Maya blue

Maya blue (azul maya) is a unique bright azure blue pigment manufactured by cultures of pre-Columbian Mesoamerica, such as the Mayans and Aztecs. The Maya blue pigment is a composite of organic and inorganic constituents, primarily indigo dyes derived from the leaves of anil (Indigofera suffruticosa) plants combined with palygorskite, a natural clay and type of fuller's earth which is most common in the Southern United States, but is not known to exist in abundant deposits in Mesoamerica. Smaller trace amounts of other mineral additives have also been identified. Maya blue first appeared around 800, and it was still used in the 16th century in several Convents of Colonial Mexico, notably in the paintings of the indigenous Nahua painter Juan Gerson in Tecamachalco. These paintings are a clear example of the combination of indigenous and European techniques sometimes known as Arte Indocristiano. After that, the techniques for its production were lost in Mexico, but in Cuba there are examples from as late as 1830. Despite time and the harsh weathering conditions, paintings coloured by Maya blue have not faded over time. The color has resisted chemical solvents and acids such as nitric acid. Its resistance against chemical aggression (acids, alkalis, solvents, etc.) and biodegradation was tested, and it was shown that Maya blue is an extremely resistant pigment, but it can be destroyed using very intense acid treatment under reflux. Because of its exceptionally durable colour properties, Maya Blue is an iconic system that led to paleo-inspired chemistry, i.e. the recreation of new pigments such as Maya Violet which exploits the molecular structure of Maya Blue towards new pigment combinations. The chemical composition of the compound was determined by powder diffraction in the 1950s and was found to be a composite of palygorskite and indigo, most likely derived from the leaves of the añil. An actual recipe to reproduce Maya blue pigment was published in 1993 by a Mexican historian and chemist, Constantino Reyes-Valerio.