The vivid blue paint used in many Mayan paintings and wall decorations is made up of two main ingredients: the indigo plant and a type of clay, researchers say. Scientists were interested in understanding how Mayans were able to cook up a paint type that has not faded, even after hundreds of years. Their research detected dehydroindigo, a yellowish color, that formed after exposing the paint to heat, leading to its greenish-blue color. "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 or less wood to the fire," said researcher Antonio Doménech.
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