated turns a reddish brown. Acetic acid changes it to yellow, whereas vermilion is unaffected. When chrome red is finely ground it becomes a considerably lighter yellowish red, so should be worked only with a spatula rather than a muller, and just before being used. Chrome red is not to be compared with vermilion for brilliancy, and when mixed with white lead, it gives cold, dull tones. It can be used in fresco, but it does not show up well. As a pigment it dates from the beginning of the 19th century; chromium was discovered in 1797, with desriptions of the preparation of properties of lead chromate published in 1809 by Vauquelin, its finder. Little else is known.

CHROME YELLOW

Neutral lead chromate is poisonous, and occurs in manufacture, in all the different nuances from the lightest lemon yellow through light, medium and dark, to orange. The colors are brilliant and relatively inexpensive; they cover and dry well, and as they go a long way, are often cut. The lighter tones do not stand up well under light, and even in powder form turn a dirty leather color, and in oil a dirty greenish brown. The darker shades of chrome yellow are, according to the degree of darkness, much more permanent. Chrome yellow must have 2% wax added to prevent hardening in the tube, to the 25% oil added, which should be poppy oil. When heated it turns a reddish brown, and after cooling again, a dirty yellow. The darker shades can be used in both oil and tempera, and when in contact with wet lime, all tones turn quickly orange. One advantageous color change in chrome yellow occurs in Van Goghs sunflower paintings; his yellows were originally much harder and lighter, and not so mysterious as they appear today. With chrome yellow and Prussian blue are prepared mixed colors, so-called chrome greens, which are relatively more permanent than chrome yellow.

CHROMIUM OXIDE (BRILLIANT & MATTE)

This is one of the best colors and renders all the copper greens unnecessary. Chromium oxide brilliant is transparent, not affected by alkalis or acids, is non-poisonous and dries well. It loses none of its color in alcohol, water or ammonia, and if so is adulterated with coal-tar dye. The color requires 100% oil and must stand for a few hours after grinding, when it will again absorb almost as much pigment as before. 2% wax is added, especially when preserving for tubes. It easily acquires a gelatinous character, especially in tempera, and in manufacture when mixed with fatty oils, there is a separation of a soot-like substance on top of the oil. When it dries on the palette in thick layers in oil or tempera, it looks black, but justly finds many uses, especially with Prussian blue, madder lake of cadmium. If strongly heated, the pigment loses its water content and becomes chromium oxide matte, a dense covering opaque color tone of high tinting strength. It is permanent in all techniques and only requires 30% oil. Even so, it dries no faster than its transparent variety. Because of their ability to withstand the action of acids and alkalis, the chromium oxide greens can be easily distinguished from substitutes.

CLAY

Or Silicate of alumina, which is the base of many of the earth colors, such as umbers, siennas and ochres. Mainly used as an additive ingredient.

COBALT BLUE

A modern replacement for smalt, this is also known as cobalt oxide and aluminum oxide, a non-poisonous metal color, is unaffected by acids, alkalis and heat, and therefore useful in all techniques, as well as being lightproof. It needs 100% oil but dries very quickly, with the same drying power as the metal lead. And because of this it often causes cracks in the picture when painted over layers which are not sufficiently dry. Cobalt blue is susceptible to the yellowing of oils, as all cool tones do, but yields a clear tone whereas ultramarine in thick layers, if not mixed with sufficient white, appears to be black.

COBALT GREEN

Also falsely called zinc green, this is a compound of cobaltous oxide and zinc oxide. It is attacked by hot acids and alkalis and becomes reddish in hot acids, but does not change when heated by itself. The color appears yellowish or bluish when manufactured, and is very permanent in all techniques, but has little coloring strength and is somewhat gritty making it not adhere well. It only requires 30% oil, and the same amount plus 2% wax when in the tube. It dries quickly as all cobalts do, and despite its poor coloring strength, its fine cool tones make it a much used color for flesh tints.

COBALT VIOLET

O the light variety and manufactured by the French, this is a cobaltous oxide arsenate, therefore extremely poisonous and turns dark in oil. Dark cobalt violet, a cobaltous phosphate, is a German product and is very permanent as opposed to the French variety, but is quite expensive, and thus hardly necessary. In tempera it is not a good tube color as it hardens too easily, and in my experience, the commercial watercolors of this pigment also have an extremely short tube life.

COBALT YELLOW

A mineral color with covering power, which Indian yellow does not have, though in manufacture, the color is very uncertain. It is also very expensive, appearing often under the name Indian yellow as well, thus being a superfluous pigment

COCHINEAL

(Also see Kermes). The discovery of Cochineal coincided with the conquest of Mexico in 1523, and was first described by Matthioli in 1549. The insect based red was then brought back to Europe, and I'm curious to know how long after or before, with the conquest of South America, that Brazilwood was also returned to Europe for trade in dyes and pigments.

CRAP LAKE

Also known as Krapp Lak, and is the German name for Madder Lake.

CREMINTZ WHITE

The same as lead white and flake white, but made by a slightly different chemical process which leaves a faint vinegar odor. Not very permanent to sulphur gases, and therefore other whites are far better to use.