Volume 15, Number 3, Sept 1993, pp.20-23

Conservation at Mission San Xavier del Bac

by Jason L. Metcalfe

Preservation of a Functioning Church

The conservation of a historic church or mission in the Southwest can be a difficult endeavor to launch. Because of separation of church and state, functioning religious monuments are ineligible for state or federal monies, and fundraising in the private sector becomes necessary. Furthermore, parties involved in organizing and authorizing preservation efforts may have different cultural, religious, secular, or aesthetic training and backgrounds which shape their respective views of the historic monument, and reaching consensus on the goals for preservation or conservation can be difficult.

Mission San Xavier del Bac

Mission San Xavier del Bac, in Tucson, Arizona, offers a case study of the conservation of a historic-religious monument, revealing the unceasing efforts necessary to fund a large-scale restoration job, the extent of deterioration caused by previous stabilization efforts, and a return to an exterior maintenance program using slightly modified traditional materials and techniques.

For the current preservation initiative at San Xavier, many parties are involved in the decision-making process, including the Franciscan priests of the St. Barbara province who conduct religious services and reside at the mission; the Tohono O'odham Indian tribe who make up the primary parishioners and own land around the mission; the Diocese of Tucson who owns the title to the mission; and the Patronato, a volunteer, not-for-profit organization founded to provide consultation for preservation efforts and to generate discussion among the administrating members to establish a preservation program for the mission. All of the administrative branches, excluding the Patronato, have veto power when discussing options concerning the fate of the mission; thus, unity much be reached among the constituents before a project is approved.

The Patronato has been effective in seeing that goals are established and accomplished. It was founded in 1989 when it became obvious that structural problems in the mission's roof existed and needed repair. Its non-sectarian board includes a broad cross-section of the community and a representative from each of the mission's constituents. Since its inception, the Patronato has served as a unifying force in launching the preservation work currently underway at San Xavier. To fund the endeavor, it has received one matching grant and has encouraged corporate firms and local businesses who take interest in the mission's fate to arrange benefits and other charitable activities. Publicity by the Patronato has also helped raise money for the restoration efforts. The director of the Patronato, Bernard Fontana, is quick to discuss the conservation plans or the history of the mission with anybody interested, and the project has received nationwide attention.

It is noteworthy that at San Xavier it has been easier to obtain funds for the preservation of the exterior of the 200-year-old mission than to raise money for the conservation of the interior. This peculiar fact may be due to southern Arizona's identification with San Xavier as a symbol of beauty, survival, and triumph in a harsh desert climate. That secular view of San Xavier is clouded by its origin as a Jesuit--then a Franciscan--mission and Roman Catholic church established within a Native American community to convert its inhabitants to Christianity. Corporate donors may have some reservations about funding the restoration of a functioning church, and associating their donation with the religious history of the mission.

San Xavier Mission History

San Xavier del Bac was established in 1697 by Eusebio Francisco Kino, a Jesuit missionary and explorer. The original structure, which was built to the northwest of the present church, was replaced by the building now standing. Today's San Xavier was begun in 1783, fifteen years after the Franciscans had replaced the Jesuits in Northern Sonora, and completed (with the exception of one bell tower) in 1797.

Two hundred years of southern Arizona desert elements and other destructive forces (the mission has survived two earthquakes and three decades of abandonment during the nineteenth century), as well as previous restoration attempts, have taken a toll on the structure. The fact that the mission is still standing, much less a functioning church, is remarkable in itself.

There is little surviving documentary evidence relating to the architect, builders, and craftsmen. The documentation is clear in indicating the Franciscan priests who oversaw the building of the mission at various stages. The sacristy door was also inscribed in 1797 by Pedro Bojorquez, who may have been a carpintero, and a census taken during the construction of the mission specifically refers to Spaniard.

The design fuses Spanish Islamic (or Mudejar) styles with Mexican "Frontier Baroque," its construction based on a traditional cruciform plan with towers at the front or foot of the church. San Xavier's towers exceed eighty feet in height and the central crossings are topped by a sixty-foot dome. The mission is unique among the Spanish Colonial buildings of the Southwest, as it is roofed with a succession of shallow elliptical brick vaults.1 The church's massive sides were created by building two walls from burnt brick (resembling today's burnt adobe) with random fill between them. The church's exterior walls are an average of three feet thick, and the bases of the towers reach six feet in thickness. The design and construction methods of San Xavier are a logical development of an architectural philosophy which was used consistently in similar forms throughout Latin American and Texas.2

On its interior, the mission has a dazzling array of wall paintings and polychromed and gilded sculptural and architectural elements. The decoration and the wall paintings in the church can be categorized as Mexican folk baroque, however, there are also geometrical elements of distinctly Native American origin. The polychromed figures reflect the mission's association with the Spanish Colonial tradition of sculptural guilds, and although more important elements like the hands and heads of the figures were probably imported from Mexico, their bodies and clothing were made at the site. The decoration in the church is in a style which was at least ten years out of date in important centers in Mexico at the time it was built. The creation of the Academy of San Carlos in Mexico City had officially introduced Neoclassicism in Mexico upon its opening in 1785.

Exterior Preservation Efforts

Throughout this century, there have been efforts to restore the structure and appearance of the mission. Although these well- intentioned projects prevented immediate deterioration and further loss, some created new problems which are being addressed currently.

In 1906, and also in the 1950s, a layer of portland cement stucco was applied to the roof and dome. While this treatment repaired the immediate structural problems and previous cracking, the addition of portland cement to the original clay brick paired two materials with differing rates of thermal activity. Also, moisture infiltrating the cement dissolved sulfates. The sulfates then penetrated the original clay brick and recrystallized, expanding and disintegrating the brick. Salt efflorescence in the clay brick has continued to be problematic for the mission. Luckily, due to the skill of the masons who built the mission and the large size of the bricks used (up to 15 inches on end), the loss of material due to efflorescence has been minimal and a large amount of brick remains intact.

In 1984, a whitewash of portland cement was applied to the exterior walls and a coat of white elastomeric emulsion paint was applied to the entire roof to seal it. The paint was supposed to be impervious to water; it worked for awhile, however, with the intense southern-Arizona heat and sunlight, the acrylic eventually deteriorated. The paint film shrunk, developing small fissures which allowed rainwater to penetrate, trapping the moisture under its surface. In 1988, when Robert Vint (the architect in charge of the exterior conservation) examined the roof vaults, he "peeled up" a small section of the impermeable roof emulsion to reveal thriving mold growth in the dark, damp, and warm environment beneath.

In 1989, to remedy the situation, Vint had the acrylic emulsion and layers of cement removed. Once the original masonry was exposed, he employed a traditional technique learned from his mentor, Mexican architect Jorge Olvera. Two layers of lime and sand plaster (free of soluble salts), bound by mucilage extracted from the nopal or prickly pear cactus, was applied as a "breathing" protective coating. The mucilage was prepared by boiling pads of prickly pear cactus in large kettles and mashing them to obtain the gooey extract used to mix with the mortar. The mortar was also applied to the exterior surfaces of the mission, which were then burnished with smooth river cobbles (also a traditional technique) to compact the surface and reduce the rate of water absorption.3. In addition to the burnishing, a hydrophobic material (aluminum stearate) was added to increase the water repellence. There are problems, however, with the use of a hydrophobe on top of a plaster. Cracks that develop in the plaster as a result of thermal movement become drainage channels when the hydrophobe and gravity convey water across the damaged areas. Consequently, the use of a hydrophobe has been discontinued in the current repairs. Notwithstanding, it is now felt that, overall, the traditional method is best for the long- term benefit and structural integrity of the mission. The lime and sand combination is most compatible with the original brick; however, the finish will need frequent reburnishing and whitewashing: the key to protecting a traditional preservation system for clay bricks is maintenance.

This healthy respect for traditional techniques is an important component in restoring old buildings which is now receiving its due attention. Since the invention of modern conservation materials, their use in building preservation has been overwhelmingly considered "the highest standard." The results, however, project another reality, and in the case of historic buildings, a combination of traditional techniques and slightly modified materials often are the best approach.

Interior Preservation Efforts

The interior condition of the mission has been affected by a number of factors including dirt, climate fluctuations, bat excrement, insect infestation, and moisture penetration from the exterior. In "Study of the Painted Walls and Surfaces of the Mission Church San Xavier del Bac," conducted in 1978-79 by art conservator and art historian Gloria Fraser-Giffords, conservation student Chris Stavroudis, and Arizona State Museum photographer Helga Teiwes, attention was paid specifically to the damage attributable to the leaking ceiling of the dome. Fraser- Giffords used three previous photographic studies (one from 1906, another from 1941, and the last done in 1968) to compare the church's condition to that shown in the historic photographs and to document the damage that had occurred since 1968. Over 2,400 photographs were taken during this 1978-79 survey4, documenting the condition of the interior at that date. The Fraser-Giffords study reveals the existence of water damage, destruction due to insect infestation, and a large amount of dust, dirt, and grime. The Fraser-Giffords team cleaned the dust off a few specific areas of the interior surfaces for comparative photographic purposes, and paint samples were collected for analysis. In her report, Fraser-Giffords also made specific recommendations for future conservation and structural monitoring.

The most recent conservation effort is headed by Paul Schwartzbaum of the Solomon R. Guggenheim Museum in New York. Working with Schwartzbaum are conservators Carlo Giantomassi and Donatella Zari of the firm Giantomassi & Zari in Rome, Italy; Paola Zari, of Rome; Vincenzo Centanni, of Naples; Mario Pulieri, of Rome; and Ridvan Isler, from Turkey. The Schwartzbaum team was contracted by the Patronato after working on the mission San Jose, in Tumacacori, Arizona, in 1988.

The team's conservation plan for San Xavier is divided into five stages for both the wall paintings and the and the sculptures: "consolidation, cleaning, removal of overpaint, application of mortar repairs, and final presentation."5

According to Schwartzbaum's report, "Conservation of the Chapel of La Madre Dolorosa in the Hispanic Church of San Xavier del Bac, Tucson, Arizona," the following methods and materials are being used.

Consolidation. In areas where the intonaco was separating from the brick support, Ledan, a modified hydropic lime, was injected. In areas of paint flaking less sensitive to moisture, a 15% dispersion of Rhoplex (Primal) AC33 in water was applied with a syringe. Those areas of serious paint flaking which were very sensitive to water were consolidated using acrylic dispersion, Rhoplex (Primal) E330:water:alcohol (3:4:13).

Cleaning. The grime in the church consisted mainly of a heavy layer (1/2- 1/4 inch) of airborne debris, candle residue (carbon deposits), insect nests, and infestation. The surface dirt was removed mechanically, wherever possible, with bristle brushes, water, and sponges (sometimes using an intervention layer of Japanese tissue). The insect nests were softened with water or alcohol and then removed mechanically.

Overpaint removal. Most interior surfaces had an organic coating of unknown origin, probably serving as a varnish, which had darkened to a brown- orange color and required removal. The material was removed with denatured alcohol applied through an intervention layer of Japanese paper.

In the 1950s, Henry Milan, a local Tucson artist, had overpainted entire wall paintings in an oil medium; this overpaint was selectively removed using a Japanese paper compress soaked with a solution of alcohol and acetone (1:1).

Mortar repairs. Some deep losses required filling which was executed using a rough mortar of slaked lime:coarse sand (1:3) and finished with a finely sifted mortar of slaked lime:sand:adobe (1:2:1). The fills and areas of loss exposed by the removal of the overpaint were colored using Winsor and Newton watercolor glazes.

The treatment of the sculptures entailed similar techniques. Some figures required consolidation due to lifting paint and detached glass eyes. The cleaning was performed using wool pads soaked in solutions of water, alcohol, and ammonia (less than 5%) used individually or in a combination when required. Desogen was added to the solutions in order to increase surface contact and solvent action; the treated areas were further cleaned with water to remove any traces of the remaining solvents. Areas of overpaint were removed with a solvent mixture of dimethyl formamide:amyl acetate:butylamine (1:1:1). Stucco repairs were administered to losses visible from ground level of the chapel, and minute losses in the hands and faces were filled with a gesso of calcium sulfate. Selective toning and reintegration was performed using Winsor and Newton glazes with Maimeri varnish colors mixed with Paraloid B-72.

To date, Schwartzbaum's team has completed the cleaning and stabilization of the east and west transepts (ceilings, walls, and sculptures) and arrangements are being made to continue the interior conservation, eventually completing the whole church over the next five years.


The current restoration at San Xavier del Bac is another chapter in the extensive history of preserving the mission. This most recent and extensive effort, however, was largely orchestrated by the Patronato. The Patronato San Xavier represents an exemplary model of a non-profit organization whose purpose is to direct, raise funds for, and oversee the preservation and restoration of a historic Southwestern mission. It is imperative for other proprietors of missions and churches in the Southwest to look at models like the Patronato, utilize local support, and establish similar organizations. Fundraising is often the key element in the preservation or restoration of churches or missions in the Southwest, and if specific funds are not appropriated for preservation, needed maintenance can often be neglected.

As architect Robert Vint has expressed, "No building exists in suspended animation. The laws of entropy dictate the eventual leveling of every lump on the landscape, whether placed there by man or nature. Unless continual energy is introduced into a system, ruin will result."1


1. Vint, Robert: "Mission San Xavier del Bac Restoration," in Traditions Southwest, Volume 1, No. 2, Spring 1990.

2. Giffords, Gloria: "Preliminary Study of the Painted Walls and Surfaces of the Mission Church San Xavier del Bac," unpublished report, January 1978.

3. "Earthen Vessel," in Progressive Architecture, May 1992, pp. 128-134.

4. Now housed at the Arizona State Museum, Tucson, Arizona.

5. Schwartzbaum, Paul; Donatella Zari; and Svitlana Hluvko: "Conservation of the Chapel of 'La Madre Dolorosa' in the Hispanic Church of San Xavier del Bac, Tucson, Arizona," unpublished report, August 1992.


An extensive bibliography pertaining to Mission San Xavier del Bac is published in Saints of San Xavier, by Richard E. Ahlborn, Southwestern Mission Research Center, Inc., Tucson, 1974.

About the author:

Jason L. Metcalfe is an undergraduate at the University of Arizona and a pre-program conservation assistant to Gloria Giffords. In the upcoming year, he will be a conservation intern at the Center for Creative Photography in Tucson, Arizona.

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