A separate study in 2014 examined mortar samples from the archaeological site of Río Bec in south-eastern Campeche, finding evidence that Maya stone masons added volcanic ash to the mortar to strengthen it.

Perhaps even more surprising than their stone structures, however, is the preservation of decorated plasters that have also been discovered in some locations. Scientists have known for some time that the ancient Maya knew how to make lime plaster, which they used to coat and protect interior floors or wall surfaces, bind stones together and cover and decorate the surface of stone buildings. Examples of intricately decorated plaster-covered buildings can still be seen in Tikal and Copan, an ancient Maya site in Honduras, today.