Ancient materials specificities for their synchrotron examination and insights into their epistemological implications

The synchrotron characterisation of archaeological and heritage materials has undergone a steep development in the past years, among a range of other advanced characterisation techniques. For synchrotron techniques alone, close to a hundred articles were published in 2011 on such materials, prompting new developments at large scale facilities. However, few publications have discussed the speci?c characteristics of heritage materials in their advanced spectroscopic and imaging study. Here, we suggest that a greater consideration be put on the speci?cities of ancient materials and their theoretical implications on the analytical process. In particular, we discuss the importance of the a posteriori framework of the study of heterogeneous materials considered in their historicity as structuring parameters of their study. Major implications are the relevance of trace analyses, those of majors and we suggest, more importantly, the dynamics between both endpoints. The on-going development of multimodal spectral imaging appears as a way to better address corresponding difficulties. Epistemologically, we suggest that a re?exive approach be developed to explain, structure and possibly contribute to narrowing down the ?eld of possible methodological research.     

Early detection of fungal biomass on library materials

Library materials are susceptible to fungal deterioration. The paper constituents of archival materials are subjected to harmful physical and chemical processes as they are slowly consumed by fungi. Remediation of fungal contamination can be costly and risk further damage to fragile or previously degraded materials. Early detection of fungal growth would permit the use of relatively noninvasive treatments to remediate fungal contamination of artifacts before visible or lasting damage has occurred. Current methods used for the detection of microbial biomass, such as colony counts, microscopic biovolume estimation, and ergosterol analysis are expensive, time consuming, or are inappropriate for use with fungi. Beta-N-acetylhexosaminidase (EC 3.2.1.52) activity provides a rapid and reliable means of fungal detection on a variety of cultural heritage materials. Adapted for use on archival materials, fluorogenic 4-Methylumbelliferyl (MUF) labeled substrate N-acetyl-Beta-D-glucosamine (NAG) was used to detect fungal beta-N-acetylhexosaminidase activity. The fluorescence generated by minute quantities of fungi was quickly detected at an early stage of growth. The sensitivity of the assay was comparable to other biochemical techniques. The fluorometric assay was well-suited for early detection of fungal biomass on paper and assessment of the effectiveness of common remediation practices.     

A combination of NDT methods for the restoration of monumental façades: The case study of Monte di Pietà (Naples,Italy)

The paper focuses on an interdisciplinary research project concerning the preservation of the XVII century monumental building of Monte di Pietà in Naples, Italy. The building underwent a series of restorations being the structural walls affected by humidity and cracks. The importance of this monumental building in the historical city center of Naples led to design an extensive surveying program to provide the designers of strengthening with a detailed investigation of the geometry of the entire structure, and particularly of the entrance façade, with great details on several materials, thicknesses and restraints. A preliminary investigation was performed on the historical phases of this monumental building to have a clear knowledge of its vicissitudes, and then in situ structural assessment included 3D laser scanner techniques probing radar, in situ stress measures. This surveying phase was crucial especially for the subsequent Finite Elements modeling (F.E.M.) of the façade. The scope of the numerical refined analyses was to evaluate the state of stress in the structural elements of the façade putting in evidence structural ‘weak points’ and finally to design a retrofit intervention having a detailed map of the ‘intervention areas’. The theoretical damage assessment has been compared with on-site assessment and in situ stress measures. The damage primarily concerned the entrance façade and its valuable decorations. Furthermore, the basic principles for the design of the strengthening have been discussed.     

Contact sponge method: Performance of a promising tool for measuring the initial water absorption

Porous limestone and mortar are able to absorb large quantities of water. This phenomenon will accelerate the deterioration of the material. In such cases, the material might be treated with a hydrophobic product, which creates a superficial layer that hampers the penetration of water. In order to decide if such a treatment should be applied or not, the water absorbing behaviour of the material should be measured. With the same measuring technique the efficiency of the hydrophobic barrier can be evaluated. Moreover, it allows the monitoring of such barriers as a function of time. At the same time, the water absorption of porous stone material is an indication of the degree of deterioration and its sensitivity to future deterioration. Up to now, two different measuring techniques exist, but one can only be used in laboratory and the other, which can be operated in laboratory as well as in situ, is not always reliable for in situ analyses. This article proposes an alternative method: the contact sponge method. This recently developed method was tested on non-treated porous stone materials in a laboratory environment in order to evaluate its performance in comparison with the two existing methods.     

The rediscovery of Benevento Roman Theatre Acoustics

This study reports the acoustic history of the Benevento Roman theatre, from its origins in the Roman period to today. The theatre, built in the second century A.D., was abandoned following historical affairs – e.g. barbaric invasions – and natural events (earthquakes, floods, etc.). The building materials were used during the Langobardic Age for the construction of defensive walls and for the adornment of churches and buildings. During the following centuries some houses were built in the theatre. At the beginning of the 1900s, the dominating houses were demolished in order to bring to the light the buried parts of the theatre and to consolidate the structures. The recovery work ended only in 1950. The theatre is nowadays not only an ancient monument, but also the centre of important social activities with national and international festivals of music, dancing and drama. Using a software for architectural acoustic, and with a 3D theatre virtual model, we predicted the acoustic properties during the Imperial Age. With acoustic measurements carried out in situ, we evaluated the acoustic properties in the current state.     

Surveying the roofs of Rome

This study is aimed at investigating a portion of the city of Rome by means of remotely sensed Multispectral Infrared And Visible Imaging Spectrometer (MIVIS) data. A particular attention was devoted to building roofs described not only as the last defining touch given to a building, the aesthetic conclusion to a whole construction process, but also as expression and sign of a society's level of civilisation, culture and technical skill. Through the classification of objects and materials, we propose to combine history and science as different ways of interpreting a city, in this case Rome, and to implement an image processing technique as an effective tool in urban planning.     

Recording and documenting the chromatic information of architectural heritage

One essential approach in preserving architectural heritage is the documentation of 3D geometries and surface textures of historic buildings. For example, precise colour information, excluding lighting effects, is an intrinsic property of the surface materials of building interiors and exteriors. However, while colour information has been recorded for small sample areas, it has not been accurately documented on the scale of entire building surfaces. This is critical, because building materials decay and their colours fade with time. The goal of this project is to develop a method to assist in recording and documenting the chromatic information of interiors and exteriors of historic buildings with low cost and high efficiency. The method takes advantage of emerging high dynamic range imaging (HDRI) technology, which can store rich information about colour and illumination through digital photography. By recording the colour information, in addition to the geometry and texture information obtained through other existing technologies, we can achieve more complete documentation for architectural heritage. In this paper, we discuss an overview of the problem and present our algorithms for utilizing computer vision techniques to retrieve chromatic information of historic buildings. We also present and discuss our experiments and results of applying our method to studies of lab objects and the Hall of Supreme Harmony in the Forbidden City, Beijing.     

An analytical investigation of the painting technique of Italian Renaissance master Lorenzo Lotto

This paper presents the first extensive investigation of the composition of both the organic and inorganic media used by Lorenzo Lotto, one of the outstanding artists of the Italian Renaissance in the early 16th century. By investigating four paintings from The State Hermitage Museum collection (Saint-Petersburg, Russia), new insights into the artist's painting techniques were obtained, which contribute to our understanding of the transition from egg tempera to oil painting techniques that took place in Italian paintings between the 15th to the mid 16th century. Inorganic materials were determined using SEM-EDX and PLM, revealing information on the artist's palette. Of particular note was the powdered colourless glass found in the priming layer of the Madonna delle Grazie, which was most likely used as dryer. Organic materials were analysed in individual paint layers using GC-MS, and revealed a mature use of drying oils as paint binders, skilfully mixed with other organic materials and inorganic driers, to obtain the desired aesthetical and technical qualities of the paint. The study revealed that Lotto used the tempera grassa technique through most of his creative life.     

Deterioration mechanisms of building materials of Jiaohe ruins in China

Almost all defects of earthen buildings such as roughening, erosion, volume reduction, cracking as well as crazing, etc., have been witnessed in the ancient city of Jiaohe, an earthen architectural heritage in northwest China. In this paper, their long-term durability and deterioration due to prolonged exposure to environmental factors were studied, based on the basis of field investigation and laboratory analysis. The results indicated that the deterioration of building materials should be attributed to their basic properties, including density, particle size distribution, soluble salts, mineral, mechanical strength, etc., and interaction with environmental factors. And then, four main deterioration modes can be identified, namely: wind-related deterioration, water-related deterioration, temperature-related deterioration and chemical related deterioration. It can be concluded that the greatest deterioration was wind-related deterioration on west-north facing façades, and chemical related deterioration on the surface of building materials.     

Efficiently capturing large,complex cultural heritage sites with a handheld mobile 3D laser mapping system

Accurate three-dimensional representations of cultural heritage sites are highly valuable for scientific study, conservation, and educational purposes. In addition to their use for archival purposes, 3D models enable efficient and precise measurement of relevant natural and architectural features. Many cultural heritage sites are large and complex, consisting of multiple structures spatially distributed over tens of thousands of square metres. The process of effectively digitising such geometrically complex locations requires measurements to be acquired from a variety of viewpoints. While several technologies exist for capturing the 3D structure of objects and environments, none are ideally suited to complex, large-scale sites, mainly due to their limited coverage or acquisition efficiency. We explore the use of a recently developed handheld mobile mapping system called Zebedee in cultural heritage applications. The Zebedee system is capable of efficiently mapping an environment in three dimensions by continually acquiring data as an operator holding the device traverses through the site. The system was deployed at the former Peel Island Lazaret, a culturally significant site in Queensland, Australia, consisting of dozens of buildings of various sizes spread across an area of approximately 400 × 250 m. With the Zebedee system, the site was scanned in half a day, and a detailed 3D point cloud model (with over 520 million points) was generated from the 3.6 hours of acquired data in 2.6 hours. We present results demonstrating that Zebedee was able to accurately capture both site context and building detail comparable in accuracy to manual measurement techniques, and at a greatly increased level of efficiency and scope. The scan allowed us to record derelict buildings that previously could not be measured because of the scale and complexity of the site. The resulting 3D model captures both interior and exterior features of buildings, including structure, materials, and the contents of rooms.     

Diagnosis of weathered Coptic wall paintings in the Wadi El Natrun region,Egypt

This paper deals with the impact of soluble salts on the deterioration of wall paintings in the region of Wadi El Natrun in Egypt, including the identification of the building materials and pigments used. For this purpose we used XRD analysis which proved that the green pigment in the Church of the Virgin, Wadi El Natrun is a mix of malachite and hydrocerussite, and the black pigment is graphite. The results proved that the building materials (stones, mortar, and plaster) in Wadi El Natrun are affected by ground water as they have the same soluble salts at different concentrations. The Wadi El Natrun lakes are the native source of natron salt, which has been used in mummification techniques. Soda lakes represent the major types of naturally occurring highly alkaline environments. The factors leading to the formation of the alkaline saline deposits may be divided into climatic, geological, and topographical. Climatic and topographical factors control the amount of water entering the system as rainfall or surface runoff and the amount leaving by evaporation. Geochemical factors determine which ions enter the system. Solutions of carbon dioxide result in the formation of a weak carbonic acid, which dissolutes the mineral components of the surrounding rocks and archaeological buildings, leading to their ion release.     

Laser scanning and digital imaging for the investigation of an ancient building: Palazzo d’Accursio study case (Bologna,Italy)

This paper describes a scientific approach aimed at studying the ancient part of Palazzo d’Accursio (Bologna, Italy), a masonry building which is part of the Italian cultural heritage. Laser scanning and the inspection of digital images are used to detect traces of restoration works and other interesting features related to both architectural marks and natural or anthropic events. One of the main elements of the method is the analysis of residual maps, obtained by computing the differences between the point coordinates of the façade and reference fit planes. The obtained results, based on both radiometric and geometrical analysis, are used to provide a reasonable hypothesis as to the original configuration of the studied building, while taking into account the available historical information about the constructive phases of the building.     

Pigment identification in a Greek icon by optical microscopy and infrared microspectroscopy

Optical microscopy, cross-section and fragment Micro-FTIR spectroscopic techniques along with microchemical tests were used for the identification of pigments in two different samples of an icon. Representing the Last Judgement, and painted by the Greek master Ioannis from the village of Kapesovo in the year 1771, the kneeling desk icon under investigation is a noteworthy contribution to the study of materials in post-Byzantine visual arts. The main components found in the ground layer of both samples were gypsum, beeswax and a proteinaceous material. Cinnabar, Prussian blue and cerussite were identified on the paint layers. The binding medium on the paint layers was weddelite. The materials used in the painting and ground layers were characterized in order to clarify the painting technique. Proteinaceous materials have been identified as binders for the pigments, indicating a tempera painting technique.     

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.     

Analysis of efflorescence on surface of beeswax seals

Thirteen samples of an efflorescence collected from the surface of beeswax seals or from beeswax used for their restoration were analysed in detail. The samples were of different origin, age and storage history. The composition and the incidence of the efflorescence was correlated with a chemical composition of historical and recent beeswax samples. The composition of the crystalline layer was found to be very similar in all the samples. Linear monounsaturated alkenes containing 31 and 33 carbon atoms, more precisely (Z)-hentriacont-10-ene and (Z)-tritriacont-10-ene, were identified as main components. The analyses of beeswax have revealed that all compounds identified in “wax bloom” naturally occur in recent beeswax. However, the historical beeswaxes contained only traces of unsaturated hydrocarbons, if anything. The efflorescence was observed primarily on the surfaces of those samples which contained larger proportion of alkenes. The presented results could be of particular importance not only for better understanding of the described phenomenon, but also for the development of new beeswax-based materials, which would be “bloom resistant” and useful for conservation purposes.     

Teodelinda's tales at Monza Cathedral: A physico-chemical diagnosis of the pictorial cycle

The pictorial cycle “Teodelinda's Tales” at Monza Cathedral, painted by Zavattari and his sons in 1444–1446, has been investigated by optical and SEM-EDS microscopy and microFT-IR spectroscopy. Paint layers, gildings and other metallic decorations have been analysed to elucidate the execution technique, the state of conservation and the possible retouchings in consequence of deterioration processes. Organic binders, coatings and adhesives have been also identified especially by microFT-IR spectroscopy applied directly to the sampled powders or fragments and to their solvent–soluble fractions. The obtained data offer a correct and satisfactory knowledge of the original organic and inorganic materials and those used in the subsequent retouches and restorations, their state of conservation and the painting techniques (fresco, mezzo fresco and secco).The physico-chemical investigations allowed to identify the nature and sometimes the provenance of the employed materials (i.e. ultramarine blue pigments) and some decay markers, particularly useful in understanding and describing the cycle realised by the authors and the modifications suffered along the centuries, and also to propose an integrated methodology for the scientific study of the mural paintings.     

Initial results on laser cleaning at the Victoria & Albert Museum,Natural History Museum and Tate Gallery

A collaborative project between the Materials Department of Imperial College, the Victoria & Albert Museum, Natural History Museum and the Tate Gallery was initiated with the objective of introducing laser cleaning in these London-based museums and establishing a long-term research collaboration. An access to these material conservation departments means that materials like traditional statuary materials, heavily corroded metals, ivory, palaeontological samples, textiles, stained glass, plaster and some modern materials can be used to investigate the usefulness of laser cleaning and study their effects using a wide range of analytical techniques.     

A portable NMR device for the evaluation of water presence in building materials

The direct recording of the water presence in stone materials or in masonry provides information about their state of conservation and it can also indirectly reveal the effectiveness and durability of protection treatments or chemical interventions for rising damp reduction. Evaluating the humidity, i.e. the water content, of a building material is a problematic issue because the water is distributed in a large volume in different amounts. Usually these kinds of measures have been carried out with resistance/conductivity and thermographic systems, which are all affected by weaknesses and intrinsic restrictions. Thermographic investigations are affected by temperature differences and the evaporation–cooling effect. In the case of electric measures, the signal does not originate from the water present, but from the conductivity of the water itself, which is strictly connected to the presence of ion species that can modify it significantly. Moreover, interruptions, like air gaps or fractures, cancel the signal. For both methodologies the quantitative water evaluation is difficult. Although some minerals, like iron-based ones, could disturb the NMR measure, the signal is not influenced by the presence of most common soluble salts or pollutants in the solution (such as nitrates, chlorides or sulphates) and it is only generated by the number of water molecules present in the sensitive volume. In this paper the results, obtained in the laboratory with a portable NMR device, developed within the framework of the Eureka Project E!2214-MOUSE, are shown. The encouraging results obtained in this preliminary experiment, concern mainly the investigation of stone materials that have different porosimetric features and the calibration of the instrument under different working conditions. The experiments focused on the correlation between the content of water absorbed by capillarity and the NMR signal intensity obtained by this device. Different materials have been investigated, such as calcarenite and bricks. The experimental work will define a starting platform to successfully transfer the analytical procedure from the laboratory to in situ measurements.     

Study on some sorption properties of treated bentonites for their potential use as a moisture regulating system for the preservation of historical wooden elements

We report the first results of a research study aimed at developing a new strategy for the conservation of wooden structural elements present in historical buildings, based on moisture regulating systems. As has been happening for artefact preservation in museums, the idea is to develop systems based on the ability of some highly hygroscopic materials to moderate variations in relative humidity. These materials could adsorb and release moisture to reduce the extreme values of humidity in the micro-climate, for example between wooden beams and masonry. In order to experimentally verify this possibility using current, low cost and easy handling building materials, 5 bentonite samples were laboratory processed to improve their adsorbing properties by means of treatment with sodium carbonate at 3 concentrations: 2, 3 and 4% by weight. The effectiveness of ion exchange between sodium carbonate and bentonite was controlled by measuring the swelling volume of the bentonites. All the samples (n = 15) were tested for their hygroscopic properties. Adsorption isotherms were measured at 25 °C, using desiccators with silica gel, saturated salt solutions and bi-distilled water. A comparison between isotherms of one of the lower hygroscopic treated sample of bentonite and of a sample of wood and of a sample of brick and some numerical analyses with the Delphin code were made in order to evaluate the potential use of this bentonite as a moisture regulating system for the preservation of historical wooden elements. Results show that it seems to be possible to use bentonites as a moisture buffering material in order to reduce moisture content in wooden beams at least during their adsorption phase. It remains to investigate their desorption phase and their behaviour if they be in a saturation condition. Further studies are currently under way.     

The Basilica of San Vitale in Ravenna: Investigation on the current structural faults and their mid-term evolution

A finite element model was developed to analyze the Basilica of San Vitale in Ravenna (Italy), a Byzantine building which suffers diffused cracking and excessive deformation, mainly as a consequence of complex architectural vicissitudes (extensions, demolitions …) and ground settlements. In the structural analyses, account was taken of permanent loads (self-weight), boundary displacements increasing in time, and seasonal thermal changes. Thanks to previous topographical surveys of part of the building, to chemical and mechanical investigations, the geometry of the Basilica and the main physical properties of the materials are reasonably well defined. The geometric model does not virtually neglect any structural element and accounts for the lack of symmetries in the building. Because of the complexity of the geometric model, a simplified (linearly elastic, isotropic) constitutive law had to be assumed to keep the computing time within reasonable limits. Accordingly, the performed analyses constitute only a first step toward the understanding of the structural behavior of the Basilica, as the adopted constitutive law can only partially explain the surveyed crack pattern, which is influenced by the brittleness and the anisotropy of the constituent materials.