Constantina Vlachou - Mogire

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 ...

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 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.

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

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, 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.

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

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.

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.

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...

Photographic survey techniques were employed ceiling of the Queen’s Staircase at Hampton Court Pal ace mounted on an 8 metre telescopic mast, raised to ap proximately 60 cm below the ceiling images were taken from a fixed camera position method was applied with images from ten lamp positi ons map. Crosssections at the estimated surface resolution of 7.7 pixels/mm, resolution of approximately 100 microns.

Abstract The nine ceiling paintings at the Banqueting House Whitehall, painted by Peter Paul Rubens and studio is one of the largest and most complex works by the master, and has survived in its original location for almost 400 years. Historic Royal Palaces’ current Banqueting House Whitehall conservation and re-presentation project provided a rare opportunity to carry out a first-ever full and systematic technical conservation survey to determine how the paintings were created and how they have changed over the years. In 2018, scaffold access enabled the present technical survey to be conducted in-situ with a non-invasive multi-technique approach using a set of portable instruments. Notably, X-ray fluorescence (XRF) spectroscopy, integrated XRF/X-ray diffraction (XRD), optical coherence tomography (OCT) and FT-IR reflection spectroscopy were employed to study two of the paintings, the large central oval The Apotheosis of King James I (Apotheosis) and the south end rectangle The Wise Rule of King James I (Wise Rule). Results revealed information about the materials used by Rubens and his studio for the production of these large-scale paintings. Pigments identified by XRF and XRD analysis including hydrocerussite, vermillion, smalt, copper-based blue or green pigments, lead-tin yellow and iron oxide-based pigments. OCT and FT-IR analyses provided information about the nature of compounds resulting from the alteration of some original materials and the condition of varnish layers.

In 2011 Historic Royal Palaces began to investigate protective measures for historic tapestries on open display at Hampton Court Palace. The environmental exposure conditions for each tapestry were analysed and mapped to evaluate risk. An innovative method to reduce illuminance and direct sunlight on the historic tapestries using ‘smart’ technologies was developed. The design, testing and implementation of the installation of Smart Tint liquid crystal films whose optical appearance can be switched electrically from opaque to transparent, are presented. Substantial reduction (>90%) in direct light transmission could be achieved when the film is opaque. It also provides additional protection from ultraviolet (99%) and infrared radiation (98%). An entirely reversible and customised installation method had to be devised using pressure-fixed lightweight aluminium frames. An automated controller was also installed to change the individual windows from clear to opaque during different times of the day depending on their orientation and the time of the year while a dedicated wireless mesh network system enabled communication between each window and the controller. The impact of this installation is described. The use of ‘smart’ technologies offered dynamic light protection for collections on open display while maintaining the presentation of the historic room. The benefits of adopting this innovative technology include its flexible and unobtrusive installation.

ABSTRACT The political problems in Late Roman Empire caused significant changes in the coin technology. The silver content dropped severely and a new technology was introduced, which was applied in all the mints operating around the Empire. For the production of these coins, copper based quaternary alloys were used and their surface was covered by, a few microns thick, silver amalgam plating layer [1]. Hoards of these coins have been recovered in thousands from across the Empire, however, their treatment has been problematic. Both mechanical and chemical cleaning results in the damage or the complete destruction of the thin silver layer. The use of laser technology in the cleaning of works of art has a wide range of applications which includes metallic objects [2-4]. The main aim of this work was to investigate the use of lasers in the cleaning of the thin silver plating layers found in late Roman coins. Previous work showed that the case of corroded silvered copper alloy coins, required different cleaning conditions than other corroded copper coins. From the two laser wavelengths 266 and 532 nm, which were employed, the second harmonic of Nd: YAG seemed to be more controllable and promising [5]. In this paper, additional work was made to those and to other laser wavelengths, in order to minimize the chances for thermal diffusion, during the laser cleaning process, and to limit the laser absorption depth to the thin layer of corrosion near the surface. The optimisation of laser parameters was achieved through comparative cleaning tests by employing Nd:YAG (1064 nm, 532 nm and 266 nm) laser systems, using range of laser pulsing parameters on dry, wet and submerged surfaces, in order to enhance the efficiency and limit the penetration of the laser beam. The application of simultaneous microscopic monitoring during the experimental procedure helped in the successful cleaning of the coin surface. Optical monitoring was shown to be an affordable possibility for on-line control of the cleaning progress. The laser-treated surfaces were characterized using optical microscopy, scanning electron microscopy-SEM, Successful oxide removal was achieved above certain thresholds that defined the lower end of the process operating window for single-pulse operation.