Third Key Ingredient Found in Maya Blue

VALENCIA, SPAIN—Spanish researchers have detected the pigment dehydroindigo in Maya Blue, the extremely durable blue paint used by the Maya to decorate their walls, codices, and pottery. The pigment is formed when indigo oxidizes during heating. “Indigo is blue and dehydroindigo is yellow, therefore the presence of both pigments in variable proportions would justify the more or less greenish tone of Maya Blue,” said Antonio Doménech of the University of Valencia. Varying the temperature and the cooking time may have allowed the Maya to control the color of the paint. Clay is another ingredient in Maya Blue that makes it long lasting.