Pigments from Plants
Indigo
The term "indigo" derives from the Greek for "from India", where the plant was originally cultivated (Finlay, 2002). Indigofera tinctoria, or "True Indigo" is a shrub growing up to 2 meters in height. The blue dye comes from the leaves of the plant, which is traditionally processed by fermentation. The plants were piled in vats of water and left to decompose. Indigo was immensely popular as a dye for textiles, but was also popular with painters and calligraphers as both an ink and as a dye for parchment (Varichon, 2006).
The Mayans and Indigo
The Mayan culture in the Yucatan peninsula is famous for their use of indigo in their bright, turquoise colored fresco paintings. The Mayans produced the bright hue by mixing a local species of indigo with a special type of clay known as Palygorskite. The clay served to "trap" the indigo molecules in a lattice of clay. The exact technique was unknown to Europeans until the year 2000. "Mayan Blue" was so bright, it was assumed to be a type of metal up until the 1960s (Finlay, 2002).
Madder
Native to Persia, Madder, or, Rubia tinctorum is the only plant to produce a true red, although it may also produce orange and pink colors. The plant's coloring properties are so powerful that it is known to tint pink the bones and milk of animals that feed on it (Varichon, 2006).
Madder is actually a small bush with long, finger-like pink roots, from which the color is produced. Traditionally, the roots were dried in the sun and then pounded with a mortar and pestle to produce an orangey powder. (Finlay, 2002). The resulting pigment may then be mordanted and used to dye fibers. This technique is still in use today for rug weaving.
Pink Madder
Madder is probably best known as a brilliant pink color. However, this color can only be achieved through a pressurized filtration process first developed by chemist George Field . Pink Madder is still produced in very much the same way by pigment manufacturer Windsor and Newton . The pigment is known as Rose Madder, and has been made in regular batches since the year 1835 (Finlay, 2002). Because of the process involved in making Genuine Rose Madder, the pigment can fetch steep prices in comparison with synthetic colors. Today, Windsor and Newton sell a 37mL tube of Genuine Rose Madder for nearly $60 USD.
Madder may also produce a brilliant red, as seen in this Impressionist painting by artist Renoir.
Making Rose Madder at the Winsor & Newton factory.