Paper 4: Mechanical Properties of Bricks of the Coudenberg Archaeological Site in View of a Proper Conservation Strategy

Abstract

Archaeological sites are essentially submitted to decay phenomena inherent on their history as well as the environment to which they are exposed after excavation. The history of such archaeological sites is particularly related to their long-term underground conservation conditions during which they were subject to salt migration into the architectural remains. This paper describes the results of drill resistance measurements using a drill resistance measurement (DRMS) device to evaluate the mechanical damage resulting from salt crystallization pressures. Further tetraethoxysilane (TEOS) was applied on powdered bricks of often moist archaeological remains. It was noticed that TEOS serves as potential nutrient for present moulds. The mechanical consolidation effect was evaluated by comparing the hardness profiles after treatment with the reference ones. Bricks used for the construction of the Aula Magna, situated underneath the Royal Square, are characterized by severe patterns of fissures for which the damage diagnosis was built up.     

Paper 3: Impact of the Indoor Climate on the Performance of Building Materials Contaminated with Salt Mixtures

Abstract

Archaeological sites are essentially submitted to decay phenomena inherent on their history as well as the environment to which they are exposed after excavation. The history of such archaeological sites is particularly related to their long-term underground conservation conditions during which they were subject to salt migration into the architectural remains.

It is well known that soluble salts present in building materials can cause damage, mainly by producing stresses in the substrate. A lot of research has been done in the past concerning the behaviour of salts in built constructions. However, most studies include single salts, of which the deliquescence points are well documented, while in situ one mostly finds complex salt mixtures, which makes the conservation strategy much more intricate.

The environmental conditions to minimize damage of salt-laden porous building materials can be modelled using a computer program ECOS capable of predicting the crystallization behaviour of salt mixtures. To use the model data of quantitative salt analyses are required as input. The program is then able to predict from a thermodynamic point of view which minerals will exist in the solid state under specified climatic conditions.

This paper deals with the results of a systematic investigation of the salt contamination of the building materials of the Coudenberg site and a prediction of the behaviour of the salt mixture related to the actual climate, as part of the environmental assessment.     

Managing for Effective Archaeological Conservation: The Example of Salisbury Plain Military Training Area,England

Abstract

Salisbury Plain Military Training Area, Wiltshire, England is the major zone of southern Engizsh chalk downland where archaeological field monuments are comparatively well preserved over large areas. The land is currently managed with regard to military considerations, to its secondary use for forming, and to conservation concerns. Following expressions of concern about archaeological damage, a working party was set up to evaluate the present state of archaeological survival and to recommend for the future. A survey of all sites evaluated their condition by means of a scoring system. Recommendations were made about military use, agriculture, and controlling natural agencies of destruction; and a solution was offered that incorporated eight elements of strategy. The Salisbury Plain study is considered in its context—the English national policy that there should be an archaeological stock-taking of what we have, and a scoring system to make possible some rational choice in selecting from it what is most precious and what is in most need of protection.     

The Feathered Serpent Pyramid at Teotihuacan: decay,conservation and future perspectives

Abstract

The Feathered Serpent Pyramid at Teotihuacan, Mexico, is one of the most outstanding monuments of Mexican archaeological heritage. However, the volcanic stones that constitute the main façade of this building are subject to complex deterioration phenomena that include decay caused by the presence of water and soluble salts, as well as inappropriate treatments carried out in past decades. Agents of decay are explained in the article, as well as the means of diagnosis employed for their study. Recent conservation activities and other potential conservation treatments are also discussed.     

基于环境监测的三星堆遗址祭祀坑考古现场预防性保护

目前考古现场保护主要以应急保护技术与临时加固材料的研究和应用为主,而关于考古现场预防性保护少有报道。本次三星堆遗址祭祀坑发掘保护构建了由考古舱、考古舱环境调控系统、空气质量监测系统、土遗址监测系统、区域气象站、预防性保护措施、监测信息智能管理平台组成的预防性保护体系。发掘前,通过土遗址监测系统和区域气象站获取文物埋藏环境信息和区域气象信息,为考古舱内环境设置提供了依据。发掘过程中,采取舱内温湿度调控、保湿、空气杀菌净化、控制舱内人数与新风换气等预防性保护措施,达到控制考古舱温湿度、减少细菌和真菌总数、降低舱内CO_(2)浓度,减缓象牙等文物失水速度的目的,有效控制了出土文物开裂、酥粉、霉菌暴发等病害发生,为考古发掘与保护赢得了时间。三星堆祭祀坑考古现场预防性保护的创新探索与实践为以后重要遗址的现场保护指引了方向、提供了可借鉴经验。     

Paper 2: Climatic Study of the Underground Archaeological Site Coudenberg

Abstract

The excavation and valorization of subterranean archaeological remains, and eventually opening a site to the public, required a proper management and conservation strategy. This strategy was based on the evaluation of the delicate balance between the requirements for public health and safety, and the protection of the archaeological remains from future degradation. Controlling the climate can be essential for a preventive conservation strategy, which can be defined as an indirect action to increase the life expectancy of the archaeological remains, and by doing so keeping them in a preferred state of conservation to mitigate damage and/or deterioration.

Potential risks and possible interventions are outlined to avoid climatic conditions which are in conflict with the requirements for the visitors’ comfort while preventing damage phenomena to the materials.     

THE WRITING'S IN THE WALL: A REVIEW OF NEW PRELIMINARY APPLICATIONS OF ELECTRICAL RESISTIVITY TOMOGRAPHY WITHIN ARCHAEOLOGY

Natural processes are known to cause significant damage to archaeological monuments. In fact, the key to understanding the decay of building materials is the internal movement of water through the mineral matrix, which influences the distribution of chemical, physical and biological deterioration processes. Electrical resistivity tomography (ERT) was traditionally used as a surveying tool within archaeology, but a new high‐resolution technique that accurately traces the movement of moisture in building materials could provide a vital tool for understanding the decay of many archaeological monuments. This paper considers current progress, the shift of ERT from soil to rock research and the impact that this development could have on future conservation, using Hertford College (Oxford) and Neolithic rock art (Golden Gate Reserve, South Africa) as case studies.     

Damage or protection? The role of smoked crust on sandstones from Yungang Grottoes

Black crusts, such as dust deposit and smoked smudge, are the main pollutants in Yungang Grottoes, the world famous Buddhist heritage site. It is always considered that the black crust should be removed during the conservation process of stones. In this paper, the investigation of the role of smoked crust on the Yungang sandstones was performed to verify if the smoked layer on the stone surface would be harmful or protective. The results of SO₂ corrosion experiments with and without water both show that the samples covered with smoked layer can play a protective role on the sandstones, which means that the smoked layer on the stones can prevent the attack of SO₂ and water, the major deterioration agents in Yungang area. The multi-factor deterioration cycle experiments, including salt crystallization, freeze–thaw damage, wet–dry cycle and acid corrosion, also indicate that the smoked samples are less deteriorated and salt crystallization is the most severe damage to the sandstones.     

Salt Effects in Plastered and Unplastered Outdoors Brick Masonry: Quantitative Laser Monitoring of Surface Decay Evolution

In masonry materials, the superficial decay is a widespread problem. Aggressive environmental agents such as moisture and salts trigger the damage by propagating through the material capillary pores. Although several studies have been carried out on salt crystallization and their damaging effects, additional research effort is required to better investigate this phenomenon on real cases and real weathering conditions. To this purpose, testing and monitoring tools capable of following degradation process since the early beginning are necessary. Repeated visual inspections are commonly used to monitor the superficial decay, but this technique is subjective and thus not capable of providing any quantitative information. In this work, an experimental campaign, carried out in Bologna, Italy, is presented. A two-header brick wall, one main face unplastered and one plastered, was stored outdoors and exposed to weathering over two summers. Before the start of the second aging season, moisture and salt capillary rise was simulated by low-concentrated sodium chloride solution (0.1% -wt). The aim was to favor solution evaporation and salt crystallization and to provoke material damage. The degradation process was monitored based on a contactless, rapid and accurate image diagnostic technique. In particular, high-resolution laser scanning by triangulation technique was adopted. Three-dimensional data acquisition was repeated at the end of both seasons. The proposed procedure successfully extracted quantitative information approximately areas of material spalling and detachment even in the initial phases of decay.     

Microclimate and Salt Crystallization in the Crypt of Lecce’s Duomo

Ancient masonry structures are often damaged by soluble salt crystallization, which is activated by even small microclimatic variations. Unsuitable environmental conditions can accelerate this process, affecting the type and the quantity of salts and the consequent damage to the masonry. Therefore the importance of monitoring salt diffusion to control salt crystallization and microclimate over time is widely recognized. This study proposes an integrated monitoring methodology to obtain information on the relationship between salt efflorescence and microclimate in the Crypt of the Duomo of Lecce (South Italy). By combining ion chromatography, powder X-ray diffraction analysis, and Raman microscopy with environmental monitoring and deterioration maps, salt components were identified and efflorescence diffusion on masonry was monitored over time. Due to this approach, a possible explanation for the process is finally given.     

An assessment of the value of bone density measurements to archaeoichthyological studies

This paper reviews the meaning of the term ‘density’ and the problems associated with the methods of density determination for animal bones in archaeology. It has often been assumed that density is the intrinsic property of most influence in controlling the rate of a bone's decay. Values for whole bone density have been published only for large mammal bone, however. Fish bone appears to be particularly vulnerable to decay, and usually a restricted range of skeletal elements are recovered from archaeological sites. The object of this study was to examine the relationship between fish bone density and the ability of the bone to survive on occupation sites and in archaeological deposits. A set of ‘density’ measurements was established for the bones of cod (Gadus morhua). The usefulness of these measurements as a predictive tool in archaeoichthyological studies is assessed. It was found that ‘density’ as measured did not explain adequately the relative survival of skeletal elements after mechanical abrasion and weathering, or within archaeological deposits.     

海洋出水木质文物保护中的硫铁化合物问题

海洋出水的木质文物中通常会沉积硫铁化合物。打捞出水后,硫铁化合物遇到空气和水分后会发生氧化,生成硫酸以及各种硫酸盐,并引起有机质的降解。近年来,硫铁化合物对海洋出水木质文物的危害已引起广泛关注。为此,本工作阐述了硫铁化合物相关问题的研究现状,就硫铁化合物的产生原因、危害以及目前控制方法的研究进展进行了总结,同时评述了针对硫铁化合物的处理方法。     

NO STONE UNBURNED: A COMPOSITIONAL ANALYSIS OF OBSIDIAN MICRODEBITAGE BY LASER ABLATION TOF–ICP–MS

Obsidian is an effective material for the study of prehistoric raw material use and exchange, due to the high degree of homogeneity and redundancy of obsidian materials and manufactured objects in the archaeological record. The destructive nature of many analytical techniques often impedes compositional research because of the damage that may occur to priceless archaeological artefacts. The combination of time‐of‐flight (TOF) ICP–MS with a laser ablation sample introduction system provides a highly efficient means of chemically characterizing obsidian. This study shows that sample size limit capabilities of TOF–ICP–MS analysis of obsidian can reach less than 100 μm. Sampling and analysis of microartefacts enables researchers to overcome problems of sampling bias with very little damage to the valuable existing materials within the archaeological record and expands the potential for chemical compositional analyses in archaeology.     

Characterization and damage assessment of stones used in the Pasargadae World Heritage Site,Achaemenian period

The architectural remains at Pasargadae were built of three different stones classified according to their colors (beige, dark-gray, and green-gray). The stones show different macroscopic features, such as texture and decay patterns. The aim of this study is to identify the composition of the stones and to evaluate the main decay factors through petrographic studies in order to make conservation decisions more compatible. Petrochemical analyses show that the stones are in fact limestones with different features; two of them have a compact texture (beige and dark-gray stones), while the third has a fairly porous structure (green-gray stone). In some beige stone samples, dolomite was identified. Despite the fact that the presence of salt is a possible decay factor, X-ray diffraction analysis did not report any salt. According to SEM observations, the main reasons for decay in dark-gray and green-gray stones are the dissolution of calcite crystals and the swelling of clay minerals. The main decay factor in the beige stone, by contrast, is dissolution induced by microorganism activity. However, a patina formed by lichens on the surface of the beige stone, although aesthetically detrimental, protects it against further decay.     

The Tenth Conference of the International Committee for the Conservation of Mosaics. Conservation: An Act of Discovery

Abstract

The Herculaneum Conservation Project has approached the conservation of a large-scale archaeological site (Herculaneum, Italy) suffering widespread forms of decay in two different ways: 1) with a site-wide campaign addressing conservation problems in areas most at risk and 2) with a case-study project for one urban block (Insula Orientalis I ) exploring some of the complex conservation challenges in more detail. One of these challenges is how to approach the repair of existing roofing and how to design new forms of protective shelter for those spaces that have never been covered. Short-, mid- and long-term solutions for the repair and substitution of existing roofing are being tested as part of the site-wide campaign, while in the case-study area more enduring solutions (new mid- and long-term) for new shelters are being trialled.     

Research and Monitoring on Conservation State and Preservation Conditions in Unsaturated Archaeological Deposits of a Medieval Farm Mound in Troms and a Late Stone Age Midden in Finnmark,Northern Norway

This paper presents archaeological observations and results of palaeoecological and geo-chemical analyses of archaeological deposits from two rural sites in northernmost Norway. These are combined with climate data and the first period of continuous monitoring of soil temperature, moisture, and redox potential in sections. This data constitutes the basic research material for evaluations of conservation state and preservation conditions. The data has been collected in collaboration with the partners of a cross-disciplinary project: ‘Archaeological Deposits in a Changing Climate. In situ Preservation of Farm Mounds in Northern Norway’ funded by the Norwegian Council for Research (http://www.niku.no/en/archaeology/environmental_monitoring/archaeological_deposits_in_a_changing_climate_in_situ_preservation_of_farm_mounds/). This is an important Norwegian research initiative on monitoring of rural archaeological deposits, and the results have consequences for heritage management of a large number of sites from all periods. Palaeoecological analyses and redox measurements have revealed ongoing decay that might not otherwise have been detected. Decay studies indicate that both site types may be at risk with the predicted climate change. Some mitigating acts are suggested.     

Moisture content measurement and surface water absorption test in the inner gallery of Bayon for the conservation of the bas-relief

The bas-relief carved on the sandstone wall in the central part of the inner gallery of Bayon in the Angkor monuments, Cambodia, has been severely damaged mainly due to calcite crystallization. In order to confirm the mechanism of salt weathering and help determine conservation measures for the bas-relief, measurements of the annual change in the moisture content in the bas-relief were conducted. We found that water supplied from the platform behind the bas-relief is the cause of calcite crystallization. It is therefore indispensable for the conservation of the bas-relief to prevent the water permeating from the inside of the platform behind it. As precipitated calcite from the water block pores near the surface of the sandstone, the surface water absorption test is a useful method to evaluate the degree of the salt weathering.     

Remains of the day-preservation of organic micro-residues on stone tools

Here I report on the decay processes of microscopic organic residues left on stone tool surfaces after their use. Residue analysis on ancient stone tools facilitates reconstruction of past activities. This study enables predictions about the circumstances under which ancient residues preserve. Experimental tool sets with modern residues were buried for a year in separate deposits at Sterkfontein, Sibudu (South Africa) and Zelhem (the Netherlands) whose pH and geomorphology varied, they were then analysed using light microscopy. Biological weathering mainly causes residue decay. In unstable environments rich in microbes and micro-organisms, residues decay quickly. From an archaeological perspective this means that sites that are stable, desiccated, waterlogged, extremely acidic or alkaline and extremely cold or hot sites. Different residue types have different preservation optima and this may lead to a preservation and perhaps interpretation bias. The preliminary predictive models presented in this paper could aid in the considered selection of sites and samples.     

饱水木质文物的细菌病害及其诊断技术的进展

为了促进微生物学理论与技术在我国文物保护领域中的应用,使我国的文物保护与国际先进水平接轨,本文通过对国内外有关文物保护微生物学研究进展的综述,阐述了饱水木质文物细菌性病害的成因和机理.侵蚀细菌、钻管细菌和空化细菌是饱水木质文物细菌性病害的病原体,但它们的作用方式有一定的区别.在饱水木质文物细菌性病害诊断上,国外已较为普遍地使用了光镜技术、电镜技术、细菌培养技术以及多种分子生物学技术.根据众多样本分析的结果,国外学者已建立评价饱水木质文物腐蚀状态的定性指标体系.文中还结合目前我国有关饱水木质文物保护的现状,阐述了文物保护微生物学在我国饱水木质文物保护中的应用前景,并建议尽快开展相关的研究工作.     

A botanical approach to the planning of archaeological,parks in Italy

Abstract

The positive role of plants in archaeological areas, as well as the enegative action of their roots in causing structural damage, are summarized in this paper. The traditional approach to the planning of vegetation in Italian archaeological areas is briefly described. A general philosophy for botanical projects in these sites is proposed, taking into account ecological, historical and conservation parameters. The principal aims of the suggested approach are: protection of the naturalistic, historical and landscape features of the existing site, in so far as they are compatible with the archaeological structures; and the introduction of new elements, in keeping with the original landscape, which exploit shelter effects or improve microclimatic and soil characteristics, and are also ‘ornamental’. The criteria for evaluating the characteristics of the site from the naturalistic and from the historical and landscaping points of view are explained. Also briefly. discussed, are congruity with the history and character of the site, overall compatibility with archaeological structures, usefulness for reconstructing specific environments, conservation Value for the site and aesthetic and economic criteria for the selection of species to introduce.