TERRA DI POZZUOLI

A natural cement which was known to the ancients as rich in silicic acid and useful with lime in Pompeii. In fresco it prevents superimposed layers of color from setting, while itself, sets quickly and is quite stable. Other volcanic earths act in the same way, such as Santorin Earth from Greece, (an island in the Aegean Sea.) The burnt ochres and red earths, as mentioned earlier are reliable in all techniques and are resistant to acids and lyes. They require only 40% oil, and for painting purposes, only unadulterated and unimproved colors should be used. They bleed if ground too finely, and like asphaltum, will penetrate into superimposed layers of oil colors. This was not the case however, when they were ground by hand.

TITANIUM DIOXIDE WHITE

A non-poisonous, good covering paint which is useful in all techniques and a 20th century invention. There is certain dispute about its drying abilities, but does remain even in mixtures. It also however yellows easily, especially in tube paints which have been mixed with heavy oil. Avoid any tubes of titanium that have oil residue at the top of the tube when opening, as these will surely yellow, and within a very short time. Titaniums are however, sometimes cut with large quantities of zinc white to improve their drying time and cohesion with the oil.

TOLUIDINE RED

A synthetic, yellowish red, organic dyestuff; one of the most permanent of its kind, and widely used for outdoor purposes where a permanent bright red paint is needed. It can take strong sunlight for some months without fading. It is unaltered by heat up to 150 degrees centigrade, and by alkalis; is insoluble in water but soluble in boiling alcohol. Was first made by the Badilsche Company in Germany, and patented in 1905, but has not generally been offered to the artists trade by this name. It is occasionally found in cheaper colors as a toner or as a substitute. David Davis art supplies sold me a red pigment under this name in 1989. Whether it was the same pigment or a version of it, I do not know, but it is worth investigating if you are interested enough.

TURNSOLE

The name indigo was attached to all sorts of blue vegetable coloring matters in the Middle Ages, except for turnsole which possessed a rival identity of its own. Like indigo, it lent its name to many poorer substitutes. Both were the great medieval organic blues, yet each name was equally applied to colors made from elderberries, mulberries, bilberries and centaureas, and all manner of other vegetable sources. Where indigo and woad indigo were used for all purposes, turnsole was almost entirely reserved for painting, writing and flourishing in books. There are several other names for turnsole, not of which was used long enough to have any consequence, but there are abundant indications that it was also known as folium, and in several fourteenth century texts we find that "Morella is a kind of plant which grows in the land of St. Gijles. Out of this plant three grains are formed in the seed; and cloths are especially stained with these grains so that they yield a splendid color; and this is called folium." Medieval accounts of folium tell us that it is red when acid, violet when neutral, and blue when alkaline, thus Morella as a plant has seeds that contain a coloring agent which exhibits these characteristics. It is a three seeded plant native to southern France ; in Lyte's English botany of 1578, we read that the seed of the small turnsole dies and stain old linen clothes and rags into a purple color. In Holme's armoury of 1688, he states that the leaves have three berries which have a juice or moisture of a purple color from which turnsole is made. All these documents prove that turnsole or folium is the plant now called, Crozophora tinctoria.

Extraction of the color from the seeds was done by saturating bits of cloth with the juice of the seed of capsules, that were gathered in the summer. The juice was extracted by squeezing gently so that the kernels were not broken; when a good supply was collected the cloths were dipped into it, dried, and re-dipped and re-dried over and over until they had soaked up substantial color. For red, plain linen cloth would work, for violet, they were first soaked in lime water and dried so the lime would neutralize the acidity; for blue the cloths were used to soak up the color and then exposed to ammonia to increase the alkaline content.

As a blue it was impermanent and would revert to violet, but this was not considered a flaw, and large quantities of turnsole were used in the later Middle Ages. The turnsole violet was highly esteemed in fourteenth century Italy, as a common and universal shading for all colors. Why turnsole would have been called folium is a bit of a mystery, except that the bits of cloth were kept between the leaves of a book, the "folia", and took their name from those. The clothlets were the most convenient form of colors for illuminators, as it was placed in a dish, wetted with a little glair or gum water, and the color would dissolve out of the clothe and into the medium, forming a transparent stain. Turnsole, as far as we can tell was a medieval invention with a fairly late introduction; as early as the twelfth century perhaps; but was not prominent until the fourteenth. It paved the way for labor saving methods, clothlet colors and technical degradation of manuscript painting. (Clothlet colors needed no grinding or washing). Fourteenth century manuscript painters found that a touch of turnsole in their azurite enriched the blue. In the fifteenth century transparency in the colors was much over-emphasized; thus the popularity of clothlets is related to the stylistic trend. Manuscript painting was turning into a luxury trade with elaboration, richness and succulence of color becoming prime considerations. With the tendency of book painting in the later middle ages to cater to a wealthy, secular clientele, the use of transparent colors to the detriment of form and significance was inevitable; as was the smart handling, the emphasis on costume, genre, gaiety and luxurious fantasy of all sorts.

TUSCAN RED

A red iron oxide brightened with one of the more permanent organic pigments like alizarin red.

TYRIAN PURPLE

From the Murex: first mentioned by Pliny in the first century, as a pigment prepared by Irish monks from Carpillus Purpura. Also from this period were the vegetable purples, which included indigos, along with the red lakes and Dragonsblood.