Maya Blue, a vibrant light blue colour, characterizes the civilisation that flourished across Mesoamerica between the 3rd and 10th century. The pigment was used to decorate pottery, murals and statues and has kept its beauty through the ages because of its exceptional stability, a feature that until recently has confounded scientists. Maya Blue resists attack by solvents, acids, bases and temperatures as high as 3000C. This stability has made the chemical analysis of Maya Blue especially difficult as it can not be treated with common reagents. It was only in the 1960s that scientists, using spectroscopic techniques, were able to show that the pigment was composed of two main ingredients: indigo, a vegetable dye, and palygorskite, an unusual magnesium aluminium silicate clay. Unlike many other types of clay, palygorskite has long interior channels. This allows palygorskite to absorb and to hold fairly large amounts of dye. The absorbent properties of palygorskite are also used in anti-diarrhoeal medications such as Kaopectate. Beyond the composition of Maya Blue, however, there is little known as to how the pigment was produced, and what role it played in the Maya culture. But now, a piece of pottery, which has resided since the 1930s at the Field Museum in Chicago, may help solve the mystery. The pottery, along with other objects and human bones was retrieved in 1904 from the bottom the Sacred Cenote in Chichén Itzá. Commonly found in the Yucatan, cenotes are a type of sink hole filled with ground water. A tunnelling microscopy analysis of the Field Museum pottery showed that in addition to the indigo and palygorskite, copal, a natural resin, was also present. It appears that the combination of these three ingredients can explain the resilience of Maya Blue. Copal burns between 100 and 1500C, temperatures that force the indigo dye into the palygorskite channels where it becomes trapped. It is now believed that Maya Blue was prepared as part of a ritual process to appeal to the rain god Chaak. When the sky was persistently blue and the rain failed to arrive, the Mayas would organise a ceremony to prepare the sacred colour. Various offerings would be prepared at this ceremony, and human sacrifices, painted with Maya Blue, were thrown into the cenote. Satisfied, Chaak would then call in the dark clouds to cover the sky and bring in the rain. Or so it was hoped.
Maya Blue, a vibrant light blue colour, characterizes the civilisation that flourished across Mesoamerica between the 3rd and 10th century.