Restoring San Antonio’s Spanish Missions

On Sunday mornings in San Antonioparishioners file into Spanish colonial missions, just as they have for the past three centuries. Integral in the founding and development of San Antonio as we know it today, Mission Concepción, Mission San José, Mission San Juan, and Mission Espada were constructed by Spanish missionaries in the 18th century.

Today, the Archdiocese of San Antonio operates the four active parishes in conjunction with the National Park Service, which manages the sites. A fifth mission, familiar to many as The Alamo, is run by the State of Texas and is the only one of the colonial missions that does not operate as a church.

In 2010, Old Spanish Missions of the Archdiocese of San Antonio raised over $15 million toward preserving the buildings. The funds have made possible current preservation efforts guided by Ford, Powell & Carson. Principal Carolyn Peterson, FAIA, who has worked on the missions since the 1960s, headed the recent restoration charge while also contributing to the proposal to include the buildings on the UNESCO World Heritage List. The completed restoration of Missions San Juan and San José, as well as an interior restoration of Mission Concepción, are helping to gain recognition for the buildings and the architects’ exquisite work.

The interior restoration of Mission Concepción required the removal and replacement of crumbling plaster. Although the structure was originally built during the 1730s and 1740s, the contemporary mission walls incorporate more-recent plaster from repairs done in the 19th and 20th centuries. Ford, Powell & Carson’s plan was to remove any loose plaster and replace it with a lime-based plaster

replicating the historic 19th-century plaster. However, as they began to work, they made an interesting discovery: remnants of Spanish frescoes on the original wall beneath the 19th-century plaster.

Restoration Associates of San Antonio was brought onto the project to perform a paint investigation. They began by removing the 19th century plaster from areas of the walls suspected to cover original frescoes. Where 18th century paint was discovered, Restoration Associates took photographs and analyzed the pigment in order to replicate the colors later. Remnants of the original frescoes were then consolidated by injecting an acrylic aqueous emulsion to reattach original paint flakes and loose plaster to the wall. The edges were then stabilized with lime putty, sand and microspheres.

Due to their delicate condition, much of the original artwork was recovered with plaster replicating the composition and texture of 19th century finishes. “However, in a few areas, the exceptional Spanish colonial frescoes were left exposed for public view,” explains Anna Nau, architectural conservator at Ford, Powell & Carson. These frescoes were cleaned with distilled water and ammonium carbonate.

The discovery of the original frescoes was fundamental to the overall restoration of Mission Concepción. When the interior was repainted at the conclusion of the project, the hues were mixed to match the pigments of the unearthed frescoes, creating a historically accurate backdrop for next Sunday’s mass.

Rebecca Roberts is currently pursuing a master’s degree in architecture at The University of Texas at Austin.

Article published in Texas Architect May/June 2013. This web version includes expanded content.