Adverse effects arising from conservation treatments on archaeological sites: theory, practice and review

Conservation and restoration of archaeological sites developed significantly in the second half of the twentieth century, with greater emphasis in recent decades, which has led to a considerable number of interventions. Methodology of intervention has changed significantly since more interventionist measures are performed against the current criteria of minimum intervention, although what actually occurs today is a difficult balance between innovation (experimental application of new techniques and products) and minimum intervention. The debate, in the case of archaeological sites, has focused on the actions traditionally more aggressive: cleaning, consolidation or reintegration, as this is where most notable has been the restorative action throughout history. The restoration, like everything else, has been subject of trends, in relation to the appearance of new products and technologies, and today remains a discipline that widely develops experimental practice. It certainly brings great benefits and constant renewal of criteria and methodologies, but also risks by introducing new compounds that may interact negatively with original substrate, although their effects cannot be checked in the short or medium term. The lack of knowledge of the causes of decay arising from previous interventions has generated a series of continuous protection and consolidation treatments at different periods. Restorers currently must deal with decayed areas where the products, methodology or techniques used, have caused a negative effect on the original material. This paper attempts to explore the general study of effects and alterations arising from restoration treatments, as well as reviewing of scientific publications related to this issue.series of continuous protection and consolidation treatments at different periods. Restorers currently must deal with decayed areas where the products, methodology or techniques used, have caused a negative effect on the original material. This paper attempts to explore the general study of effects and alterations arising from restoration treatments, as well as reviewing of scientific publications related to this issue.This research was supported by the PICATA fellowship program from Campus of International Excellence of Moncloa. Our acknowledgements to GEOMATERIALES programme (S2009-MAT1629/GEOMATERIALES) within Instituto de Geociencias (CSIC, UCM), to AIPA programme (ETSAM, Polytechnic University of Madrid) and to the Research Group financed by the Complutense University of Madrid "Alteration and Conservation of heritage stone materials” (ref. 921349).Peer reviewe

Effects of conservation interventions on the archaeological Roman site of Merida (Spain). Advance of research

Research on the assessment of the effects of conservation/restoration treatments on stone material has been significant in recent years, with focus on the early observation of decay caused by the application of these treatments. However, in the case of archaeological sites, research is still scarce and few studies on the subject have been published. Restoration, as everything else, has changed according to trends, mainly guided by the release of new products and technologies, an experimental field where scientific assessment of suitability, efficacy and durability pre-evaluations of treatments are not always conducted. Some efforts have been made to solve this problem in the architectural field, where functional needs and technical requirements force to set clear standards. Unfortunately, archaeological sites, unlike historic buildings, have specific features that preclude the extrapolation of these results. A critical review of the methodologies, products and restoration materials is necessary, coupled with deeper research on degradation mechanisms caused by these treatments in the mid- and long-term. The aim of this paper is to introduce the research on the above issues using Merida as a case study.Peer Reviewe

Effects of Conservation Interventions on the Archaeological Roman Site of Merida (Spain). Advance of Research

Efectos derivados de tratamientos de conservación y restauración sobre material inorgánico en yacimientos arqueológicos. Caso de estudio: Mérida

Piedras artificiales: morteros y hormigones. El cemento como máximo representante de estos materiales de construcción

12 págs, 7 fig.-- Publicado en el libro "Ciencia, Tecnología y Sociedad" dentro del programa Maternas financiado por la Comunidad de Madrid, en colaboración con la Asociación Restauradores sin Fronteras (RSF).[EN] From the dawn of architecture to the present day, artificial stones have been the most in-demand building material. Natural stones, because of their beauty, fine quality, etc., are now favoured over artificial stones, but the use of the latter has always been indispensable. The most representative group of artificial stones is that of mortars and concrete. These mortars are obtained from the mixture of natural dry materials with a binding material and water. The binding materials may be common (lime, plaster, clay, etc) or hydraulic (hydraulic lime and cements). Over the last two centuries, 19th and 20th, the prominence of hydraulic mortars and concrete has been enormous and has given cement the starring role in modern construction.[ES] Desde los albores de la arquitectura y hasta el día de hoy, piedras artificiales han sido las más demandadas dentro de los materiales de construcción. Las piedras naturales, debido a su belleza, gran calidad, etc, han sido mejor valoradas que las piedras artificiales, pero el uso de estas últimas siempre ha sido indispensable. El grupo más representativo de piedras artificiales es el de los morteros y hormignones. Estos morteros se obtienen a partir de la mezcla de un árido natural seco con un aglomerante y agua. Los aglomerantes pueden ser de materiales comunes (cal, yeso, arcilla, etc) o hidráulicos (cal hidráulica y cementos). En los últimos dos siglos, XIX y XX, la utilización de morteros hidráulicos y hormigones ha ido en aumento, lo que implica que el cemento juega un papel importante en la construcción moderna.Proyecto Maternas financiado por la Comunidad de Madrid (Referencia S-0505/MAT-0094)

Non-destructive testing for the assessment of granite decay in heritage structures compared to quarry stone

Several types of granite found in two architectural heritage monuments were assessed with two non-destructive, portable techniques: Schmidt hammer rebound and ultrasound velocity (Vp). Similar assessments were conducted on the rock from which the granite was originally quarried for comparison. The results obtained, which revealed the existence of a direct correlation, constitute a useful indication of decay, particularly if the approximate dates of construction are known. And conversely, if they are not, such stone assessments may provide a rough estimate of when the structure was built. Both of these convenient, portable and non-destructive techniques may be used as reliable indicators of the degree of stone decay

The measurement of surface roughness to determine the suitability of different methods for stone cleaning

Trabajo presentado a la EGU General Assembly 2011.In order to select the best bead blasting based method to clean the stone masonry of specific areas of the Cathedral of Segovia (Segovia, Spain), measurements of the roughness of the stone surface were performed, before and after cleaning processes.Peer reviewe

Evaluación de tecnicas de limpieza y desalinización en la catedral de Segovia, España

Los materiales pétreos (naturales o artificiales) utilizados en la construcción del patrimonio cultural se ven afectados por procesos de cristalización de sales que conducen a una pérdida de compacidad y cohesión del material. Cuando se observan sales en la superficie de un muro pétreo el problema es que existan también en el interior, bajo la superficie, por lo cual lo realmente importante es saber la extensión de estos procesos en el interior de los muros. En este trabajo se presenta una metodología basada en análisis mediante cromatografía iónica de muy pequeñas cantidades de muestras a diferentes alturas de un muro y a diferentes profundidades. Por otro lado, son numerosos y muy variados los métodos de limpieza que se utilizan hoy en día en el patrimonio construido. Se presenta a este respecto una metodología para la evaluación de la eficacia de cualquier sistema de limpieza mediante la combinación de varias técnicas, dos de ellas no destructivas – medida del color mediante espectrofotómetro, y de la rugosidad mediante rugosímetro superficial 3D, junto con el uso de la microscopía electrónica de barrido (MEB/SEM) y el microanálisis por dispersión de energías de rayos X (EDX)

Control térmico de la meteorización de superficies endurecidas en rocas graníticas (La Pedriza de Manzanares, España)

[ES] La Pedriza de Manzanares es parte del Parque Nacional del Guadarrama en el Sistema Central Español. Se caracteriza por formar un paisaje laberíntico constituido por una alternancia de bloques y grandes paredes de granito. Gran parte de las superficies de estas rocas están recubiertas por costras endurecidas de espesores milimétricos, que controlan la alteración superficial y favorecen el desarrollo y distribución de micro-relieves sobre las paredes. Para explicar el proceso de alteración que favorece la formación de irregularidades sobre la superficie del granito, en este trabajo se analizan algunas variables tales como la temperatura, índice de esclerometría y morfología de los micro-relieves. Por otra parte, el artículo establece relaciones entre la primera fase de formación de las superficies endurecidas en condiciones subedáficas, asociada al frente de alteración, con los espesores de las costras endurecidas y la erosión del regolito. Las relaciones definidas y resultados obtenidos son de aplicación en otras regiones graníticas del mundo de características similares.[EN] Pedriza de Manzanares is part of the Guadarrama National Park in the Spanish Central System. It is characterized by a labyrinthine landscape composed of alternating blocks and large walls of granite. Case-hardened crusts of millimetric thickness covering most of these rock surfaces control the surface alteration and favor the development and distribution of micro-reliefs on the walls. Some variables such as temperature, sclerometric index and micro-relief morphology are analyzed in this paper in order to explain the destructive process of alteration that favors the formation of irregularities on the granite surface. On the other hand, the paper establishes the relation between the first stage of case-hardening in sub-edaphic conditions, which is associated with the alteration front, and the thickness of such crusts and regolith erosion. These results can be applied to other granitic regions with similar characteristics all over the world.Peer reviewe

Changes in Petrophysical Properties of the Stone Surface due to Past Conservation Treatments in Archaeological Sites of Merida (Spain)

Petrophysical properties, such as porosity, permeability, density or anisotropy de-termine the alterability of stone surfaces from archaeological sites, and therefore, the future preservation of the material. Others, like superficial roughness or color, may point out changes due to alteration processes, natural or man-induced, for ex-ample, by conservation treatments. The application of conservation treatments may vary some of these properties forcing the stone surface to a re-adaptation to the new conditions, which could generate new processes of deterioration. In this study changes resulting from the application of consolidating and hydrophobic treatments on stone materials from the Roman Theatre (marble and granite) and the Mitreo’s House (mural painting and mosaics), both archaeological sites from Merida (Spain), are analyzed. The use of portable field devices allows us to perform analyses both on site and in la-boratory, comparing treated and untreated samples. Treatments consisted of syn-thetic resins, consolidating (such as tetraethoxysilane TEOS) and hydrophobic products. Results confirm that undesirable changes may occur, with consequences ranging from purely aesthetic variations to physical, chemical and mechanical damages. This also permits us to check limitations in the use of these techniques for the evaluation of conservation treatments

El patrimonio arquitectónico de Boadilla del Monte: el Palacio del Infante don Luis de Borbón y el Convento de la Encarnación

Con motivo de las actividades realizadas durante la III Semana de la Ciencia (2003), el grupo de investigación Petrología Aplicada a la Conservación del Patrimonio del Instituto de Geología Económica (IGE-CSIC/UCM), realizó una Ruta Geomonumental mostrando los materiales pétreos empleados en el patrimonio construido de Boadilla del Monte (Madrid), principalmente en el Palacio del Infante Don Luis de Borbón. Este tipo de recorridos representan una metodología novedosa para la divulgación del patrimonio arquitectónico y monumental desde el punto de vista de los materiales geológicos que lo configuran. El prefijo “Geo” indica el fuerte condicionante geológico que tradicionalmente ha influido en los asentamientos urbanos y en su desarrollo, así como la relación existente entre la arquitectura y la geología, puesto que gran parte de los materiales de construcción se extraen de la tierra. Los materiales pétreos empleados en la construcción del palacio son el ladrillo (originales y de restauración), los morteros (revestimientos y morteros de junta) y la piedra natural (granito y caliza). Los ladrillos originales presentan un avanzado estado de deterioro, estando afectados por procesos de fisuración, arenización o pulverización. Los revestimientos principalmente muestran humedades, descamados y desprendimientos. El granito, procedente de las canteras de Valdemorillo-Zarzalejo, sufre importante procesos de fisuración y arenización. La caliza, extraída en las canteras de Colmenar de Oreja, presenta en general buen estado de conservación. [ABSTRACT] Due to the activities performed during the Third Week of Science (2003), the Applied Petrology for Heritage Conservation Research Group, belonging to the Economic Geology Institute (IGE-CSIC/UCM), carried out a Geomonumental Route where the stone materials used in the built heritage of Boadilla del Monte (Madrid), mainly in the Palacio del Infante Don Luis de Borbón, were shown. The Geomonumental Routes account a different methodology for the cultural and scientific dissemination of built heritage, from the viewpoint of the stone materials, natural and artificial, that shape it. The prefix "Geo" tackles the landscape strongly influences in settlements and their development, and it establishes the relationship between historical sites and geology as well, in the sense that the main resources for building are extracted from the earth. Besides, the behaviour and decay of building materials is hardly influenced by its surrounded environment. The stone materials used at the construction of the palace are brick (original and restored), mortars (coatings and joint mortars) and natural stone (granite and limestone). The original bricks show an advanced state of decay, being affected by processes of cracking and surface pulverization. The coatings mainly suffer dampness, peeling and flaking. The granite, from the quarries of Valdemorillo-Zarzalejo, presents major cracking and surface pulverization processes. Limestone, extracted in the quarries of Colmenar de Oreja, generally displays a state of conservation quiet good