Cochineal
Carmine, a red dye extracted from cochineal insects, is an example of a chemical product created in nature’s laboratory.
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Used as a vibrant red dye by the Mayan and Aztec civilizations, cochineal became a prized and protected export after the Spanish conquest of the Aztecs during the colonial period. Frenchman Theirry de Menonville became determined to discover the secret source of this dye and in 1777, he voyaged to Cuba and Mexico, posing as a physician and botanist, to advance his scheme. After four years of plotting and adventure, de Menonville obtained specimens of the white insect that when crushed, revealed the coveted cochineal. Ironically, his smuggled Mexican cochineal samples failed to thrive in his cultivation attempts, but one afternoon on a walk around his house on Santo Domingo, he discovered healthy white insects of indigenous cochineal.
Cochineal extract may be made by heating the cochineal insects in an oven, immersing them in hot water, or exposing them to steam or sunlight. Each process results in a different shade of scarlet or orange. The more pure carmine is produced by boiling the dried insects in either ammonia or sodium carbonate followed by the addition of alum to induce precipitation. A purple material can be produced if lime is added along with the alum.
Cochineal’s popularity as a dye increased rapidly when sheep were introduced to Latin America since the red dye binds more tightly to animal-based fibers such as wool or silk than to plant-based fibers such as cotton. Although water-soluble cochineal dye could be adhered to an insoluble support to produce red lake pigment, these colorants were notoriously susceptible to the bleaching effects of light and did not maintain their integrity either in paintings or on the artist’s palette.
More recently, cochineal and carmine experienced a resurgence of use as a natural food coloring when health questions were raised about the safety of a few synthetic red dyes used in food products. In food applications it is one of the most stable reds for light fastness, heat resistance and stability to oxidation and reduction. Carmine is also used in a number of cosmetics such as lipstick, blush, and face powder.
More information about cochineal may be found at http://www.npr.org/templates/story/story.php?storyId=1302796