The chemistry of Maya blue is fascinating since Indigo degrades quickly. To keep the color vibrant, now over centuries, it was encased in palygorskite clay. If

The chemistry of Maya blue is fascinating since Indigo degrades quickly. To keep the color vibrant, now over centuries, it was encased in palygorskite clay. If you are interested in this topic, see also: Veiled Brightness: A History of Ancient Maya Color with Stephen Houston and colleagues, University of Texas Press, 2009 https://utpress.utexas.edu/9780292719002/ https://utpress.utexas.edu/9780292719002/