Natural dyeing with curcuma
Terra-merita is a vegetable color, produced by the decoction of an Indian root (curcuma longa). The yellow-orange extract is prepared from the root of the curcuma longa plant by drying and powdering, then by solvent extraction, typically with ethyl acetate. The resulting powder is 18 times stronger in the essential ingredients than is the common spice, which is simply a powdered form of the dried root. Curcuma longa extract is a polyphenol that is oil-soluble in its natural state.
This root is also known under the names of Souchet, Indian saffron, Curcuma rotunda, and C. longa (Lin.), according as it is round or elongated. These two kinds come from the East Indies, and differ but slightly. The elongated one is more commonly found in the trade, and is cylindrical, twisted, nearly as thick as the little finger, and orange-yellow inside. Its fracture resembles wax, the thin envelope is like shagreen, its taste is hot and bitter, and the smell is analogous to that of ginger.
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