Pigments and Dyes

[Dept of PMM Artists & things]

History

The original palette was black, white, red and yellow: charcoal, chalk, and iron rich minerals like red and yellow ochre, very finely ground, which are still used today.

A Chinese text from 3,000 BC lists several recipes for dyes to obtain red, black and yellow on silks. "The bark of the Nieh tree dyes yellow and the Lan (indigo) dyes blue; the boiling of hides yields glue". Another text, written about 142 A.D., refers to earlier traditional manuscripts on alchemy.

Ancient Indian texts describe several different yellow dyestuffs, how to obtain reds from the wood and bark of certain trees, and also note the use of indigo to create blues on cotton. One of the most renowned pigments of the ancient world was Egyptian blue, which is made by grinding up a copper-containing compound: calcium copper silicate. This substance is made by melting sand together with copper minerals and chalk. It was probably discovered as an offshoot of the manufacture of blue-glazed stones called faience, which were first made in Mesopotamia around 4500 BC. Faience was used for decorative purposes, and stimulated experiments with materials and kiln designs that probably also lead to the discovery of glass and of copper smelting, which ushered in the Bronze Age. It was also made in Britain very early on.

By 1500 BC, paint making as an art became quite widely established in Crete and Greece with the Egyptians passing their skills to the Romans. Discorides, the Greek physician and Pliny the Elder, the Roman naturalist, both mention the use of indigo from the Orient to obtain blues, and Herodotus describes its use in a 450 BCE text. Dioscorides also mentions other dye plants of the ancient world, including madder, saffron (Crocus sativus) and weld for yellow, and woad for blue. Walnut shells (Juglans nigra), oak bark (Quercus sp.), pomegranate flowers (Punica granatum) and broom (Genista tinctoria) were also used in conjunction with various mordants; but galls formed on trees could mordant themselves, being high in tannic acid.

A Greek artifact, the Stockholm Papyrus, details dyestuffs and techniques as practiced in Egypt in the third and fourth centuries CE and gives recipes on obtaining purple hues by overdyeing with woad (Isatis tinctoria), madder (Rubia tinctorum), kermes (crimson: made from the dried bodies of the female shield louse or scale insect (Kermes ilicis) and the heliotrope plant (Heliotropium arborescens). It was also known that exposing lead to the fumes of vinegar and animal dung turned it white, owing to the formation of lead carbonate. Known as white lead, this was finest white pigment until the nineteenth century.

Oil Painting

Lacquers were already known in China when the Greeks and Romans introduced varnishes to Europe between 600 BC-AD 400. In oil-painting, a pigment is mixed with a drying agent and an oil. Although its history is not definite, it was known of in ancient times for tinting and varnishing and was used primarily for practical items. Medieval artists knew about oil, but they used it only for special purposes such as coating stone surfaces, painting on metal or as a preservative. It wasn't until the 1420s that the artistic potential of oil paint was discovered in Flanders.

Painting on metal can not be considered permanent, particularly if the work is exposed to heavy wear and tear. Iron and steel will both rust underneath the paint if a rust inhibitor is not used. An undercoat of stiff red lead in oil was traditional. The surface of the metal was roughened first and each coat of paint had to be sanded before applying the next. A coat of pure white lead in oil was stippled on to provide a ground for painting. a mixture of shellac, whiting, silica and graphite can also be used. Patination is also used to colour metals, but it can be a slow process. Steel can be coloured by heating, in various shades from pale yellow to dark blue, depending on the temperature.

Colours

Black:

Most often obtained from a source of pure carbon, often by burning organic material such as bone, oil, or wood, {ivory black) or collecting the soot that was produced in combustion, (lamp black). This soot was then ground. For use as a paint, a water-soluble binder was added to the soot. Black has the advantage of being universally available, inexpensive, and highly permanent.

White:

Chalk, gypsum, lead white. Often mixed with other pigments to obtain pastel shades, particularly blues and purples, or to make transparent colours opaque.

Red:

By roasting white lead carefully in air, you can convert it to lead tetroxide, which is red. This pigment, called red lead, was used in the classical world since the second century AD. The Italian craftsman Cennino Cennini, who wrote a craftsman's manual around 1390, says of it, "A colour known as red lead is red, and it is manufactured by alchemy." In medieval Latin it was called minium, and its extensive use in medieval illuminated manuscripts gives us the word "miniature".

Mineral cinnabar (native vermillion) is the principal ore of the metal mercury. The word 'cinnabar' comes from the Persian for 'dragon's blood'. The crushed ground ore served directly as a pigment for centuries. Cinnabar is fairly widely distributed in nature and sources are known in England, Spain, Italy, China, Japan, California, Mexico and Peru.

The Chinese developed the synthetic version first by cooking mercury and sulphur, in an attempt to discover the elixir of life. A lot of Chinese alchemists died in the process, which is hardly surprising given the following fairly typical ingredients, followed by some useful advice on how and where to make it and how much of it you need for a transcendent dose.

• cinnabar 10 lbs.
• realgar 5 lbs.
• milky quartz 1 lb.
• azurite 5 oz.
• amethyst 5 oz.
• graphite 5 oz.
• saltpeter 1 lb.
• sulphur 5 oz.
• mica 5 oz.
• iron pyrite 5 oz.
• lead carbonate 1 lb.
• Turkestan salt 5 oz.
• orpiment 5 lbs.

"For making this elixir you must locate a spot in the mountain forests that looks down on an east-flowing stream. It should be a spot where humans never pass and where chickens and dogs cannot be heard. Be careful about this! Grind them in order, beginning with the cinnabar granules, five thousand times each...Once the florate elixir is finished, one ounce constitutes a 'transcendent dose.' If one wishes to remain in the mundane world, half an ounce is sufficient."

As if the ingredients listed, which include copious amounts of mercury (in cinnabar), arsenic (realgar and orpiment), lead, and aluminum (mica), aren't dangerous enough already, the alchemist is instructed to put the powdered minerals in a container, pour three pounds of liquid mercury on them and cook them in a furnace.

European use of cinnabar from the Spanish mines began in the early Greek period. Theophrastus, in his History of Stones written in the fourth century BC, says it was obtained from inaccessible cliffs by shooting arrows to dislodge it. By the middle of the eighth century AD Europeans also began making vermilion.

In his manual Cennini described the many pigments available then and how they might be obtained, made and used. He mentions alchemy frequently but not as an esoteric or mystical art. Instead, he regards it simply as a convenient manufacturing method for his colours. Cinnabar, or Vermillion, the finest red pigment of the Middle Ages was, to the alchemists, perhaps the most fascinating substance of all.

The eleventh-century Benedictine monk Theophilus described the synthesis of vermillion in his own craftsman's manual:

"...take sulphur (of which there are three kinds: white, black, and yellow), break it up on a dry stone, and add to it two equal parts of mercury, weighed out on the scales. When you have mixed them carefully, put them into a glass jar. Cover it all over with clay, block up the mouth so that no fumes can escape, and put it near the fire to dry. Then bury it in blazing coals and as soon as it begins to get hot, you will hear a crashing inside, as the mercury unites with the blazing sulphur. When the noise stops, immediately remove the jar, open it, and take out the pigment."

Cennino simply advises the painter to get it ready-made from the alchemists but not ready-ground, because some of them had a tendency to adulterate it with brick dust.

For the Aztec Indians red dye was considered more valuable than gold. Cochineal red, discovered by the Aztecs, was made using the female cochineal beetle. A pound of water-soluble extract required about a million insects and it was the Spaniards who introduced the crimson colour to Europe in the 1500's, although many European artists and craftsmen preferred the original crimson, kermes and did not use cochineal.

Orange:

The only pure orange pigment known until the nineteenth century is realgar, a different form of arsenic sulphide. It also occurs naturally, and was imported to Europe through Venice from Romania and the East. Because it was so poisonous, it wasn't very popular. Cennino warns painters who use it to "look out for yourself".

Yellow:

Further roasting of red lead creates a yellow material: lead monoxide, or litharge. This was used in the Middle Ages as a pigment, under the name massicot. Renaissance yellows were typically compounds of lead, tin and antimony, which the Egyptians had known how to make.

Another brighter, richer golden yellow called orpiment, (arsenic sulphide: the name means pigment of gold) can be found naturally in mineral form, but a better-quality pigment could be had by making orpiment synthetically. Its manufacture was probably an alchemical discovery, as Cennino suggests. It is extremely poisonous, and some painters avoided it for this reason. Cennino warned: "Beware of soiling your mouth with it, lest you suffer personal injury". Yellow dyes can be obtained from a variety of plants and other sources.

Green:

A moderately permanent pigment of varying colour, Malachite is perhaps the oldest known green pigment. It is chemically similar to the blue pigment azurite and sensitive to acids and to heat. In Europe it seems to have been of importance mainly in the 15th and 16th centuries. The name "Malachite" comes from Greek, malache = "mallow" in reference to the colour of the leaf.

Verdigris, a copper sulphate, was made by mixing copper filings with vinegar. The resulting pigment is a brilliant copper-patina colour. However, for all its visual appeal, verdigris is highly caustic to paper and generally unstable. Vergaut (indigo admixed with orpiment) was a popular alternative.

Terre Vert: A natural green pigment varying in compostion and in shades of colour depending on where it comes from, has low hiding power but is unaffected by light or chemicals. Can be mixed with a little white lead to make a beautiful soft green. Green dyes can be obtained from a number of lichens and plants, including the blackthorn berry.

Blue:

"There had never been a blue like ultramarine, and I don't think there ever has been since," says Cennino . "Ultramarine blue is a colour illustrious, beautiful, and most perfect, beyond all other colours; one could not say anything about it, or do anything with it, that its quality would not still surpass".

As its name implied, it came from over the seas, because the mineral from which it is made was not known in the West. Ultramarine is prepared from lapis lazuli a blue stone found in Afghanistan. For centuries, Europeans depended on the Afghan mines for their most precious pigment, worth more than its weight in gold. Ultramarine was precious not just because it was a rare import, but because it was extremely laborious to make. Most mineral pigments were made simply by grinding them up: this was how a green was made from the copper ore malachite, for instance. Ground lapis lazuli, however, turns a disappointing grey because of the impurities it contains. These impurities have to be separated, which is done by mixing the powdered mineral with wax and washing the wax in water, which releases the blue pigment. This has to be done again and again to purify the pigment fully.

Known since antiquity as Lapis armenius, Azurite, a natural basic copper carbonate, is a greener shade of blue than lapis lazuli. The mineral occurs in various parts of the world in secondary copper ore deposits where it is frequently associated with malachite. Its use in Britain is not known before the tenth century AD. Blue dyes include indigo, woad, etc.

Purple:

Vermilion and indigo mixtures produced a particularly successful purple tone.

The heliotrope plant (Heliotropium arborescens) from which a purple dye was extracted, was used as an illuminators' pigment and a food colouring during the Middle Ages. "This Plant which we call Turnsole, the Greeks call Heliotropion, the Sun Follower, because its Flower always turn to the Sun. It bears Beries always three set together, not much unlike the Palma christi; whence it is call'd by Pliny, Heliotropium Tricoccum, the Turnsole with three Berries which when they are at their full Maturity, have within them, between the outward Skin and the Kernel or Seed, a certain Juice, or Moisture, which being rubbed upon Paper or Cloth, at first appears of a fresh and lively green colour, but presently changes into a kind of bluith Purple upon the Paper or Cloth; and the same Cloth afterwards wet in Water or white Wine and wrung forth, will strike the said Water or wine into a red or Claret-wine Colour." - from The History of Druggs by Monsieur Pomet, published in 1709.

Turnsole pigment (also called 'Folium' perhaps because the long tailed 's' in Latin Torna-ad-soleum was confused with 'f'' by later writers) is more correctly a range of colours from blue through purple to red depending on the PH of the solution. The juice was extracted from the berries, soaked into cloth rags and extracted later for use. This process allowed the seasonal dyestuff to be preserved and stored or exported to countries where the plant did not grow. Turnsole rags were being shipped as far as Northern England as early as the 7th century and were used by the illuminators of the Lindisfarne Gospels and the Book of Kells. Medieval pigment recipes instruct the artist to soak a piece of turnsole (rag) in gum-water or glair (beaten egg white) and wring it out to release the dye. Folium apparently became a generic term for any rags of blue-red dye used in this way, whether they were made with the herb turnsole, or from grape juice, mulberry juice, brazil wood, woad, cochineal, lichen or anything else.

These dyes are also called stains, which may explain the origin of a "stain on the escutcheon" in relation to the use of sanguine or murrey (mulberry?) and tenne/tawny, which were frequently used for liveries. With the accession of the Stuarts, scarlet or gules became the livery of the Royal Family. Others are required to use a different red, sanguine, which is now called claret.

Tyrenian Purple, the legendary purple dye of Imperial Rome, was extracted from Mediterranean shellfish. Even Ireland can produce archaeological evidence of dyeing with the native dog-whelk shells in the seventh century CE. The practice was fairly widespread in Europe. Apparently the Phoenicians scoured the coastlines for these whelk shells, and established a dyeworks and trading station wherever they found a plentiful supply. Because it took 12,000 welks to produce 1.5 g of dye, it was never used as a commercial pigment because it was expensive, not very permanent, and difficult to obtain.

Suppliers

Many of these colours, still made in the traditional way, are available from specialist suppliers for conservators and restorers.