A Framework for Advancing Historic Preservation Research and Education through Partnership

Alex B. Lim, Exhibit Specialist/Architectural Conservator, Tumacácori National Historical Park

The Mission Church at Tumacácori National Historical Park.

NPS/Alex B. Lim

Abstract

Tumacácori National Historical Park has been collaborating with research institutes and preservation specialists in testing new materials and innovative techniques for preserving earthen architecture. This article summarizes the procedures and outcomes of laboratory and in-situ evaluations on the effectiveness of these new methods between 2014 and 2022. While the generated information is primarily for earthen architecture, the methodology is equally valuable for rendered masonry units. Paid internship opportunities for student conservators were equally valuable.

Introduction

The Spanish colonial mission structures and fragments at Tumacácori National Historical Park (NHP) is one of the first federally recognized Hispanic sites in the nation’s history. At its core is the Mission Church and, together with supporting structures and agricultural fields built around it, they form an impressive cultural landscape that tells the stories of integration, resistance, and coordination in the U.S.-Mexico border region. The mission buildings are made mainly of adobes, bricks, lime render (plaster/stucco), and multicolored paint finishes. The materials assembly and design of the mission remains at the park offer spectacular opportunities for understanding the methods and the use of Spanish Colonial construction. Current efforts to slow down the rate of decay embrace traditional methods as well as current scientific approaches. Therefore, the partnership model practiced at the park is one of the most effective ways to train the next generation of architectural conservators.

The Cooperative Ecosystem Studies Unit (CESU) network offers an excellent framework for meeting both investigative and educational goals for preservation projects. While the park has a competent in-house team to care for earthen architecture’s hands-on needs, CESU network partners provide specific historic preservation research and technical capabilities. This critical partnership enables the park to further expand knowledge of Spanish Colonial architecture and to push the boundary of preservation techniques and implementations. The University of Pennsylvania, the University of Arizona, and the University of New Mexico have all provided excellent faculty guidance and mentorship with an equally impressive array of graduate and post-graduate interns. Along the way, the park has also benefited from the professional inputs of the National Park Service (NPS) Southern Arizona Office and the Vanishing Treasures Program.

Four common threads exist across all the preservation projects: (1) they improved the condition of the Mission Church remains and protected the original façade; (2) the projects are clearly documented through drawings, photographs, and reports so that the information could be verified and the methodologies shared and repeated; (3) the projects engaged the next generation of architectural conservators through paid internships under dedicated mentors; and (4) the information generated from the preservation projects have directly feed into interpretative programming at the park.

This article summarizes select phases of these collaborative projects, all with substantial intern involvement. It also briefly outlines the implications for management actions and future research needs. The projects are grouped in two parts: (1) recording, documentation, and archival research, and (2) treatment and implementation.

Recording, Documentation, and Archival Research

Investigation of the Church Façade Painted Finishes

The façade, as the face of the church, is the most recognizable feature of the park, yet its documentation and treatment had been sporadic at best. As part of this project, full assessment of the integrity and conditions of the façade were designed and implemented just in time for the NPS centennial. The project was particularly successful in honoring the park’s legacy of celebrating local history and culture through preservation.

Comprehensive recording and documentation of the façade using photogrammetry (using ortho-rectified photographs to create images of the buildings with accurate dimensions), AutoCAD (drafting and design software), and ArcGIS (geographic information system for analyzing geo-locatable data) have resulted in maps and drawings visualizing the overall integrity, history of change, and conditions (Figure 1). For example, when the team quantified the current state of the façade using ArcGIS, it showed that 14% of the original plaster still survived on the 2,200-square-foot façade surface. Until then, the authenticity was subjectively defined as good, fair, or bad. The rest was either lost or stuccoed over. Now one can quantify the conditions and the integrity and can more accurately monitor change.

Figure 1. A section of the Mission Church façade surface conditions map (Chan 2015).

Furthermore, through materials analysis, mineral pigments were identified and matched to the existing database from the interior painted finishes (Chan 2015; Figure 2). Pigments and binders were identified using microchemical testing and particle dispersions (identify chemical compounds/minerals using chemical processes) as well as optical (standard high-magnification microscopy), scanning electron microscope (yields sample surface images at 1 cm to 5 micron level, also able to identify chemical elements present), Raman microscopy (method used to identify molecules).

Figure 2. Mineral pigments used on the Mission Church (Chan 2015).

One very interesting finding was that some finishes were not applied as true fresco but rather stained. A method of staining limewash using ferrous sulfate was confirmed, a practice often done on Spanish Colonial missions in the New World (Johnson and Cliver 2002).

The archival research for this project produced an impressive amount of background information on traditional Spanish painted finish practices in the continental North America and the Caribbean. The park volunteers and docents used that information to understand and share how and why the Mission Church was painted in multiple colors.

Implications for management actions

The visual records from the project serve as verifiable and repeatable references for future stewards of the site that allow them to measure rates of loss. This translates into more precise treatment project development in the future. Continued monitoring will be a key.

It is remarkable to confirm the presence of multi-colored finishes on a Spanish building. Here lies the importance of the park in relation to similar sites in Arizona and Sonora, Mexico. The exteriors of most sister missions in Sonora, Mexico are now whitewashed in lime. As a result, polychrome finishes are invisible or presumed lost. Through this project, the team has found that painted finishes are more durable than most people think and the past practice of using multi-color decoration was more common. The common misconception about the mission church exterior being monochromatically white was dispelled. This information, paired with interpretative techniques employed at other sites such as the San Antonio Missions in Texas or Saint Climent in Spain show exciting new possibilities in using laser/light technology to bring to life the full visual experience of multicolored finishes on Mission Church walls without compromising the overall integrity.

This project continues to serve as a model for other historic sites with similar architectural features. The park has been assisting the Patronato of Mission San Xavier del Bac in Tucson with technical information and with general guidance on project development, a testament to the value of the project.

Future needs

While the project stabilized the areas of immediate concern, comprehensive work on the façade is still left to be done. Recent structural investigations have shown that the façade is pivoting outward and is detaching from the nave at the top. As a result, through-wall cracks have developed leading to localized spalling of the lime stuccoes. The ongoing collaboration with engineers will identify the severity of this problem and lead to actionable treatment options to improve the conditions of the Mission Church and the visitor safety.

Staining limewash with ferrous sulfate or vitriol is a viable restoration/preservation method for certain façade elements that is historically correct. This method is yet to be tried on site and deserves further exploration.

Check out these references for more information

Saint Climent de Taüll – First permanent projection mapped church. 2014. 
Videomapping a Saint Climent. 2014. 
Seeing the (San Antonio) missions in a new (old) way. 2016.
 

Condition Assessment of the Church Interior Lime Finishes

Graduate students in the Heritage Conservation program at the University of Arizona carried out detailed conditions assessment of the Mission Church interior (Caroli et al 2016, Caroli 2015). They developed a visual glossary of terms for surface integrity and conditions. They used this to comprehensively map the integrity and conditions of the church nave and sanctuary. Using the photogrammetric images generated by the NPS Southern Arizona Office, they recorded all the conditions and construction features. Their hand-drawn recordings were then imported into AutoCAD for digitization. The digital maps of architectural integrity, conditions and construction details are now available for viewing and editing (Figure 3).

Figure 3. Conditions map of the west interior wall (Caroli et al. 2016).

Implications for management actions

This project is a clear example of the value of architectural recording and documentation of a historic building. The park leveraged the final product to fund the treatment of the interior and the documents became instrumental during the compliance process with Arizona State Historic Preservation Office in Phoenix. Thanks to the recording, all parties were able to agree on the clear need for preservation work on the church interior and the types and locations of the work to be done.

There are numerous other condition maps and drawings of the church interior prior to this project, however, this was the first time a comprehensive mapping of the integrity and the conditions of the walls was done and translated into digital format for future editing and update. Comparative and quantifiable analysis of change over time is now possible. The impact of climate change on the structure can now be visualized and quantified by comparing changes in calculable surface areas or linear features in ArcGIS. The change in material integrity can be confirmed visually. For example, a structural crack is defined in definite length at the moment of the condition survey. This information is then used for project development but is also used as a reference point to demonstrate active or inactive areas of damage. In addition, the efficacy of previous treatments can be documented and measured. By visualizing repairs at a given point in time, in relation to the damages they were meant to address, one can track how the treatment is working.

Finally, graduate interns with no prior experience conducting full condition assessments were taught how to quantify damage and repair and to visualize the material integrity as well as conditions. This is significant because it allows the park to draw quantitative conclusions from the generated data, instead of relying on surveys using a subjective scale of “good, fair, or bad.” This project confirmed that local partner institutions, with readily available resources, including faculty, students, and facilities, are mobilized for meeting the respective organizational missions of the NPS and a university: preservation and enjoyment of heritage sites for the NPS and professional education and instilling the desire for life-long learning for the University of Arizona.

Future needs

The condition glossary from the project is typical of other earthen architecture in the world, however, there is no standard glossary shared by the profession, which causes unnecessary confusion and inefficiency over time and across regions during project development and execution. The ongoing initiative at the Getty Conservation Institute and the International Council on Monuments and Sites to create a universal earthen architecture terminology/glossary is a welcome next step to help professionals in the field to share the same terminology (Vasquez and Marcus 2022). The NPS should partake in this effort, by feeding the information generated from the project to the overall effort for standardization.

Since project completion, new projects were launched at the park based on this important documentation work. For example, the ongoing treatment of the church sanctuary employed additional methods of documentation using ultraviolet and infrared lights to detect past treatments on the painted surface not visible to naked eyes (Yang 2022). The methods will be fine tuned to better understand the impacts of past treatments to the original painted surfaces and to investigate methods for their mitigation and removal.

Assessment of Load-bearing Wooden Features of the Mission Church

While most people associate the park with adobe and lime plaster, a significant amount of wood is used as well. This project addressed this overlooked part of the earthen construction.Under the partnership agreement with the University of New Mexico, conservators from Anthony & Associates and Porter & Associates were hired as subcontractors and asked to investigate the condition of the loadbearing wooden features of the church, including the roof timbers (referred to as vigas in Spanish) and the lintels above windows and doors (Anthony 2009, Bass et al 2016; Figure 4).

Figure 4. Door and window lintels in the east interior wall of the sanctuary, looking northeast.

NPS/Alex B. Lim

The team relied on visual inspection, wood moisture readings, and resistance and hand drilling into the wood cores. Resistance drilling is a destructive technique for determining the relative density of wood as an indirect indication of its structural soundness. The level of destruction was considered minimal given the small size of the needle relative to the vigas and the limited number of sample holes per each wood unit. The machine prints the relative density of the wood in real time as the needle penetrates the wood. The drilling was conducted on or near the sections of the vigas placed in the wall as well as on most lintel timbers. Hand drilling was also used qualitatively to look for signs of decay.

The study revealed that most of the vigas are Douglas fir (Pseudotsuga menziesii) whereas the lintels are mostly yellow pine (Pinus spp.). The roof vigas have all been replaced and subsequently repaired again by the NPS, and no original roof timbers remain. However, the team concluded that approximately 60 percent of the lintel timbers is original.

Implications for management actions

At the moment, there is no serious urgency for treating wooden features of the church vigas. However, select door and window lintels are determined to be structurally compromised, due to the past and ongoing termite damage; they need immediate treatment.

Future needs

Natural weathering of wooden features could be slowed down and remedied by applying linseed oil on the surface (Gibbs and Wonson 2021). Applying it on the surface of the sun-exposed wooden features would extend their service lives by softening the direct solar and thermal impacts.

Continued monitoring of the roof vigas–even though not original–is critical for the roof diaphragm to keep the adobe walls of the church in place, including the displacing south nave wall (façade). Of particular concern is the roof leak on the northwest side, detected since 2021. This needs active monitoring to avoid wholescale roof replacement as a result of deferred maintenance, a costly and potentially destructive intervention.

Development of Master Database on Church Repair History

All decisions for intervention and preventative treatment are premised on the observations and monitoring that take place over time. It is much like a doctor asking for patient’s medical history. Without fully understanding the site’s history, the stewards run the risk of misdiagnosis and improper treatments. The result is poor performance of the treatment, often resulting in irreversibly adverse effects on historic structures. To avoid this, thorough archival research and data management are necessary. Unfortunately, because this process takes time and because remedial treatment action seems more urgent and practical, data management typically takes the back seat.

To compile available data and to make it more easily searchable for practical use, the team from The University of Pennsylvania reviewed all available documents that detail the works done on the church since 1908, when the park was established. Then they compiled the information in several relational databases. The users of the system can type a keyword and the program will generate a full list of documents that include that keyword in an organized table format (Jang et al. 2017a and b).

Since then, both conservators and interpreters have readily accessed the databases to pinpoint what was done and when on the church, without having to perform comprehensive archival research every time a new project is launched. They are then able to relate the findings to interested parties with improved precision and hindsight.

There are four parts to the database:

1. Master Bibliographic Records – A list of all the documents that they referenced and used to generate keywords.
2. Master Chronology Survey – A list of past repairs organized in chronological fashion.
3. Master Historic Photograph Survey – A list of an extensive number of photographs, both in print and digitized, maintained by the park.
4. Master Condition Survey – An updated condition survey, developed by the University of Pennsylvania that built on the initial efforts by the University of Arizona.

Implications for management actions

Data management for a site spanning more than 100 years of stewardship can be quite daunting, however, in an environment where park staff constantly move and institutional knowledge can be ephemeral, it is critical that the park’s stewardship records are integrated, easily accessible, and verifiable. This way, new park staff spend less time in becoming familiarized with the details of the park’s preservation history, but can instead spend more time making critical assessments to improve the park’s operational efficiency.

The improved organization and access to well-managed data also ensures that new staff members do not duplicate efforts as they plan for preservation projects. The database clearly demonstrates that the park has already tried various methods to slow down the rate of decay of the church over a century. By using such a database, the park saves time by avoiding something that was already done and failed. This information is also useful for other parks with similar stewardship issues.

Future needs

Since the creation of the databases, new projects have been carried out and more findings have been made. Updates to the database files will be needed over time. A series of workshops can inform new staff members and volunteers how to use the databases.

Consolidating Fragile Lime Plaster Using Nanolime Particles

Limewater is a clear liquid layer that forms above lime putty precipitates. While clear, it contains superfine lime particles suspended in water, invisible to the eye. Microscopically, nanolime particles are essentially stacks of plates. Each plate is a hexagonal Ca(OH)₂ suspended in water. When applied into fragile lime plaster and limestone, the particles function like a glue and consolidate them. In the past, limewater, as a byproduct of hand-mixed lime putty, tended to contain lime particles of different sizes, leading to unreliable mixed results for consolidation. Alternative consolidation materials were investigated in the last 50 years, the most common one being ethyl silicate, Si(OC₂H₅)₄.

The production of commercial limewater with lime particles at the nanometer scale (nanolime) in recent years has been groundbreaking in the field of preservation. The park was the first place in the U.S. to test its suitability for use on lime plaster consolidation and the first to use it. The difficult part in using nanolime for consolidation has been its uneven delivery into failing lime plaster or limestone. The goal is to completely saturate the fragile lime plaster with nanoparticles, instead of just the surface. For improved delivery, the nanolime is suspended in alcohol; through capillary action, lime plaster then absorbs it into its deepest pores. In reality, nanolime does not always enter all the way in for several reasons.

To test the viability of nanolime in strengthening the fragile lime plaster inside the church, the University of Pennsylvania carried out an extensive literature review and tested several methods using facsimile lime render samples (Jang and Matero 2018, Jang 2016). One test involved measuring the splitting tensile strength of the samples before and after consolidation. This measures its mechanical strength and indicates if it has become less fragile. The consolidated sample showed an approximately 45% increase in its strength after 28 days of curing. This was very encouraging because it occurred without significant changes to its porosity, permeability, color, and frost resistance. The team fully adopted the method for treating the entire church interior.

To improve the efficacy of the method, the team temporarily covered the walls to retard alcohol evaporation. High ambient relative humidity during summer and winter rain seasons also slowed evaporation.

The whitening of the treated area was an initial concern, but upon fine-tuning the recipe and delivery method, the team concluded that the discoloration was negligible. Where the whitening effect was severe, a technique called acqua sporca (“dirty water” in Italian) was used to mediate the discoloration. The result was materially and aesthetically satisfying.

Implications for management actions

The use of nanolime increases the arsenal of treatment options to slow down lime plaster decay. The use of alternate consolidant such as ethyl silicate with significant health and safety risks could be avoided. Lime particles suspended in alcohol are environmentally friendly and safe to users. The use of sustainable and environmentally friendly conservation products is much in line with the NPS mission.

Future needs

Nanolime has not been used on exterior walls at the park, mainly because of high cost and a limited amount of original plaster fragments still left on the exterior. Nonetheless, the consolidation and protection of the exterior original lime stuccos are urgent as they are in fragile condition and most loss of original fabric happens on unconsolidated exterior original lime stucco. In particular, the original stucco left on decorated façade and the exterior of the north walls of the church are in perilous condition despite being character-defining features that tell the building’s construction history. Nanolime can give a crucial life extension for these fragile areas and should be tested on the exterior.

Left handprint (lower arrow) and trowel mark (upper arrow) on the exposed original scratch layer of the east exterior nave wall of the church. Nanolime consolidation technique may allow preservation and display of this important construction history for public access.

NPS/Alex B. Lim

Crack and Void Repair Using Soil-based Injection Grouting

When a piece of lime plaster detaches from its substrate adobe wall, there are several options to reattach it back. Prior to the 1980s, the NPS and other historic site stewards used nails, chicken wire mesh, screws, and even bolts to physically keep the sections in place. However, these methods are intrusive and cause additional damage to the integrity of the original fabric. They are iron-based and prone to rust and oxidation, causing additional damage over time.

As an alternative to this practice, lime-based injection grout has been developed and used at Fort Union National Monument and elsewhere in the 1990s. The method has been fine tuned over the years, but its rigidity is its biggest downside (Biçer-Şimşir and Rainer 2011). Seismically active sites, such as Tumacácori NHP, prohibit lime-based grout as it is too rigid for accommodating shaking and ground movement. The separation is inevitable and irreversible.

At the park, the University of Pennsylvania team tested an alternate injection grouting method using soil. Soil is readily available as an intervention material and its applicability as injectionable grouting for earthen architecture in recent years has been tested in Europe and South America, as well as in the U.S. (Silva et al. 2012). Encouraged, the team developed custom-made soil grout to readhere detached lime stucco onto adobe walls or to fill in hard-to-reach voids behind lime stucco. A University of Pennsylvania graduate student pushed the boundary of the use of soil injection grout based on extensive literature review and laboratory and field testing (Declet 2017). She developed samples to meet the ideal properties of the preservation material. In other words, she developed a recipe that can be verified and improved as needed in the future.

Implications for management actions

Restoring volumetric homogeneity by filling in the voids and cracks in adobe walls is critical for two reasons: seismic resilience and preventative maintenance. Seismic vulnerability of the mission church was identified early on given its history of earthquake damage. Soil grouting the voids behind the detaching lime plaster improves their condition and creates a safer visitor experience. Wildlife, including insects, animals, and birds, take advantage of the voids in the wall as habitat. Preventative grouting can prohibit opportunistic animal and insect activities.

Future needs

The use of soil grout is yet to be tested on site for remedying structural deficiencies, such as the through-wall crack near the church entrance. This is one of the most serious problems and needs immediate attention. If widened, cracks can further compromise areas containing architectural and decorative features not yet completely studied.

An alternative to crack-grouting is to disassemble the wall, adobe by adobe, and restitch the crack. Obviously, this is not only time consuming, but can only happen with great sacrifice to the integrity of the original wall. Furthermore, if original painted finishes still survive on the affected area, as is the case with the church, the damage will be even more severe. Soil injection grouting for structural reinforcement offers an alternative method; it can enter uneven, irregular, and often hard-to-see void spaces without having to disassemble the wall. It deserves further research.

Nicole Declet of San Juan, Puerto Rico (intern through the University of Pennsylvania) treating an interior surface.

NPS/Alex B. Lim

Conclusion

Building on past successes, the park is continuing these and other partnerships to advance preservation research. The tradition of preservation training, education, and mentorship, outlined in the park’s general management plan, is very much alive and ongoing, thanks in part to the initiatives highlighted in this article.

The park is proud to have served its part in giving the partner institutions and their promising conservators fieldwork experience and research opportunities. Technical research and education are the hallmarks of research institutions; the NPS reaps significant benefits by partnering with them through the CESU framework. The NPS pushes the envelope on the technical research side and can address the NPS’ limited historic preservation research capacity. It is true that an institute such as National Center for Preservation Technology and Training exists and promotes national-level research; yet, site-specific needs, highly dependent on local customs, regional climate, and maintenance/repair traditions, sometimes require different approaches. CESU projects are incredibly flexible to tailor the research goals and methodologies based on the park’s needs and capacity.

Perhaps the most enduring legacy of the CESU partnership is the opportunity for students to gain real-time field experience on site. The park’s experience has shown that the paid interns who have carried out research under the guidance of the experienced principal investigators moved on to find careers with the NPS. They have also joined competent private companies, potential contractors who can contribute to the NPS’s mission. When a career in preservation is encouraged through the paid internship or employment under the CESU framework, a steady pool of preservation students will continue to enter the field. This is vital to the sustainability and quality of NPS preservation effort. One of the biggest problems facing NPS is a lack of experienced conservators and craftspeople joining and remaining in the NPS workforce; the CESU framework partly addresses the problem. The park’s experience working with the passionate, skilled, and dedicated future leaders in preservation has clearly shown that NPS internship opportunities are crucial in developing the professional skills and experiences necessary to sustain the NPS’s ability to care for the nation’s cultural heritage.

References

Anthony, R. 2009.
A grading protocol for structural lumber and timber in historic structures, May 2009, NCPTT Grant No. MT-2210-05-NC-05.

Bass, A., R. Anthony, C. Citto and D. Porter. 2016.
Part 2: Study of exterior dome renders, roof drainage, and structural wood at the Mission Church, unpublished report for Tumacácori National Historical Park.

Biçer-Şimşir, B. and L. Rainer. 2011.
Evaluation of lime-based hydraulic injection grouts for the conservation of architectural surfaces: A manual of laboratory and field test methods. The Getty Conservation Institute. Available at: https://www.getty.edu/conservation/publications_resources/pdf_publications/evaluation_grouts.html (accessed August 5, 2022)

Caroli, R., M. Beggy, S. Herr-Cardillo, B. Lehmann and R. B. Jeffery. 2016.
Interior condition assessment report, Tumacácori National Historical Park, The Drachman Institute, College of Architecture, Planning, and Landscape Architecture, The University of Arizona.

Caroli, R. 2015.
An interior conditions assessment of Mission San José de Tumacácori, TICRAT Poster Presentation, Alamos, Sonora, Mexico.

Chan, J. 2015.
An Investigation of the painted finishes of Mission San José de Tumacácori Façade: At the interface of materials analysis, conservation and cultural confluence, Graduate thesis, Master of Science in Historic Preservation, The University of Pennsylvania. Available at: https://repository.upenn.edu/hp_theses/573/ (accessed August 5, 2022)

Declet Diaz, N. M. 2017.
Testing and evaluation of soil-based grouts for the adhesion of consolidated and un-consolidated painted lime plaster at the Mission San José de Tumacácori, Graduate thesis, Master of Science in Historic Preservation, The University of Pennsylvania. Available at: https://repository.upenn.edu/hp_theses/619/ (accessed August 5, 2022)

Gibbs, E. and K. Wonson. 2021.
Purified linseed oil: considerations for use on historic wood. Association for Preservation Technology (APT) Bulletin, Special Issue: Wood 52 (4): 25-32.

Jang, J. and F.G. Matero. 2018.
Performance evaluation of commercial nanolime as a consolidant for friable lime-based plaster. Journal of the American Institute for Conservation 57 (3): 95-111.

Jang, J. N. Declet, J. Hinchman and F.G. Matero. 2017a.
Phase 1 report, Review of existing documentation, conservation of interior surface finishes in Mission San José de Tumacácori, unpublished report, The Center for Architectural Conservation, The University of PennsyJolvania.

Jang, J., N. Declet, J. Hinchman and F.G. Matero. 2017b.
Phase 2A report: Development of treatment plan, conservation of interior surface finishes in Mission San José de Tumacácori, unpublished report, The Center for Architectural Conservation. The University of Pennsylvania.

Jang, J. 2016.
Performance evaluation of commercial nanolime as a consolidant for friable lime-jbased plaster, Graduate thesis, Master of Science in Historic Preservation, The University of Pennsylvania. Available at: https://repository.upenn.edu/hp_theses/597/ (accessed August 5^th, 2022)

Johnson, M. and E. B. Cliver. 2002.
Coloring historic stucco: The revival of a past technique in San Juan, Puerto Rico. Association for Preservation Technology (APT) Bulletin 33 (4): 31-36.

Silva, R., L. Schueremans, D. Oliveira, K. deKoning and T. Gyssels. 2012.
On the development of unmodified mud grouts for repairing earth constructions: rheology, strength and adhesion. Materials and Structures 45: 1497-1512.

Vasquez, J. A. and M. Marcus. 2022.
Poster Presentation 2022 ICOMOS-ISCEAH Glossary of Earthen Materials Deterioration Patterns. TERRA 13^th World Congress on Earthen Architectural Heritage, Santa Fe, New Mexico.

Yang, Y. 2022.
Revisiting the past treatments and condition assessment of the painted sanctuary at Tumacácori, Graduate thesis, Master of Science in Historic Preservation, The University of Pennsylvania. Available at: https://repository.upenn.edu/hp_theses/713/ (accessed August 5, 2022)

Cite this article as:

Lim, A. B. 2025. A framework for advancing historic preservation research and education through partnership. National Park Service, Intermountain Park Science 3(1), 2025.