An Investigation of the Painted Finishes of Mission San José de Tumacácori’s Façade: At the Interface of Materials Analysis, Conservation, and Cultural Confluence
Historic Preservation and Conservation
Located near Tucson, Arizona, the Mission San José de Tumacácori is a Spanish-Colonial mission and the primary landmark of significance within the Tumacácori National Historical Park. Begun around 1800 and acquired by the National Park Service as a half-completed ruin in 1916, successive campaigns of repair have stabilized but also obscured much of the original surfaces of its once brilliantly painted church façade. There are comparatively very few mission structures that have not been repainted or replastered. Initial conservation methodologies at Tumacácori were experimental and would eventually give rise to the use of traditional building materials and methods. However in contrast, between the 1940s and 1970s, synthetic resins and non-traditional treatments were heavily employed. Tumacácori’s façade can thus be read as a document in itself - by studying the application of these methods in succession, one can gain a perspective of nearly a century’s worth of preservation thinking and insight into the development of architectural conservation in the United States. This particular investigation of the original polychromatic painted surface finishes of Tumacácori’s façade consisted of archival research, historic contextualization, comparative studies, in-situ investigation, and laboratory analysis – encompassing optical microscopy of the surface finish cross-sections and dispersed pigment layer particles, scanning electron microscopy with energy-dispersive X-ray spectroscopy, Raman microscopy, Fourier Transform Infrared Spectroscopy, microchemical testing, and petrographic analysis of the stucco substrate. Ultimately, the analytical findings of this thesis research will be used as the basis for a pilot conservation treatment to preserve these rare and fragile finishes for the future.