Papers by Constantina Vlachou - Mogire
Metallography, Microstructure, and Analysis
Heritage
Hyperspectral imaging has emerged as a promising analytical method of artwork due to its potentia... more Hyperspectral imaging has emerged as a promising analytical method of artwork due to its potential in combining non-invasive analytical capabilities and imaging allowing the survey of the entire (or of a large area of the) surface of an artwork, which is a highly significant application for historic tapestries. This project deployed a high-resolution ClydeHSI Art Scanner, which was used with both a push-broom visible to very-near infrared (VNIR; 400–1000 nm) and near infrared (NIR; 900–1700 nm) hyperspectral cameras. Initial testing focused on the characterisation and mapping of the different materials used on historic tapestries (wool, silk, metal threads). To facilitate the dye characterisation, a collection of wool and silk samples dyed with recipes based on medieval practices was used. The samples measured using the system and the data collected formed an external reference library including the type of the natural dyes and mordants used during their production. The outcomes of ...
Presented at: 1st International Conference on Science and Engineering in Arts, Heritage and Archaeology (SEAHA), London, UK. (2015), Jul 15, 2015
Particulate matter can cause a loss of value of in indoor heritage, and for this reason it is fre... more Particulate matter can cause a loss of value of in indoor heritage, and for this reason it is frequently monitored. The process of deposition is well-described by theoretical models that relate deposition rates with environmental variables. However, we find that the inputs and outputs of models are not directly relevant to preventive conservation. While heritage managers are concerned about area coverage by particulates, the existing models use deposition velocities as the main variable. We propose an improved graphical representation of predictions of deposition, that takes inputs that can be modified as part of preventive conservation plans (concentration and air movement) and an output that can be related to risk assessment and cleaning schedules (time to visible area coverage). By comparing the predictions with experimental data, we show that this approach is useful for small particles of outdoor origin. We also find that further research is needed to make numerical predictions ...
ABSTRACT Laser cleaning tests were performed on ancient (Roman and Byzantine) coins, which belong... more ABSTRACT Laser cleaning tests were performed on ancient (Roman and Byzantine) coins, which belong to the collection of the Numismatic Museum of Athens, Greece. Coins with various types of surface corrosion were studied, using Q-switched Nd:YAG, CO2 and Er:YAG lasers and a range of laser pulsing parameters on dry and wet surfaces. A section of each object was cleaned mechanically, by the conservators of the museum in order to show the results of this method. It was discovered that the results of laser cleaning was influenced by the type of corrosion of the surface of the coins. X-ray fluorescence was applied as analytical technique. The results show that XRF could provide detail information about the surface chemical nature of the treated objects, as well as about their past and present state and it leaded to recommendations for restoration with the appropriate laser cleaning conditions.
Proceedings of SPIE - The International Society for Optical Engineering, 2009
This work investigates the influence of the pulse duration and the wavelength on the laser cleani... more This work investigates the influence of the pulse duration and the wavelength on the laser cleaning of thin silver plating layers found in late Roman coins. Comparative cleaning tests were performed using Nd:YAG (1064 nm and 532 nm - 6 ns), GaAlAs diode (780 nm - 90 ps) and Ti-Sapphire regenerative amplifier (800 nm - 100 fs) laser systems. The
IOP Conference Series: Materials Science and Engineering, 2018
Historic tapestries are very important and complex artworks. Their heterogeneous structure compos... more Historic tapestries are very important and complex artworks. Their heterogeneous structure composed with different materials is weaved in warp and weft threads with the objective of render an image to be displayed. Often on open display these objects are exposed to forces caused by their own weight as well as by the strain experience due to moisture adsorption and desorption cycles when temperature and relative humidity of the surrounding environment fluctuate. Since physical damage is usually supported by conservation stitching techniques there is a need to understand how certain decisions would influence future mechanical behaviour of a tapestry. This requires the need of establishing a methodology that helps to understand how different sections of these heterogeneous objects respond when forces are applied to them. Past research considered tensile testing of primarily new woven aged sections which are not representative of the historic tapestries [1]. Digital image correlation (DIC) was also successfully used in order to characterize the strain states of woven tapestries [2]. However, information on how wool and silk behaves as well as the influence of damage and stitching in some areas is still scarce and there is the lack of a methodology for a full strain analysis. In this research, tensile mechanical behaviour is being studied in order to inform on how different fragments of historic tapestries behave when a certain tensile force is applied on them. For this, a new methodology of analysis is proposed. Force strain curves collected from tensile tests are analysed together with complementary DIC data to understand the strain states that were present in different stages of the mechanical tests. Results proved that a holistic methodology, using both techniques required for successful interpretation of data. Furthermore, this experimental work demonstrated that tapestry areas behave differently when a tensile force is applied.
Reigate stone was extensively used in medieval London and is prone to rapid decay. A variety of d... more Reigate stone was extensively used in medieval London and is prone to rapid decay. A variety of different conservation treatments has been applied in the past; in many cases, these have not mitigated on-going decay. This paper presents an overview of wax, limewash, silane and ammonium tartrate treatment at the Tower of London and Hampton Court Palace. Documentary analysis and visual inspection indicate that whilst these methods have provided protection to some stones, no single method has resulted in the protection of all stones. Non-destructive and minimally-destructive testing is used to more closely assess the effects of ammonium tartrate treatment. The results imply that inherent stone mineralogy, past decay pathways and/or present environmental factors are a greater influence on ongoing decay than treatment histories. ARTICLE HISTORY Received June 2019 Accepted March 2020
Reigate Stone was used extensively in South-East England between the 11th and 16th Centuries, con... more Reigate Stone was used extensively in South-East England between the 11th and 16th Centuries, contributing to a legacy of medieval heritage that ranges from parish churches to royal palaces. It is a glauconitic malmstone, a unique building stone to the British Isles. It was easy to carve decoratively, however also highly susceptible to degradation. By the 15th Century many buildings were already in an advanced stage of decay. Long subject to wide-scale replacement, attempts at conserving what little remains have increased in accordance with modern practice. The Tower of London has been a testing ground for a range of methods, yet the causes of decay remain poorly understood. The MRes project will employ a field-based methodology; learning from the current condition of Reigate Stone in situ, informed by knowledge of both their history (previous treatments and environmental data) and their current local environment. This will focus on the Tower of London, given its relatively large stock of Reigate and the long history of conservation efforts. Research will be supported by investigations at Hampton Court Palace, to assess the influence of local climate (e.g. pollution). A range of environmental monitoring and non-destructive testing methods will be employed. Following an initial stock take, a more detailed survey will be conducted on noticeable typologies. These should inform a database of situations and conditions. This stage of the project will cover the anamnesis and initial diagnosis of Reigate Stone decay, by providing a full condition survey of two key sites. This data will assist laboratory testing, to be conducted during the DPhil. The overall aim will be to develop a system dynamics approach, by linking degradation to measurable parameters.
Studies in Conservation, 2020
Studies in Conservation, 2020
In article problems of network interaction between the educational organizations, and also exampl... more In article problems of network interaction between the educational organizations, and also examples of their decision, on the example of URTK of A.S. Popov are considered.
Studies in Conservation, 2020
Banqueting House, completed in 1622, is the only surviving building of London’s royal palace of W... more Banqueting House, completed in 1622, is the only surviving building of London’s royal palace of Whitehall. Suspended within the ceiling of the Banqueting House since 1636 is a unique in situ ceiling painting series by Sir Peter Paul Rubens (Figure 1). As part of an on-going programme to conserve and re-present the Banqueting House, the building’s exterior was conserved in 2016 and a series of due diligence studies have been undertaken to develop a position for the conservation of the interior including its ceiling paintings, within the context of a conservation-regulated Grade 1 listed site. Given their significance, the paintings warrant an approach to their comprehensive care that is of the highest quality achievable by today’s advanced conservation standards and will last for decades to come. A project of this immense scale (with a total canvas area of 247 m) required a team of conservators, building surveyors and scientists at Historic Royal Palaces (the independent U.K. charity that looks after the Banqueting House and funds this major project) to take an evidence-based decision-making approach, working within this ‘whole building’ heritage conservation project. An iterative, phased decision-making process for the planning of the major project has been directed by due diligence studies comprising technical conservation research, scientific investigation and debate, to arrive at an informed proposal for the conservation and presentation of such an important interior scheme within the wider setting of a heritage site. Due diligence is a business-focused decision-making approach to a conservation project whereby many aspects of research are carried out to provide stakeholders with multiple options and ranges of how far to proceed with the full implications of each option so that they can be evaluated to decide the overall approach. This project has provided a rare opportunity to carry out a full systematic technical conservation survey of all nine paintings, utilising a range of scientific methods and archival research to determine how the paintings were created, how they have changed and establish an accurate record of their condition (Figure 2). Since installation in 1636, nine restorations have occurred: most significantly, in 1906–1907, the paintings were given a rigid pasted-on lining with a plywood board ‘marouflage’ backing that remains to this day, well adhered. Accounts indicate the paintings have been removed from the ceiling five times, the most dramatic occurring during the Second World War when the larger five paintings were cut up to move all nine to safe storage outside London. In addition to condition, the project also considered the legibility of the paintings. Discoloured past restorations, multiple varnish layers, blanching, accretions, and crust formation affect portions of the surface and, with limited access to the paintings at a ceiling height of 17 m, previous restorations have only been able to remove these defects partially. A due diligence approach, for such a significant artwork and heritage site, has required the concurrent delivery of investigations that increase the quality and amount of relevant technical information accessible to us as decision-makers, ensuring that systematic research drives the planning process for an ultimate conservation campaign by clarifying and prioritising the benefits and risks involved. Through a number of studies to date from 2016 to 2018, and with a wide range of internal and external experts (including an expert advisory group), conservators assessed the feasibility and benefits of a number of conservation treatment options. Three strands of technical research delivered a step change in understanding of the materials, condition and treatment options for the ceiling painting, its structural elements and surround; the environment within the building, including computational fluid dynamics modelling to propose the most effective building and services adaptations to improve preservation conditions; and consideration of appropriate presentation standards for a painting scheme by Rubens. The research has involved the
Studies in Conservation, 2020
ABSTRACT Vibration generated by use of masonry equipment can be a threat to wall paintings. Its a... more ABSTRACT Vibration generated by use of masonry equipment can be a threat to wall paintings. Its assessment, mitigation and control is of critical importance to risk management and the safeguarding of works of art, particularly those which are immovable. The planned programme of window restoration in the Royal Gallery, Palace of Westminster, started in 2016, directly above the monumental wall painting of Trafalgar, had the potential to cause serious damage to this painting. For a period of 18 months the Curator’s Office worked with stakeholders, conservation scientists, conservators and stone masons to minimise risk. The project developed a monitoring strategy, set vibration thresholds, managed risk and negotiated the use of tools and working methods. To assess vibration data loggers equipped with 3-axis acceleration sensors were installed at critical locations. To corroborate these findings assessment was undertaken using a sound level analyser. This assessed acceleration at a series of frequencies in the 0–100 Hz range considered most damaging to artworks. However, a critical component was conservator-led in situ monitoring of vibration. When necessary, this live monitoring allowed conservators to dynamically assess and negotiate the adaptation of tools and techniques to reduce levels. This real-time approach proved essential in understanding peaks and changes in levels of vibration; informing discussion between stakeholders, ensuring monitoring translated into effective preservation.
Studies in Conservation, 2018
W pracy przedstawiono wyniki badań przyczyn pękania ścian szczelnych kotłów gazowych podczas eksp... more W pracy przedstawiono wyniki badań przyczyn pękania ścian szczelnych kotłów gazowych podczas eksploatacji. Zakres badań obejmował badania metalograficzne oraz badania twardości. Ujawnione struktury pozwoliły w jednoznaczny sposób określić przyczynę uszkodzenia ścian szczelnych spawanych hybrydowo. Stwierdzono, że przyczyną pękania była korozja naprężeniowa, spowodowana równoczesnym oddziałaniem statycznych naprężeń rozciągających i środowiska korozyjnego.
Additional file 2. Scatter plot results from permutation tests carried out on the measured oxidat... more Additional file 2. Scatter plot results from permutation tests carried out on the measured oxidation ratios: cysteic acid/cystine dioxide (CA/CD), cysteic acid/cystine monoxide (CA/CM) and cystine dioxide/cystine monoxide (CD/CM).
Additional file 1. Principal component analysis score and loading plots of the first 5 principal ... more Additional file 1. Principal component analysis score and loading plots of the first 5 principal components from NIR data of undyed unaged wool, undyed light aged wool (600 h, 150,000 lx) and historic fragment wool yarns. Outlier points have been highlighted in red.
A preprint of the article submitted to Studies in Conservation on November 30, 2018 as a contribu... more A preprint of the article submitted to Studies in Conservation on November 30, 2018 as a contribution to LACONA 12 conference special issue.
Minerals
The correct choice of pointing mortar is considered crucial to the conservation of historic mason... more The correct choice of pointing mortar is considered crucial to the conservation of historic masonry. A proliferation of cement and eminently hydraulic lime mortars since the late 19th century has accelerated the deterioration of built cultural heritage in many parts of the world. Whilst the use of softer, lime-based mortars in stone conservation is now common practice, their role in the overall conservation strategy of highly vulnerable building stones such as Reigate Stone requires assessment. In this paper non-destructive testing (NDT) is used across a two-year period to investigate the impact of different pointing mortar types in situ. NDT data on surface hardness and moisture are interpreted at different scales to assess moisture regulation of Reigate Stone masonry at the Wardrobe Tower, a ruined structure at the Tower of London, following repointing carried out in Spring 2017. Joints repointed using a hydraulic lime mortar (NHL3.5) are shown to regulate moisture in adjacent Rei...
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Papers by Constantina Vlachou - Mogire