Scientists have long known the two chief ingredients of the intense blue pigment: indigo, a plant dye that's used today to color denim; and palygorskite, a type of clay. But how the Maya cooked up the unfading paint remained a mystery. Now Spanish researchers report that they found traces of another pigment in Maya Blue, which they say gives clues about how the color was made.
"We detected a second pigment in the samples, dehydroindigo, which must have formed through oxidation of the indigo when it underwent exposure to the heat that is required to prepare Maya Blue," Antonio Doménech, a researcher from the University of Valencia, said in a statement.
"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," Doménech explained. "It is possible that the Maya knew how to obtain the desired hue by varying the preparation temperature, for example heating the mixture for more or less time or adding more of less wood to the fire."
American researchers in 2008 claimed that copal resin, which was used for incense, may have been the third secret ingredient for Maya Blue. Their research was based on a study of a bowl that had traces of the pigment and was used to burn incense. But Doménech's team didn't buy those findings.
"The bowl contained Maya Blue mixed with copal incense, so the simplified conclusion was that it was only prepared by warming incense," Doménech said in a statement.
The Spanish researchers say they are now investigating the chemical bonds that bind the paint's organic component (indigo) to the inorganic component (clay), which is key to Maya Blue's resilience.
Read more at Discovery News
No comments:
Post a Comment