Roman bricks from the Lagoon of Venice: a chemical characterization with methods of multivariate analysis

From 18 archaeological sites of the Lagoon of Venice 75 bricks belonging to Roman and medieval building levels have been analysed. Chemical composition and geometric measures allow the characterization of a group of 24 Roman bricks of Imperial age. The group formed by means of fuzzy c-means cluster analysis applied on chemical data have been tested by principal component analysis and finally subjected to discriminant analysis to estimate the relative weights of original variables and classify new elements. Correlations among the data of the major chemical elements confirm the reliability of the complex of chemical data. The aim of this research was to obtain a chemical characterization of Roman bricks (and later, of the medieval ones) coming from the lagoon of Venice thus making it possible: 1) to recognize the age of a brick by means of its chemical analysis; 2) to date the layers of archaeological excavations or the ground where there are medieval building foundations by means of membership bricks; 3) to calculate the rate of local ground lowering in the elapsed years by the difference in level from one layer to another; 4) to estimate local rates of land subsidence by comparison with mean values already known.     

Survey of decay of tezone ‘105’: methodology for acquisition of data

Within the multidisciplinary study concerning one of the covered dockyards (called tezone 105) erected in the Arsenal of Venice, carried out by the ‘Target Venezia’ CNR Project, it will be presented here a preliminary work concerning the survey of decay¹. This analysis is strictly connected with the other works carried out by the Operative Units of the ‘Target Venezia’, especially with the stratigraphical survey² and the chemical and microstructural characterisation of mortars³ and bricks⁴. First, the survey of decay has been based on the stratigraphical investigations of the tezone structure, which has allowed the classification of the different building phases over a long period (from the XVI until the first half of the XX century). Second, a computer aided methodology has been applied in order to make the research easier and to allow multiple queries either to know which kind of decay are present in every point of the surfaces and the global extension of each typology of degradation⁵.     

Damage on hydraulic mortars: the Venice Arsenal

Very few scientific studies have been performed so far on ancient and modern hydraulic mortars. The effects of atmospheric multi-pollutants on hydraulic mortars used in monuments and historic buildings in urban areas, especially those linked to dry and wet carbon and sulphur deposition, remain in need of thorough investigation. In the literature, studies on damage typology identification, composition and origin and relative quantitative data are both scarce and rather poor in quality. While the sulphate source from marine spray deposition and water capillary rising are known, atmospheric sulphur effects on mortars still require elucidation. Ancient and modern hydraulic mortars have been collected from the Arsenal of Venice. The original material characterisation and the evaluation of the surface damage due to atmospheric pollution are presented along with a comparison of the data obtained for the cement and cocciopesto mortars.     

Characterization of binders employed in the manufacture of Venetian historical mortars

This research focuses on the characterization of historical mortars collected from a covered dockyard, called tezone 105, erected in the Arsenal of Venice during the XVI century. The mortars date back to different building phases. A stratigraphical analysis of tezone 105 has proposed a chronology of building interventions. The building phases recognized by the stratigraphical analysis belong to the original structure (XVI century) and to later interventions from XVI to XX century. Mortar samples are investigated by granulometric analysis, infrared spectroscopy (FT-IR), simultaneous thermal analysis (DSC/TG) and X-ray diffraction analysis (XRD) in order to identify the technology peculiar of each building phase. Mortar sampling was carried out on indoor masonry and foundation. Masonry mortars appeared to be characterized by the application of air-hardening binders, whereas foundation mortars were characterized by hydraulic binders.     

A color image segmentation method as used in the study of ancient monument decay

In the cultural heritage area, it is of fundamental importance to characterize and classify the conservation state of the materials constituting ancient monuments, in order to study and monitor their decay. Generally, the decay diagnosis is provided by “naked eye” analysis done by expert scientists “walking around” the artifact and recording the conservation state of each individual element they observe. In this paper, a color image segmentation approach, based on histogram threshold and edge detection techniques is presented, to extract degradation regions, characterized by holes or cavities, from color images of stone-materials. The goal is to provide an aid to the decay diagnosis by segmenting degraded regions from color images, computing quantitative data, such as the area and perimeter of the extracted zones, and processing qualitative information, such as various levels of depth detected into the same zones. Since color is a powerful tool in the distinction between objects, a segmentation technique based on color, instead of intensity only, has been used to provide a clearer discrimination between regions. The study case concerns the impressive remains of the Roman Theatre in the city of Aosta (Italy). In particular, we have processed and analyzed some color images of the theatre puddingstones, acquired by a camera.     

基于数字技术的历史街区空间更新与文化价值活化设计 ——以南京南捕厅历史街区为例

以南京市南捕厅历史街区为例,通过综合运用三维地理信息系统、多元异构时空数据分析、历史信息比对等技术手段,展示了复合历史空间导向的数字化保护与更新实践.通过无人机倾斜摄影测量技术,对历史街区的大场景进行纹理数据采集,构建整个历史街区的三维数据模型.在历史研究的基础上,为历史街区更新构建合理的历史空间形态框架,并对历史街巷...     

Determination of the impregnation depth of siloxanes and ethylsilicates in porous material by neutron radiography

For conservation of the built cultural heritage, the application of conservation products like consolidants or water repellents is often suggested. Their impregnation depth is a key factor for the assessment of the treatment efficiency. It will vary depending on the internal structure of the stone material and the properties of the conservation products. In this study a porous bioclastic limestone from Maastricht (the Netherlands) and a porous sandstone of Bray (Belgium) were selected for treatment with either ethylsilicate-based consolidant products or siloxane-based water repellents. We explore the potential of neutron radiography to visualize the conservation products after polymerization, since previous experiments already proved their detectability before polymerization. Additionally, water absorption by capillarity was monitored inside the samples. The experiments in this study illustrate that the ethylsilicate-based consolidants remained visible for neutrons even after the polymerization process, while the siloxane-based water repellents can only clearly be distinguished in the stone as long as they contain a certain amount of solvent. The study proves that neutron radiography can provide important additional information for the research in the built cultural heritage domain, especially as it allows to successfully visualize the impregnation depth of silicate-based consolidants inside natural building stones.     

A new approach for conservation treatment of a silk textile in Islamic Art Museum, Cairo

The paper presents strategies for the conservation of historical textiles in Egypt that have been in uncontrolled storage and display. The silk textile is highly decorated, multicoloured and dates to the Ottoman period, and was exhibited in case # 12014. The textile has various types of deterioration. An examination and analysis of the textile was undertaken in order to develop a plan of conservation treatment. FTIR was used to identify the kinds of dyes and organic stains, and XR-D was used to identify mordants and dust. Light microscope and SEM were used to identify the kind of fibers, their condition and surface morphology. The effects of cleaning materials on the natural dyes were tested. The researcher designed a new metallic frame support system which has advantages over the wooden frames commonly used in Egypt. This presentation will review the conservation treatment step by step. Poultices were used to remove all the sticking cardboard and adhesive. Old conservation repairs were removed. Separated parts were supported. Cleaning included mechanical and wet cleaning. New silk fabrics dyed with natural dyes were used to complete the missing parts. The textile was supported on new linen fabric which was stretched on a metal frame. The method of exhibition will be discussed. Photographs are included to document the conservation process.     

Material structure and constructive history

The features of materials and of constructive techniques have been singled out and recorded through techniques already experimented in the archaeological field (stratigraphy and typologies comparisons); it led to determining the constructive history, the alterations and the restorations of the building on a wide scale which goes from the margin walling of the Arsenal to the colours of walls. Every single piece of the building can be associated to the general constructive history and can be representative of the whole body of materials and constructive techniques used in the different historical periods of construction and use of tesone 105.     

A spectral imaging methodology for determining on-line the optimum cleaning level of stonework

This study aims to introduce a new spectral imaging methodology that can be used to monitor on-line, non-destructively and in situ the cleaning level of pollution encrustation on stonework. The suggested technique is based on the optical properties of monochromatic light penetration in matter. The calculated differences of images, obtained at two different spectral bands, could reliably map the depth of cleaning. This novel approach was tested in the laboratory during laser cleaning trials on polluted stonework enabling high accuracy measurements (such as the detection of thin crust layers remaining on the under-cleaned marble surfaces). However, it may also apply for the monitoring of any other cleaning technique (micro air-abrasive, etc). A detailed presentation of the results will be demonstrated while the potential of its wide application on everyday conservation practice on stonework will be discussed.     

Identification and assessment of engineered road heritage: A methodological approach

Roads built by civil or military engineers from the 18th century onwards form an essential part of our heritage, but currently considered on a very infrequent basis. They represent one of the main turning points in the development of the transport system and serve to gain a better understanding of the historic construction of many landscapes and their current arrangement and operation. Their consideration as heritage has to be made on a territorial scale. This approach regards landscape as a cultural artifact, which is undergoing constant design, construction and transformation, where the road is considered as an axis that shapes the landscape and that contains individual elements such as associated structures or buildings. One of the most important characteristics of historic roads undoubtedly lies in the fact that they are a heritage that is still in use. Many of the roads built for carriages or the first automobiles have, in fact, served to trace the current network of roads and motorways. For this reason, many historic routes have undergone considerable modification and a large percentage of their heritage has disappeared. Likewise, their original or more intact sections, that is to say those that were replaced during their gradual adaptation to the automobile in the 20th century, are not always easy to identify. The distinction and undoubted documental value of historic roads, together with the neglect and vulnerability of these assets, makes it essential to define specific strategies with some degree of urgency in order to appraise this heritage. In this respect, the purpose of this article is to establish a methodology with which to identify sections of historic roads that were replaced by new alignments. The decision to focus the work on these sections is based on the fact that the infrastructure of these and particularly the older sections, have undergone a smaller degree of change and subsequently retain their original routing and geometry and a far higher number and variety of heritage elements more intact. This has made it possible to ascertain the diversity of elements composing the heritage of historic roads and enables the classification of the same. The identification methodology has been applied to a significant proportion of the Spanish main road network on selecting some 15 sections of historic roads of very different characteristics. Files have been prepared for each of these sections on the basis of cartographic analysis and detailed field work, these files including data related to location, characteristics and inventory of historic elements forming the road's heritage and will subsequently include references to road layout (both longitudinal and cross-sectional), structures (essentially drainage works), auxiliary elements (signalling) and associated buildings (inns, roadworkers’ houses…). Finally, and on the basis of the experience gained during the research, an initial proposal is laid out for the heritage assessment of these assets, considering aspects such as historic, technological and documental singularity which will depend on the degree of transformation and definition of the section in question.     

The microclimate analysis of tezone ‘105’ of the Venetian Arsenale

This paper presents a detailed analysis of the measured data on the indoor air of an historical building: tezone 105 of the Arsenale in Venice. During one year of measurements, the indoor air temperature and the air humidity have been collected: the probes have been placed in different sites in order to provide total control of the microclimate. The status of the internal walls has been checked by means of the measurement of the surface temperatures by different sets of thermal resistances. The data collected point out the water wall imbibition and the high thermal capacity of the building envelope.The collected information could be used for the design of the thermal system.     

Ammonium oxalate treatment: Evaluation by μ-Raman mapping of the penetration depth in different plasters

This study is focused on the evaluation by μRaman mapping of the penetration depth achieved by ammonium oxalate treatment in different plaster specimens, a hot issue in the conservation field. The role of the carbonatic aggregate particles and the influence of the different variables of the treatment on the penetration depth and on the distribution of the newly-formed phase (whewellite) have been ascertained. Based on the results of μRaman mapping, analyses with Field Emission Scanning Electron Microscopy have been carried out in order to observe the whewellite crystals and the carbonatic aggregate particles involved in the reaction with ammonium oxalate.     

Chemical analyses of ancient glass findings excavated in the Venetian lagoon

Although Venice is regarded as being one of the most important centres of glass manufacture and trade in Western Europe, little is known about the origins of the Venetian glassmaking. Some archaeologists suggest there is a continuity in the history of glass making, in its transplantation from the Roman centres of the mainland (Altino and Aquileia), first to some islands of the lagoon, and later to the town. Some others, instead, think that there was no continuity at all and that the art of glassmaking was imported in Venice from the Islamic glass factories of the Middle East. Of great help in answering this and other technological questions is the information about the composition of ancient glass from well-dated excavations that allows to conclude on the early technology, sources of raw materials and long-distance trade. Some significant glass findings, including fragments of pots used for glass melting, were found on the island of Torcello and, more recently, in two emergency excavations in the historic centre of Venice. In this paper, the chemical composition of a large set of glass findings (and related materials) from the Venetian lagoon dating from the 7th to the 13th centuries is determined by X-ray microanalysis in order to throw new light on the glassmaking technology in the early centuries of the Venetian tradition. The results show that in this period there occurred a gradual transition from the Roman technique (a two-ingredient formulation with silica-lime sand and natron as a fluxer), towards the use of silica sand and soda plant ash. There is evidence, therefore, for a production continuity with the Roman period (melting pots and glass scraps with a natron-based composition), yet restricted to transparent blown items. No evidence was found for a local production of glass tesserae for the mosaics of the church of St. Maria Assunta in Torcello.     

Self-calibrated quantitative elemental analysis by laser-induced plasma spectroscopy: application to pigment analysis

A new laser-based spectroscopic technique, called calibration-free LIPS (laser-induced plasma spectroscopy), is proposed for fast and precise elemental analysis in the field of cultural heritage conservation and study. Quantitative stratigraphic results, obtained by CF-LIPS on ancient Roman frescoe samples, are shown. The application of this calibration-free procedure frees the LIPS technique from the need of reference samples or an internal standard. This characteristic, along with the intrinsic speed (the whole process of data collection and analysis takes a few minutes) and precision (of the order of a few parts percent) make the CF-LIPS a viable technique for in situ quantitative analysis of artworks.     

Structural investigations and analyses for the conservation of the ‘Arsenale’ of Venice

Systematic interventions are being planned and progressively designed on most buildings of the Arsenale of Venice, the Venetian republic’s shipyard, a very large complex of docks and sheds of peculiar construction characteristics. These renovation interventions are required in view of new uses for the revitalizing of that area, which is currently almost completely neglected. In the paper, after a general presentation of the main properties and of the most relevant deterioration phenomena of the principal parts of the monumental area, the methodology that is being used for the structural diagnosis, for the implementation of guidelines for the future interventions and for the maintenance of the restored conditions are presented. Some preliminary results, given by experimental tests performed both in situ and in laboratory on materials and structural elements, and by FE simulations, are discussed.     

Assessment of the state of conservation of stone artworks after laser cleaning: comparison with conventional cleaning results on a two-decade follow up

The utilization of laser light to produce fine and selective cleaning of superficial deposits and encrustation from stones was originally proposed more than 20 years ago by John Asmus who performed pioneering trials of laser cleaning on stone façades in Venice, Cremona and Padua. The opportunity to collect stone samples from these sites allowed us to carry out an original study aimed at evaluating the conservation state of stone surfaces cleaned 10–20 years ago by means of three different techniques: Nd:YAG laser radiation, micron sandblasting and chemical pads. Samples of various stone types, as Istria limestone, Botticino limestone and Nanto sandstone were collected and examined by means of optical and SEM microscopy, FT/IR, and EDAX analyses. The results provided preliminary indications that the state of conservation of stone surfaces previously subjected to laser cleaning is generally better in comparison with those which concurrently underwent mechanical and chemical cleaning.     

Past,present and future effects of climate change on a wooden inlay bookcase cabinet: A new methodology inspired by the novel European Standard EN 15757:2010

This article illustrates a preventive conservation methodology for wooden collections and objects based on the respect of the historic climate, as established by the European standard EN 15757:2010. This requires the knowledge of the past indoor climate that should be kept unchanged in the present and the future, because discontinuities would be noxious for conservation. To this aim, a very vulnerable object, i.e. a wooden inlay bookcase cabinet built by G.M. Platina in 1477 AD has been considered. The paper illustrates the methodology used to reconstruct the historic climate, i.e. with proxy data from 1500 to 1715 and from 1716 to 2009 with instrumental observations. For the present, the indoor climate of the exhibition room and the cabinet response have been investigated to remove the perturbing factors that are damaging the cabinet. For the future, the ENSEMBLES model has been used for a probabilistic forecast of the temperature and humidity over the next century, the sustainability and the potential risk for conservation connected with the expected climate change. This research constitutes an example of a novel methodology based on the relevance of the Historic climate, and includes a synergistic effort of climatologists, material scientists and conservators, to be applied for preventive conservation and to evaluate and face the negative impact of the expected climate change.