The architectural carved stonework of the 18th century mission church of San José y San Miguel de Aguayo has long been recognized for its artistic and historic significance. This project addressed the deterioration and conservation of the Sacristy 'Rose' Window. Historical research, stone characterization and condition assessment all indicated that ground salts and moisture are the primary causes of deterioration of the soft local limestone. As flaking and delaminating occur over time, the carving has continued to deteriorate, requiring urgent conservation intervention.