SAFFRON

This was the indispensable element in compounds made for imitating gold. Saffron though attributed to the dried stigmas of the autumn flowering crocus satiavus, may have also been meant to include other kinds of crocus yielding this yellow, the "Oriental" variety most favored in antiquity. For use in illuminating, the painter put a pinch of dry saffron into a dish, covered it with glair, and allowed it to infuse. The resulting extract or tincture, was a perfectly transparent strong yellow. In this preparation it was also used for writing, and mostly painting and glazing over other colors. It enriched greens throughout the Middle ages, and in the fourteenth and fifteenth centuries was added to vermilion, especially in Germany. Greens for books were compounded with saffron and azures, as well as with verdigris and saffron. The glassy saffron alone was used also for ornamental pen flourishings around colored initials, for gold-like frameworks of illuminated panels in books, and for golden glazes and touches in lines of writing in red and black. It was primarily a manuscript color, and in medieval books it has sometimes faded, though not always. It was not used much in tempera on panels, and not at all on walls because of its fugitive character. From my experiences with it, you need a large amount of it to have the tinting quality it describes, but add a little at a time, as quanitities are subjective and vary with pigments.

SALT GREEN & ROUEN GREEN

Two variations on verdigris, popular in the middle ages, were salt green and Rouen green was used from the twelfth century onward. Salt green was made like verdigris, but the plates of copper were coated with honey and salt. And some copper chloride may have been formed along with the acetates. The use of honey with verdigris was fairly usual probably to keep it slightly moist after its application; for verdigris loses some of its richness if it becomes too dry. An excess of honey is suspect as contributing to the tendency of verdigris to spread in manuscript parchment. Rouen green won quite a reputation in France and England in the fourteenth century. Though it was known before and after. It was made by coating the copper with soap before it was exposed to the actin of the vinegar; the result presumably, a mixture of verdigris with some copper salts of the fatty acids from which the soap was made, and some glycerin. These and many other medieval painting materials have still to be more fully investigated synthetically before their importance can be estimated.

SAP GREEN

The most important substitutes for verdigris were sap green and iris green. Sap green is made from the juice of the ripened berries or buckthorn, or rhamnus. Though there are many varieties of green which could be prepared, it is evident from laboratory experiments that some varieties yield inferior colors. We cannot suppose that medieval colorists possessed botanical knowledge which would have enabled them to pick the right kind of buckthorn; but where it grew well, was where it became known, and the best quality available. Its preparation was the squeezing out of the juice, mixed with a little alum, then allowed to thicken by evaporation. The result was a gummy green color, generally rather olive, transparent and rich. As the juice of these berries was used early on without preparation to temper and enrich verdigris, its probable use as an independent pigment came about as a development of its accessory function. Cennino suggests putting a bit of it into a mixed juice, the verjuice as he calls it, but warns that the effect won't last. The color made with alum is more durable, though not permanent in the modern sense. Some of it has however lasted in many manuscripts. It is different from many pigments in that it was not dried nor mixed with a binding medium, as the thickened juice was already sticky. In early times it was sold in bladders as a dense syrup rather than dried. It is still used though somewhat more as a watercolor, and in oil paints now sold under this name they usually contain coal tar lakes.

SCHEELE'S GREEN

An acid copper arsenite; the first artificial green pigment in which copper and arsenic were the essential constituents. First prepared in 1778 by Swedish chemist, Carl Wilhelm Scheele, it was usually made by dissolving white arsenic in a solution of soda ash or potash, and adding the hot arsenite solution of a solution of copper sulphate. The precipitate needed only washing and drying. It is said that the pigment consisted of small and large irregularly shaped green flakes which were only slightly transparent. Since this green is an inferior pigment it was quickly displaced by Emerald Green, which is a copper aceto-arsenite, introduced in 1814. Scheele's green is blackened by lead and is decomposed by acids. It is a yellowish green when made but jades rapidly and is blackened by sulphur-bearing air and sulphide pigments, and is also extremely poisonous, obviously. It can be found in paintings of the late 18th and early 19th centuries.

SEPIA

A pigment from the ink bag of the cuttlefish, is only reasonably lightproof, and is soluble in ammonia, and only good in watercolor. Colored sepia "beautified" with madder lake, sienna, etc., is permanent.

SILVER WHITE

Pure Zinc Oxide, though the name in the past has been used for lead white.

SINOPIA

The choicest source for red ochre in classical antiquity was known as Pontus Euxinus, from the Pontine city of Sinope, according to Pliny in the first century A.D.. A much lighter version of the same could be found in Asia Minor, and as of the 1950s, no source of supply was known of, even though there is a version sold in Italy, which is supposedly of Italian origin. In antiquity, to guard against the sale of imitations, the cakes of color were sealed and stamped, thus known as "sealed sinope."

In the Middle Ages this name came to refer to all red ochre colors; an English derivative of the word, Sinoper, means earth red. Within the title of Red Ochres, there are many variations used to describe the many variations of color; a light and warn tone is known as Venetian Red, or Mars Red. Darker, more cool toned purple versions are called Indian Red, Mars Violet or Caput Mortuum. Terra Rosa from Pozzuoli near Naples has a salmon pink color which is easily recognizable in some medieval Italian wall paintings, whereas the dark wine red of ground hematite is more common on the wall paintings of Florence. Some versions are clear and strong toned, whereas others are tinged by admixtures made up of other minerals besides iron oxides. The Red Iron Oxides, are artificial pigments made from iron ore or the waste material of chemical industries, though they are closely related to the red earths and have very similar properties. However, with these colors, if ground too finely in oil, they have a tendency to bleed, whereas versions of sinopia will not.. English red, which is a light red, is often cut with gypsum when in the powder form, though I have not discovered why yet. This however makes it too dangerous to use in fresco.

All of these pigments need 40-60% oil, possess good covering power, and dry fairly well. When mixed with whites, they yield cool tones, and can be used for all purposes in all techniques. (Mars Red and Mars Yellow also belong here.) I have discovered that sinopias work well as an underpainting when thinned with a reasonable amount of rectified turpentine, whereas the iron oxides are not as useful as they need more oil than is recommended so close to the canvas, and do indeed bleed into the above colors. To return to the yellow ochres for a moment, when they are heated they turn red, losing their chemically bound water content to become thick and dense. Under moderate heat, yellowish-red colors are produced, however, the stronger the heat, the more rich and saturated the color produced, which if mixed with white create colder tones than one would expect. The coloring agent again, is of an iron oxide. One of my sources claimed that the useful light yellow-reds that could be created through these methods, were not at the time sold as tube colors, but warned that the ochres had to be pure and free from adulterant admixtures such as chalk, because this would create quick-lime if heated, and gypsum should also never be present especially if intended for fresco use. None of these colors however, is in any way poisonous. Natural burnt ochres and red ochres often occur in volcanic regions as decomposition products, and also as natural products finely washed on the banks of rivers. The warmer tones are also called burnt light ochre, burnt gold ochre, and flesh ochre, and the cooler tones often have names such as terra rosa, terra di treviso and Naples Red, which is especially strong and beautiful.

SMALT, OR STARCH BLUE

First described by Borghini in 1584. A moderately fine to coarsely ground potassium glass of blue color, due to the small but variable amounts of cobalt added as cobalt oxide during manufacture. The principal source of cobalt used in this preparation in Europe during the Middle Ages appearing to be the mineral smaltite, one of the skutterudite mineral series. IN the seventeenth and eighteenth centuries other associated cobalt minerals were probably used as well (erythrite and cobaltite). The cobalt ore was roasted and the cobalt oxide obtained was melted together with quartz and potash or added to molten glass. When poured into cold water, the blue melt disintegrated into particles, and there were ground in water mills and elutriated. Several grades of smalt were made according to cobalt content and grain size. The quality of color was marked by F(fine):, M(medium), and O(ordinary), and the coarse grades receives the label H(high), and were called in Saxony, Streublau, which means literally blue to be strewn.. There were other grades they were given as well. In the complex ores in Saxony, as they were first roasted, much of the arsenic was volatilized. The oxides of cobalt, nickel and iron were then melted together with siliceous sand, and the resulting product called Zaffre or Zaffera were, in part, sold to potters and glassmakers. The rest of the product was used instead of potash. A violet tint was obtained.

Smalt was a European invention, credited to Christoph Schurer, a Bohemian glassmaker in the mid sixteenth century, though it was available a century before as it has been traced to two paintings from the fifteenth century, and is also suspected to have been used much earlier in the Near East. Also, cobalt ores were used for coloring glass in Egyptian and classical times. The origin or cobalt tinted glass probably coincided with the development of vitreous enamel techniques; near east in origin, as enamels were made from easily fusible powdered and colored materials similar to glass. And it is understandable that a stable blue enamel powder should be used as pigment for painting. AS smalt is a glass, its particles are transparent, and its hiding power is lower, even than that of cobalt blue. Therefore it must be coarsely ground for use as a pigment. When used in oil medium, it has a tendency to settle and streak down perpendicular surfaces. Like all glass based pigments, it is stable unless improperly made, and is better in aqueous media and lime for fresco. In oil, only a dull color is obtained because the refractive index of smalt is so close to that of dried oil. It has been observed to have partially or completely discolored in oil, except when mixed with lead white which helps prevent the loss. Smalt was rarely used for European easel painting after the discovery of Prussian blue in the early eighteenth century, and the discovery of synthetic ultramarine and cobalt aluminate blue (Thenard's blue) in the early nineteenth century. The last manufacture of smalt was reported in England in 1952 by Reckitts Ltd., a firm that no longer exists.

SPANISH WHITE

Calcium carbonate, or another name for whiting.

STRONTIAN YELLOW

Somewhat richer in color than barium yellow, but otherwise has the same properties and reputation to being better than zinc yellow. Partially soluble in water, and when heated becomes yellow ochre, returning to yellow when cooled, but is like zinc yellow in its discoloration to green when in oil. It is used therefore in green mixtures and with darker tones. Mixtures with all three in white are fairly durable.