WELD LAKES AND ARZICA

Yellow lakes made from weld were possibly a slightly earlier development than those from rhamnus; but they seem first to have become significant in the fourteenth century. Weld is a tall growing relative of the garden mignonette. It used to be called "dyer's herb" or "fuller's herb." It has a very long history as a yellow dye, for welds (as the crop is called in the trade) is still grown commercially in Normandy and used in dyeing silk. No synthetic dye has been able to replace it in this function. The whole plant, flowers, stems and all, is dried and sold in bundles, and for dyeing and color-making it is broken up and stewed in water or a weak solution of alum. Medieval color-makers considered weld lakes with high esteem when opaque, and preferred buckthorn for transparency. Weld lakes were often precipitated out of the decoction of the plant in alum solution by the addition of chalk, which gave a mixture of an alumina lake with calcium sulphate, only partially transparent. Sometimes weld lakes were precipitated on a base of egg-shells, sometimes on white lead. When white lead was used, the color was a pure, light yellow, as brilliant as orpiment. The weld lakes were sometimes in Italian called arzica, probably a corruption of the old word for orpiment, arsenicon; and it seems quite certain that these colors were specifically thought of as substitutes for orpiment free from its chemical and physiological disabilities.

WHELK REDS

The whelk shellfish are more familiarly known as murex; "murex purple" thus loosely meaning purples of antiquity. Though a good many mollusks yield the porphyry dye.

WOAD & WOAD INDIGO

A substitute for the imported Indian indigo (even in classic times) was known in the native European weed called in Latin, Glastum or Isatic, and in English, Woad: a shrubby herb with broad, green leaves which contain the raw material of a blue dyestuff. Simply gathering the leaves produces a deep and lasting blue-black stain on the hands. Chemically there is little difference between this blue, and that of indigo. As to a difference in their appearance in medieval art, this we can not judge. Both indigos were a very dark, purplish, even blackish color, and less attractive than when it is mixed with a material to lighten it. Even the ancients used to stain white substances with indigo, and in the Middle Ages certain compounds of indigo with whites assumed the character of independent pigments. Color was also sometimes made with a lime made from eggshells.

Many medieval recipes claim to produce a blue "better than that which is extracted from the mineral" A whole family of indigo or woad pigments consisting of mixtures of indigo with powdered marble, natural and calcined, calcined gypsum, calcined eggshells and white lead we now regard as pigments in themselves, independent of the indigo from which they were made. However, considering the extra cost of indigo, naturally it was largely replaced in the middle ages by domestic indigo from woad. Woad was grown commercially in England until the early 1950s as an adjunct to dyeing with true indigo. Its known as a "gross feeder" that exhausts the land its grown on unless the salts it extracts are constantly replaced. This property was capitalized on as no source of potash was more esteemed in medieval England than the ashes of woad. (Potash, from pot ash, meaning the ashes which were made of potassium carbonate). The solutions of this potash were made immediately into dyes, soaps, and other products. But the earth left behind was agriculturally desolate, and the large profits they yielded for a time left the landowners in ruin. Thus they kept moving and using new land, leaving constant wasteland behind them.

Even with the efforts of governments to control these agricultural activities, they never fully solved the problems. Therefore the Middle Ages paid heavily for the privilege of wearing blue cloth. Woad leaves were stripped from the plants, crushed, made up into balls forming the common raw material of commerce in domestic indigo; for use in dyeing they were powdered, spread out, damped and allowed to ferment. They were then made up into a dye bath with water and bran (other materials were used as well) and subjected to further fermentation, all of which took great skill. In the course of dyeing a scum collects on he surface of the vat. Called "Florey" or the flower of the woad, This was skimmed off, dried and used alone or in elaborate compounds under the name of indigo in the Middle Ages. The stench of ammonia and other smells produced by the fermentation isolated the factories from residential and business quarters (in an age where they were not as sensitive to foul odors); the waste from the dyeworks contaminated water supplies, and yet this process went on. Woad indigo wreaked havoc in order to be produced.