To make Maya blue, May places ch’oj leaves in alkaline water – using lime or ash – for 24 hours in a concrete vat at his home. Then the mixture is strained and palygorskite clay, collected from nearby caves, is positioned at the bottom of the vat to absorb the tint. After the resulting blue clay is baked in an oven at about 250 degrees Celsius (480F), it is then ground into a fine powder and inserted inside a small flask, ready to sell.