Turnsole

The dyestuff folium or turnsole, prepared from the annual plant Crozophora tinctoria ("dyers' crook carrier", from its use and the curved tip of its spike of florets), was a mainstay of medieval manuscript illuminators from the development of the technique for extracting it in the thirteenth century (Thompson and Hamilton 1933:41). It joined the vegetal-based woad and indigo in the illuminator's repertory, but the queen of blue colorants was always the expensive lapis lazuli or its substitute azurite, ground to the finest powders. According to its method of preparation, turnsole produced a range of translucent colors from blue, through purple to red, according to its reaction to the acidity or alkalinity of its environment, in the chemical reaction, not understood in the Middle Ages, that is most familiar in the Litmus test.

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Folium ("leaf"), was actually derived from the three-lobed fruit, not the leaves. in the early fifteenth century, Cennino Cennini, in his Libro dell' Arte gives a recipe "IXVIII: How you should tint paper turnsole color" and "ILXXVI To paint a purple or turnsole drapery in fresco." Textiles soaked in the dye vat would be left in a close damp cellar in an atmosphere produced by pans of urine. It was not realized that the oxidizing urine was producing ammonia, but the technique reminds us how foul-smelling was the dyer's art.

The colorant was downgraded to a shading glaze and fell out of use in the illuminator's palette by the turn of the seventeenth century, with the easier availability of less fugitive mineral-derived blue pigments.

Turnsole was used as a food colorant, mentioned in Du Fait de Cuisine which suggests steeping it in milk. The French Cook by François Pierre La Varenne (London 653) mentions turnsole grated in water with a little powder of Iris.

Herbals indicated that the plant grows on sunny, well-drained Mediterranean slopes and called it solsequium from its sunflower-habit of turning its flowers to face the sun, or "Greater Verucaria";^[1] early botanical works gave it synonyms of Morella, Heliotropium tricoccum and Croton tinctorium.

Notes

Further reading

• Daniel V. Thompson, Jr and G.H. Hamilton, 1933. De Arte Illuminandi: The Technique of Manuscript Illumination (New Haven: Yale University Press) pp 41-43.