Specialized Committee on Earthen Architecture

• Letter from the Co-Chairs
• Reburial Research at Fort Selden
• Using Chemicals to Save Adobe
• Acrylic-modified Mud Mortars at Anasazi Sites
• Development of a Strategic Plan for Fort Union Nat'l Monument
• Conservation Program, of Earthen Plsters at Mug House, Mesa Verde National Park
• Architectural and Site Conservation at Catalhoyuk, Turkey
• Northridge Earthquake Follow-up
• Earth Slurry Seal Research
• Camp Pendleton Adobe Chapel Restoration Receives Governor's Award
• GAIA Project -- PAT 96 Course in Peru

Dear friends and colleagues:
I would like to introduce myself for those who don't know me yet. We have a couple of plans for the next year, including the beginning of a nationwide inventory of our earthen architectural heritage. We would appreciate any ideas or information you might have about this topic.

We would also like to try to get together with members of the committee to talk about plans for the future and activities you would like to be involved in. In the next months I will send you a questionnaire to find out which international conferences most of us attend in order to try to organize our first meeting. Thank you very much for your articles and support. I will continue to promote an ever-more active membership in the future.

If you have any questions or suggestions, please write me at: Maribel G. Beas, 458 Westminster Road, Wenonah, NJ 08090, e-mail address: maribelb@pobox.upenn.edu.

 

REBURIAL RESEARCH AT FORT SELDEN

The collaborative adobe research project of the Getty Conservation Institute with the Museum of New Mexico State Monuments at Fort Selden, near Las Cruces, New Mexico, will be known to many readers and further adobe research is continuing at this field testing facility. Recently, the availability of part of the site, following completion of one of the phases of adobe testing, allowed the development of a reburial research project with the active support of the Museum of New Mexico State Monuments and staff at Fort Selden. This project, being lead by Neville Agnew, Martha Demas and Charles Selwitz of the GCI, began in July 1995 with a preliminary study of reburial in test pits.

Research into reburial of archaeological sites and artifacts is urgently needed. While there is no doubt that experience at many sites þ such as at Chaco Canyon þ unequivocally has demonstrated the preservation benefits of reburial, knowledge of the exact conditions whereby artifacts may best be preserved and the technology of reburial is still lacking. We have prepared a series of "pseudo-artifacts" which have been buried under widely different defined conditions of fill materials, including soil, sand, and clay, in pits two and four feet deep, and in surface reburial as well. The burial conditions will establish wet anaerobic, and wetting and drying cycles in aerobic environments. Among these standard samples are adobe test blocks made from Ft. Selden soil, with polychromed lime plaster and adobe plaster detail molded onto opposite faces. Adobe was chosen as the inorganic test material because of its susceptibility to deterioration. Other samples include wood, cotton and wool textiles, and pieces of bronze. A principal problem of this type of research is the time frame in which one can expect to obtain results. The reburial is being accelerated by occasional wetting to achieve the most severe test conditions. We are looking for preliminary results in order to be able to refine a more definitive reburial test program. Therefore particularly susceptible materials, such as adobe, wood, and textiles, have been included in the repertoire of test samples. Environmental and subsurface monitoring is being conducted, with buried sensors for moisture, oxygen, soil temperature, via an autonomous datalogging solar powered station designed and installed by Shin Maekawa of the GCI. In addition, a variety of geo-textiles have been used in the reburial pits in order to assess their protective performance, or possible untoward side-effects. Partial re-excavation and sample evaluation against a reference set of samples will occur after 12-18 months. This will be followed by experimental refinement if necessary for longer time-scale testing.

USING CHEMICALS TO SAVE ADOBE

Chemicals can be used in a variety of ways to stabilize and protect adobe. At the Getty Conservation Institute, we have been working on three chemical procedures that can be modified and combined in different ways to address different kinds of problems affecting adobe structures. The first of the procedures involving chemicals is consolidation. Consolidation is the process where a suitable, reactive chemical in liquid form is allowed to soak into porous stone or adobe where it sets up and hardens so that the adobe is no longer turned to mud when in contact with water. The second procedure is the preparation of a modified mud by replacing part of the water mixed with sand and clay with an emulsion of an acrylic polymer in water. This amended mud can be used in a variety of ways to give more durable structures. The third tool is the use of a water repellent uniquely suitable for adobe protection to cover products of the first and second procedures.

Initially we favored Stone Strengthener H (SSH) for consolidating adobe and used it almost exclusively in our adobe research. More recently we have been working with an olgomeric form of ethyl silicate called Silbond- 40 which is a mixture of 70% condensed tetraethoxysilane, 27% uncondensed silane and 3% ethanol. Advantages over SSH include lower cost, lesser volatility and easier application, particularly in a high temperature environment. The material does not contain a catalyst such as dibutyltindilaurate, which accounts for the lower cost, but this can be added.

The second type of chemical usage is the addition of a water compatible polymer to a conventional water-clay-sand mixture in order to make a modified mud that dries to a stronger, more water-resistant adobe. This amended mud is easily made using any conventional cement mixing equipment for blending water and solids by replacing part of the water during mixing with an appropriate volume of an aqueous acrylic emulsion. The emulsions are commercially supplied at about 50% solids concentration and are diluted to from 8 to 12% of the aqueous phase on mixing. Products such as Rhoplex EC-330, Duraweld C and a Dow-Corning product packaged by a local supply house and labeled BAF (Binding Acrylic Fortifiers) and others have been used without us noting a great deal of difference.

The third use of chemicals is surface treatment with a water repellent. Particularly attractive for use with adobe are formulations based on polymethylhydrosiloxanes. Polymethylhydrosiloxanes differ from conventional methylsiloxanes, which are used for waterproofing all types of objects, in having hydrogen atoms chemically bonded directly to silicon. This is a reactive functionality which chemically combines with water to liberate hydrogen gas. When the hydrosiloxane contacts clay, this functionality creates bonding directly between adobe and the polymer and provides for exceptional stability. After treatment by spraying, the presence and the effectiveness of the polysiloxane can be demonstrated by pouring water over the treated area. The water should roll off without wetting the surface. After some time, perhaps two, three or more years, this test may show that the repellent is losing its effectiveness and it is time for a retreatment. The polymethylhydrosiloxane can be purchased as El Rey Adobe Protector as a solution in mineral spirits by the gallon or from the General Electric Company as DriFilm 1040 by the drum-load.

For preserving fragile, historic adobe walls we have combined the chemical procedures in the following way. The surface is sprayed with Silbond-40 containing catalyst at the rate of 300 ml per square foot. The tops of the walls are protected from erosion with a mounded crest of amended mud. A thin veneer of amended mud is sprayed over the entire structure and this is followed by treatment with the water repellent. As an example of the combined use of the three procedures for completely different type of adobe preservation problem, the deteriorating concrete outside plaster on the adobe Montano Store in Lincoln, NM, was replaced with a more traditional adobe covering. The concrete was ripped off, adobe bricks in some areas were stabilized with Silbond-40, the entire structure was recoated with a thick layer of polymer-amended mud and this was sprayed with water repellent when dried. After 24 months there are no signs of deterioration.

INVESTIGATION OF ACRYLIC-MODIFIED MUD MORTARS AT THREE ANASAZI SITES

The National Park Service is responsible for managing many remaining Pre- Columbian cultural sites in the Southwestern United States. There are 29 National Parks, Monuments and sites on the Colorado Plateau, in the four- corners region of Colorado, Utah, Arizona, and New Mexico. A land of dramatic contrasts in climate and geography, the mesas, mountains and plains have been home to successive periods of human habitation for thousands of years. Perhaps the most spectacular remnants of one of these cultures, the Anasazi, an ancestral pueblo people, are the remaining architecture -- cliff dwellings, pueblos and other surface sites -- made primarily of sandstone and earthen mortar.

The Conservation Program in the Intermountain Cultural Resources Center of the National Park Service and the University of Pennsylvania Architectural Conservation Laboratory, through a cooperative agreement, have sponsored several research programs directed at understanding the behavior of materials used in the field, particularly earthen materials. The Conservation Program has initiated a multi-year effort to further understand the behavior of all amendments used in mortars throughout the Plateau and the Desert Southwest parks. The pilot effort in this work is being completed by Robert Hartzler, a graduate student in Historic Preservation at Penn. He investigated the properties of mud mortar amended with the acrylic emulsion Rhoplex E-330. Three specific sites were chosen for the study: Mesa Verde National Park, in Colorado; and Aztec Ruins National Monument and Chaco Culture National Historical Park, both in New Mexico. All are Anasazi sites where polymer emulsions are used. The use of E-330 has grown significantly over the last 20 years.

Earthen mortar had at least three advantages for the Anasazi builders: it was plentiful; it required no elaborate preparation; and, when maintained, it was durable and effective in the dry Southwestern climate. At sheltered sites, original mud mortar remains in good condition almost 800 years after its installation. But in areas subject to moisture or earth movement, mud mortars can and have failed. It is the National Park Service's responsibility to maintain these sites, and often that means repairing or stabilizing original masonry, and maintaining sections reconstructed after archaeological excavation.

In an effort to make repairs similar in appearance to the original mortar yet of greater durability the National Park Service for several years has used modified mud mortars for this maintenance work. One amendment used is an acrylic emulsion, which increases particle adhesion and renders the repair mortar more durable and more resistant to water damage, thereby lengthening the maintenance cycle.

The acrylic emulsion amendment provides a more durable mortar with little change in visual appearance, and without danger to sandstone masonry risked when a hard, impermeable material such as Portland cement is added. However the perfect soil amendment still has not been found, and National Park Service has had some failures of the acrylic-modified mud mortar, resulting in premature disintegration, for reasons that are not entirely clear.

Although field tests have been conducted using acrylic emulsions and there is abundant anecdotal evidence about its performance, little laboratory work has been undertaken to help understand the interaction between the polymers and the Southwestern soils. This research project looked at some of the important variables involved in the use of this acrylic emulsion in a controlled laboratory situation and will identify some of the predictors of success and failure in the field. It is built on the important work done by Dennis Fenn, formerly of the Park Service, who introduced the idea within the Park Service of using a polymer-based mortar additive approximately 20 years ago.

Three techniques were used to gain information about the amended mortars: a search of available literature, including the work by Fenn; interviews with the stabilization crews at the selected sites to learn about success and failure in the field, and about current practices; and laboratory soil analysis and testing of manufactured acrylic-modified mortar samples. The laboratory component of this project attempted to test the most important variables in the use of amended mortar: soil type (including particle size, Atterberg limits and clay type); acrylic emulsion concentration; and weather. Tests were performed on both unmodified soils and soils modified with varying concentrations of acrylic emulsion, and included tests for water vapor transmission, strength in bending, and wetting/drying and freeze/thaw susceptibility. The final report will be completed in December 1995.

DEVELOPMENT OF A STRATEGIC PLAN FOR THE PRESERVATION OF THE ADOBE RUINS AT FORT UNION NATIONAL MONUMENT

Since its establishment as a National Monument in 1956, preservation of the adobe masonry ruins at Fort Union has challenged the National Park Service management and technical professionals. Although various stabilization techniques have been employed at Fort Union over the past 40 years to preserve the outline and form of the structures, a long-term preservation strategy that is both conservative and cost-effective has long been needed. This has become even more critical now as shrinking funds and personnel impact on the maintenance required for the preservation and management of ruins sites, and especially those of earthen construction.

Given its long history and critical role in the Service's development of ruins stabilization approaches and techniques in the American southwest, its well-documented record of existing conditions and stabilization treatments from 1956 to the present, and its unique status within the National Park system and North America as the largest adobe ruin in the country, Fort Union National Monument represents a model site for developing a long-range preservation strategy applicable to other parks with ruined masonry and earthen structures. This has already been demonstrated through the recent four-year program to design and implement conservation techniques for the stabilization of the plasters at Fort Union and Fort Davis through a cooperative agreement partnering between the Intermountain Cultural Resources Center and the University of Pennsylvania.

Park and regional correspondence of the past 30 years and the various recent NPS management plans for the site have all strongly recommended that until the characteristics and rate of deterioration of the adobe walls are understood and quantified, and the principal factors (including previous treatments) are identified, effective management of the resource will be difficult without the basic information necessary to preserve the remains in a cost-effective manner and in accordance with NPS preservation policies. A project is now underway with conservation fellows from the University of Pennsylvania to develop such a strategic plan for the short- and long-term preservation management of the adobe and masonry structures at Fort Union National Monument. This would establish an overall philosophy which would define attainable preservation goals and techniques given the nature and treatment history of the resource and the park's interpretative mandate. Fort Union's planning documents all address the need for research on the unanswered technical preservation issues. These include compilation of a database on past treatments and their evaluation; development of a monitoring program to measure the rate and amount of loss to the walls; identification of the major agents of deterioration; characterization and analysis of the adobe; and treatment research for possible inclusion in the short- and long-term preservation program for the site. This information would in turn naturally lead to the synthesis, development and implementation of an actual long-term plan of action. The project has been designed by Frank Matero (UPENN) and Jake Barrow (NPS) with Anne Oliver, Field Supervisor; and implemented by James Banta, Linnaea Dix and Robert Hartzler.

CONSERVATION PROGRAM OF EARTHEN PLASTERS AT MUG HOUSE, MESA VERDE NATIONAL PARK

From May to September 1995, The Architectural Conservation Laboratory of the University of Pennsylvania and the National Park Service/Intermountain Cultural Resources Center and Mesa Verde National Park have continued efforts in the development of a conservation master plan for the assessment and conservation of the prehistoric earthen plasters at Mug House in Mesa Verde National Park. Phase 1 of the work has been underway since the summer of 1994 with funding from the National Park Service through a cooperative agreement with the University. This initial phase included the assembly of information on past archaeological and stabilization work at the site and park, and bibliographic research on North American prehistoric plasters and mural paintings. Selected representative plaster samples from Mug House have already been analyzed to determine their micromorphology, composition and appearance using cross and thin sections microscopy, scanning electron microscopy, x-ray analysis, xray diffraction and differential thermal analysis. Phase 2, now underway, with funding from the Getty Grant Program and the National Park Service, is focused on the detailed survey and documentation of the past and existing conditions of the mortars and plasters, and the installation of an environmental monitoring program. A third phase is planned to implement a pilot conservation program based on laboratory and field testing that will ultimately lead to stabilization and presentation of these significant architectural features.

The Mug House plaster stabilization project is one of the first to develop a comprehensive, long-range conservation strategy for extant plaster in ruined sites using computer-aided documentation and a graphic conditions recording system specifically designed for plasters and architectural surface finishes. In addition to establishing a comprehensive conservation program for the park and other sites in the southwest, the investigations will bring together managers, conservators, archaeologists and architects focused on the issues of the preservation of plasters in architectural ruins and archaeological sites. Members of the team included: Kathy Fiero, Park Archaeologist; Frank Matero, Project Director; Kate Dowdy, Photodocumentation; John Fidler (English Heritage), Environmental Monitoring; Anne Oliver, Site Supervisor; Constance Silver, Mural Painting Conservator; and graduate students from the Graduate School of Fine Arts, University of Pennsylvania.

ARCHITECTURAL AND SITE CONSERVATION PROGRAM FOR THE NEOLITHIC SETTLEMENT OF CATALHOYUK, TURKEY

A phased program to develop coordinated methods for the emergency stabilization, documentation, analysis and conservation of the architectural remains, including the elaborately painted wall plasters and reliefs, at the pre-eminent Neolithic site of Catalhoyuk in southern Turkey began this year from August to October 1995. The program, designed by Constance Silver, mural paintings conservator, and Frank Matero, Director of the Architectural Conservation Laboratory, University of Pennsylvania, has been developed as a primary component of the overall archaeological excavation under the direction of Ian Hodder of Cambridge University.

Stabilization and conservation of the plain and decorated earthen plasters at Catalhoyuk have been a long-standing problem beginning with the earlier excavations at the site in the 1960s. Instability of multi-layered plasters and heterogenous or mixed media reliefs, as well as rapid drying during and after excavation, will require prepared responses based on both traditional and non-traditional approaches to the treatment of walls and painted plasters. In this regard, the author's recent technical research and conservation experience on the plain and painted mud plasters of the American southwest suggest close parallels to the materials and deterioration mechanisms at Catalhoyuk. In addition excavation requirements and the separation of multiple superimposed murals will necessitate the design and implementation of whole wall removals as well as in situ stabilization.

The site conservation program will be executed in three phases. During Phase 1, documentary research on the site's excavation and conservation history and the occurrence of plasters and related architecture fabric will be undertaken using earlier archaeological field reports to establish the extent and previous condition of the plasters from the time of excavation to the present. In conjunction with the 1995 field season, a detailed conditions survey of the excavated walls, wall plasters and paintings will be made by applying standardized nomenclature and objective recording techniques already developed by the team at other sites. Those areas determined to require immediate emergency stabilization will be treated using temporary measures and removal methods will be studied. Samples will be taken for subsequent characterization and analysis in Phase 2.

During Phase 2 work will focus on the characterization and analysis of the plasters and surface finishes, mud brick and associated architectural materials in order to determine composition and execution techniques, micromorphology and overall physico-chemical properties. Deterioration mechanisms will be studied and an environmental monitoring program will be designed for long-term assessment of site conditions. Stabilization and removal techniques will be examined and tested in the laboratory on full and half-scale facsimiles as well as on site in order to evaluate the most appropriate removal techniques and in situ stabilization options in response to the needs of the excavation program. This will be accomplished by 2 conservation graduate students as theses projects in 1995-96. Once this has been accomplished, a pilot conservation treatment program will be implemented on site during the 1996-97 field seasons as Phase 3. This program will establish the direction and goals for all future conservation at the site and will provide regional training opportunities for local and foreign participants. The summer field program will be utilized, as in previous years at other sites, to train graduate students and professionals in conservation and archaeology. This will provide a rare and invaluable opportunity for on-site experience through the implementation of the above-described program and the creation of a regional center in Anatolia. It is hoped that this program will also contribute to the overall need for greater awareness in archaeological site conservation.

NORTHRIDGE EARTHQUAKE FOLLOW-UP

The Northridge Earthquake of January 1994 seriously damaged historic adobe buildings in Los Angeles and Ventura Counties of California, including the conventos of Missions San Gabriel and San Fernando and Rancho Camulos, the "Home of Ramona," the Andres Pico Adobe and the De la Osa Adobe at Los Encinos State Historic Park.

Following the earthquake a comprehensive survey of the damage to historic adobe buildings was completed by Earthen Building Technologies (E. Leroy Tolles, Fred Webster and Edna Kimbro) and historical architect Anthony Crosby, supported by the Getty Conservation Institute. Copies of the report will be available from the Getty Conservation Institute, 4503 Glencoe Avenue, Marina del Rey CA 90292-6537.

On March 10, 1995 Earthen Building Technologies presented a workshop on Seismic Retrofit Strategies for Historic Adobe Buildings at the Getty Museum. Speakers included Anthony Crosby, Wayne Donaldson, Melvyn Green, Edna Kimbro, Michael Krakower, John Loomis, Nels Roselund, Gil Sanchez, E. Leroy Tolles, and Frederick Webster. Copies of the proceedings are available from Earthen Building Technologies 2245 E. Colorado Blvd., #104- 223, Pasadena CA 91107.

EARTH SLURRY SEAL RESEARCH

Research on "earth slurry seal" protection for unstabilized adobe architecture is being continued by the International Foundation for Earth Construction (IFEC). First reported at the Adobe 90 Symposium, this technique which employs a fluid mixture of a suitable soil with a dilute polymer latex dispersion, was applied to a new test wall in 1991.

However, several years of drought provided little opportunity for a good field test evaluation. An extremely wet winter this year showed excellent erosion resistance. The next research goal is to test on a larger structure; any suggestions would be appreciated. Also other soil types and commercial latexes will be evaluated.

IFEC is currently evaluating a new commercial silica soil that gives significant soil surface penetration. Possible combinations with calcium and aluminum compounds via a two step application method to form cementitious binders is also being investigated.

ADOBE CHAPEL RESTORED AT CAMP PENDLETON

GAIA PROJECT - PAT96
Chan Chan & Trujillo, Peru, November 10-December 13, 1996

In the framework of this program, the Instituto Nacional de Cultura del Peru - Direccion Regional La Libertad INC-DRLL) is organizing the first cycle of specialized professional training in collaboration with the International Centre for Earth Construction - École d'Architecture de Grenoble (CRATerre-EAG, Gaia Project), the International Centre for the Study of the Preservation and the Restoration of Cultural Property (ICCROM, Gaia Project), and the Getty Conservation Institute (GCI), with the support of the World Heritage Fund of UNESCO.

Aims of the Course. In accordance with the mandates and objectives of the collaborating institutions, the Pan American Course on the Conservation and Management or Earthen Architectural and Archaeological Heritage is designed to promote:

• a methodological, scientific, and interdisciplinary approach to the investigation, conservation, and management of earthen architectural and archaeological heritage;
• the development and execution of management plans befitting the specific characteristics of such heritage;
• communication between the disciplines responsible for the investigation. conservation, management of such sites; and,
• professional and institutional awareness regarding the study, conservation, and management of earthen architectural and archaeological heritage.

Description. The Pan-American Course on the Conservation and Management of Earthen Architectural and Archaeological Heritage consists of an intensive, five-week cycle of specialized professional training "in situ" at the Archaeological Zone of Chan Chan, the City of Trujillo, and other historic sites in the Moche and Chicama Valleys in the Region of La Libertad, Peru. The course is designed to respond to the specific needs of both conservators and those responsible for the management of such patrimony in the region.

The course program is structured around a core curriculum which promotes a multidisciplinary methodology for the conservation and management of earthen architectural and archaeological heritage, thereby integrating the different professions of the course participants. Specialized topics derived from the core curriculum are developed through lectures, demonstrations, practical lab and field exercises, case studies, site visits, discussions, and other such activities. The interrelated nature of these activities requires that all participants be present throughout the entire five-week period of training.

Within this comprehensive course framework, particular attention is devoted to the state of knowledge in the field of earthen architectural heritage; the problems of architectural decorative surfaces, wall paintings and polychrome reliefs on earthen supports; seismic mitigation; preventive conservation; and the development of conservation and management plans for such patrimony.

The course syllabus includes the following topics: the history and universality of earthen architecture; the earthen architectural and archaeological heritage of the Americas; decorative surfaces, wall paintings and polychrome reliefs on earthen supports; conservation history, theory, philosophy and guidelines; conservation and management planning; documentation; earthen construction technology; pathologies of earthen construction: structures, surfaces, humidity, seismic damage; survey and evaluation of conditions and context; development of conservation and management strategies; techniques for the conservation of earthen structures; techniques for the conservation of wall paintings and polychrome reliefs on earthen supports; techniques for the management of historic and archaeological sites; preventive conservation: maintenance and monitoring.

The course instructors will be specialists from the collaborating institutions and from other conservation organizations.

Participants. This course is geared toward professionals and technicians in anthropology, archaeology, architecture. engineering, conservation and other disciplines involved with the conservation and management of cultural heritage, and/or personnel with at least three years experience in the conservation and/or management of earthen historic and archaeological sites. Applicants to the course should demonstrate an active role in the programs of cultural institutions or universities in the Americas with initiatives in this field of study.

Participants will be chosen on the basis of their educational backgrounds, professional experience, and current responsibilities in the conservation and/or management of earthen sites and structures. The number of participants will be limited to 25.

Language. Spanish will be the language of the course. For those presentations and lectures given in other languages, translation into Spanish will be provided.

Venue. The venue for the course will be the Site Museum of Chan Chan (the Archaeological Zone was inscribed on the Word Heritage List in 1986 by the Convention Concerning the Protection of the Word Cultural and Natural Heritage). Ancillary activities will be hosted in the Auditorium of the Casa del Mariscal De Orbegoso (an Historic Monument of the City of Trujillo owned by INTERBANC).

Fees and Expenses. The registration fee for the course is US $1870. This subsidized fee covers the cost of registration and didactic materials, and includes lodging and meals in the City of Trujillo during the 34-day duration of the course (November 10 - December 13, 1996). Also included in the fee is the cost of local transportation between Trujillo City and the Site Museum of Chan Chan. Participants are responsible for their own travel expenses between their country of origin and Trujillo City, Peru.

Application Procedure Selection. Applicants from American countries other than Peru should submit a completed application form by December 15, 1995, to

Training Program
The Getty Conservation Institute
4503 Glencoe Avenue
Marina del Rey, California 90292
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Fax: (310) 821-9409