For centuries, the vibrant turquoise pigment known as Maya Blue remained a mystery to archaeological chemists. Unlike other organic dyes of the pre-Columbian era, which faded rapidly under the tropical sun or dissolved in acidic soils, Maya Blue exhibited an extraordinary resistance to chemical solvents, acids, and biodegradation. Researchers eventually discovered that this durability was not due to a secret synthetic chemical, but rather to the unique structural fusion of indigo dye and palygorskite, a fibrous clay. In the traditional preparation process, the Maya heated a mixture of indigo leaves and palygorskite clay at temperatures ranging from 150°C to 200°C. This heating process was crucial: it caused the indigo molecules to lose their weakly bound water molecules and migrate deep into the structural channels of the palygorskite clay. Once inside, the indigo molecules formed strong hydrogen bonds with the clay’s silicate framework, effectively locking the pigment in place. The resulting complex prevented oxygen and other reactive agents from reaching the indigo, which made the pigment virtually indestructible. Consequently, murals painted with Maya Blue in ancient cities like Chichen Itza have survived for over a millennium without losing their brilliance, even when exposed to harsh environmental weathering.
According to the passage, what directly enabled the indigo molecules to migrate deep into the structural channels of the palygorskite clay?
- AThe formation of strong hydrogen bonds between the indigo molecules and the clay's silicate framework
- BThe degradation of other pre-Columbian organic dyes under the tropical sun
- The application of heat, which caused the indigo molecules to lose their weakly bound water moleculesAnswer
- DThe exposure of the mixture to oxygen and other reactive agents during traditional preparation