New High-Tech Restoration For Mexico’s Oldest Cathedral

In Mérida’s downtown historic center, a delicate and technologically advanced restoration is underway at the Cathedral of San Ildefonso, the oldest of its kind on the mainland of the American continent. 

The Renaissance-Mannerist-style cathedral, erected in the 16th century, is undergoing a meticulous, nearly two-year intervention to heal scars inflicted during a social demonstration on March 8, 2023, when its exterior facades were sprayed with graffiti.

The project, which began in February 2024 and is scheduled for completion in January 2026, represents a fusion of innovative science and traditional conservation strategies. 

Overseen by Mexico’s National Institute of Anthropology and History (INAH) and carried out by the firm IG Restauración y Arquitectura, with funding from a federal insurance program for historical monuments. This initiative addresses not only the recent vandalism but also the underlying deterioration, ensuring an integral approach to the cathedral’s preservation.

At the forefront of the cleaning process is a pioneering technique for such a monument in Mexico: a portable 100-watt pulsed laser. As restorer Karla Martínez López of the INAH Yucatán Center explained, this method was chosen specifically to be less invasive to the cathedral’s vulnerable limestone. 

Traditional chemical or physico-chemical cleaning processes, she noted, are often unfriendly to both the user and the environment, and can be harsh on the historic substrate. The laser, operated by specialized conservators, successfully removed the majority of the surface paint, with only a minimal residue requiring removal through solvents and mechanical cleaning.

The scale of the task is substantial. On the east facade, 40 square meters were treated, while the north facade required intervention across 220 square meters. The current phase focuses on the cathedral’s principal west facade, or portada, where work is reported to be 50 percent complete. However, the project extends far beyond graffiti removal. 

The diagnostic study revealed significant conservation issues in the masonry, including loss of construction joints and plaster, areas of disintegration and detachment, and zones of concentrated moisture. Consequently, the restoration team has stabilized and consolidated original plaster and stone sections and has recovered construction joints using traditional lime-based masonry techniques.

The damage also extended to the cathedral’s wooden and metal elements. Wooden carpentry and associated bronze hardware—hinges, knockers, and fittings—were affected by the graffiti. Furthermore, the three main wooden doors had been painted with low-quality paint during previous interventions, which had caused the wood to dry out and deteriorate. These elements are now being carefully liberated from layers of paint, revealing the original varnish using historical manufacturing techniques. The carved stone frames surrounding the entrances are also being cleaned to harmonize with the restored walls.

A forward-thinking aspect of the conservation involves the application of a special coating designed to protect the stone from weathering and potential future damage from social mobilizations or environmental factors.