Studies on Woolen Threads from Historical Tapestries

Fourier transform (FTIR) attenuated total reflectance (ATR)and second derivative spectroscopy has been used for the first time to evaluate the state of degradation in historical woollen threads from the collections of Flemish tapestries (15th-17th centuries) in the Royal Palace, Madrid, Hampton Court Palace, and museums in Brussels. The work was performed as part of the EC-funded project ‘Monitoring of Damage in Historic Tapestries’, also known as the MODHT project. The overall aim was to develop procedures for recognising tapestries at risk and provide analysis for informing collection care. Prior to the testing of the historical threads, model tapestries were prepared according to traditional techniques of weaving and dyeing. They were then subjected to accelerated light ageing. This paper reports on the part of the MODHT project in which ATR-FTIR was used. It was selected since it is a non-destructive method, and also because it has previously been used to study the oxidation products of cystine in wool and to provide a semi-quantitative assessment of change. Evaluation was conducted on the model tapestries, and the cysteic acid peak was selected as the marker for change, as it showed a systematic change with light ageing. The same marker was usedto assess the change in historical threads

Remote Assessment of Cultural Heritage Environments with Wireless Sensor Array Networks

The logistics and cost of environmental monitoring can represent challenges for heritage managers, partly because of the sheer number of environmental parameters to consider. There is a need for a system, capable of monitoring the holistic impact of the environment on cultural materials while remaining relatively easy to use and providing remote access. This paper describes a dosimetric system based on piezoelectric quartz crystal technology. The prototype sensing module consists of an array of piezoelectric quartz crystals (PQC) coated with different metals (Fe, Cu, Ni and Sn) and includes a temperature and relative humidity sensor. The communication module involves an 802.15.4 low-power radio and a GPRS gateway which allows real time visualisation of the measurements online. An energy management protocol ensures that the system consumes very low power between measurements. The paper also describes the results and experiences from two heritage field deployments, at Apsley House in London, UK, and at the Royal Palaces of Abomey in Benin. Evaluation of PQC measurements, temperature, relative humidity and the rate of successful transmission over the communication systems are also reported

Visibilia ex invisibilibus: seeing at the nanoscale for improved preservation of parchment

This paper describes the application of atomic force microscopy (AFM) for the imaging of collagen denaturation as observed in parchment. Parchment is prepared from processed animal skin and collagen is the main component. Large collections in national archives, libraries and religious institutions contain numerous documents written on parchment. Their preservation presents an unsolved problem for conservators. The main challenge is to assess the state of collagen and to detect what conservators refer to as the pre-gelatinised state, which can cause surface cracking resulting in a loss of text and can increase the vulnerability of parchment to aqueous cleaning agents. Atomic force microscopy (AFM) was first used within the Improved Damage Assessment of Parchment (IDAP) project, enabling the characterisation of the collagen structure within parchment at the nanoscale. Damage categories were also established based on the extent of the ordered collagen structure that was observed in the AFM images. This paper describes the work following the IDAP project, where morphological changes in the fibres due to both artificial and natural ageing were observed and linked to observations made by AFM. It also explores the merits and drawbacks of different approaches used for sample preparation and the possibility of using a portable AFM for imaging directly on the surface of documents. A case study on a manuscript from the 18th century is presented

The role of organic and inorganic indoor pollutants in museum environments in the degradation of dammar varnish

This paper investigates the effects of inorganic (NO2 and O3) and volatile organic acid (acetic acid) pollutants on the degradation of dammar varnish in museum environments. Model paint varnish samples based on dammar resin were investigated by Gas Chromatography Mass Spectrometry (GC-MS), Dynamic Mechanical Analysis (DMA) and Atomic Force Microscopy (AFM). Dammar is a natural triterpenoid resin, commonly used as a paint varnish. Samples were subjected to accelerated ageing by different levels of pollutants (NO2 and O3 and acetic acid) over a range of relative humidities (RH) and then analysed. The results revealed that as the dose of the pollutant was increased, so did the degree of oxidation and cross-linking of the resin. Most interestingly, it was shown for the first time that exposure to acetic acid vapour resulted in the production of an oxidised and cross-linked resin, comparable to the resin obtained under exposure to NO2 and O3. These conclusions were supported by the analyses of model varnishes exposed for about two years in selected museum environments, where the levels of pollutants had been previously measured. Exposures were performed both within and outside the selected microclimate frames for paintings. Results showed that varnishes placed within the microclimate frames were not always better preserved than those exposed outside the frames. For some sites, the results highlighted the protective effects of the frames from outdoor generated pollutants, such as NO2 and O3. For other sites, the results showed that the microclimate frames acted as traps for the volatile organic acids emitted by the wooden components of the mc-frames, which damaged the varnish

Proof‐of‐concept study to establish an in situ method to determine the nature and depth of collagen changes in dentine using Fourier Transform Infra‐Red spectroscopy after sodium hypochlorite irrigation

AIM: To establish a method using Fourier Transform Infra-Red spectroscopy (FTIR) to characterize the nature and depth of changes in dentinal collagen following exposure to sodium hypochlorite (NaOCl) during root canal irrigation in an ex vivo model. METHODOLOGY: Fourier Transform Infra-Red spectroscopy was used to assess the changes in dentinal collagen when the root canal was exposed to NaOCl. The changes in dentinal collagen caused by NaOCl irrigation of root canals in transverse sections of roots, at 0.5 mm from the canal wall and 0.5 mm from the external root surface, were assessed by FTIR. The data were analysed using paired t-test with 5% significance level. RESULTS: Fourier Transform Infra-Red spectroscopy confirmed that NaOCl exposure caused alterations in the chemistry and structure of collagen in dentine. FTIR spectra obtained from dentine surfaces and dentine adjacent to root canals exposed to NaOCl, all consistently showed degradation and conformational change of the collagen structure. FTIR data from the ex vivo model showed that the depth of effect of NaOCl extended to at least 0.5 mm from the canal wall. CONCLUSION: In extracted human teeth, NaOCl caused changes in dentinal collagen that were measurable by FTIR. In an ex vivo model, the depth of effect into dentine extended at least 0.5 mm from the canal wall

Looking beneath Dalí's paint: non-destructive canvas analysis

A new analytical method was developed to non-destructively determine pH and degree of polymerisation (DP) of cellulose in fibres in 19th 20th century painting canvases, and to identify the fibre type: cotton, linen, hemp, ramie or jute. The method is based on NIR spectroscopy and multivariate data analysis, while for calibration and validation a reference collection of 199 historical canvas samples was used. The reference collection was analysed destructively using microscopy and chemical analytical methods. Partial least squares regression was used to build quantitative methods to determine pH and DP, and linear discriminant analysis was used to determine the fibre type. To interpret the obtained chemical information, an expert assessment panel developed a categorisation system to discriminate between canvases that may not be fit to withstand excessive mechanical stress, e.g. transportation. The limiting DP for this category was found to be 600. With the new method and categorisation system, canvases of 12 Dalí paintings from the Fundació Gala-Salvador Dalí (Figueres, Spain) were non-destructively analysed for pH, DP and fibre type, and their fitness determined, which informs conservation recommendations. The study demonstrates that collection-wide canvas condition surveys can be performed efficiently and non-destructively, which could significantly improve collection management

Controlled environment neutron radiography of moisture sorption/desorption in nanocellulose-treated cotton painting canvases

Nanocellulose-based materials have recently been used to consolidate degraded cotton painting canvases. Canvas-supported paintings consist of materials that are sensitive to moisture and especially susceptible to environmental fluctuations in temperature and relative humidity (RH). These environmental fluctuations occur in uncontrolled environments found in historic houses and palaces and can lead to hydrolytic degradation and mechanical damage to canvases. To simulate this situation in an experimental setting, canvas samples were mounted in a custom-made closed-cell and subjected to programmed cycles of RH at a controlled temperature while exposed to the neutron beam. Results are presented for both untreated samples and those treated with a polar consolidant, cellulose nanofibrils (CNF(aq)) in water, and an apolar consolidant, a composite of persilylated methyl cellulose with surface silylated cellulose nanocrystals (MC+CNC(h)) in heptane. They were then compared with changes in ionic conductivities as measured by dielectric analysis (DEA) with the same cyclic RH program and temperature. Although the samples were exposed to the same experimental conditions, they presented treatment-specific responses. CNF-treated canvas showed higher hygroscopicity than the untreated sample and facilitated moisture diffusion across the sample to areas not exposed to the environment. A sample treated with MC+CNC(h) retarded moisture diffusion during the increase in RH and could, therefore, afford protection to moisture absorption in uncontrolled environments. Thus, the experimental setup and resulting data provide a pilot study demonstrating the potential of neutron radiography in following and comparing real-time moisture diffusion dynamics in untreated and nanocellulose-consolidated cotton canvases and assisting in validating the overall benefit of the treatmen

Compromised dental cells viability following teeth-whitening exposure

This study aimed to assess the viability of dental cells following time-dependent carbamide peroxide teeth-whitening treatments using an in-vitro dentin perfusion assay model. 30 teeth were exposed to 5% or 16% CP gel (4 h daily) for 2-weeks. The enamel organic content was measured with thermogravimetry. The time-dependent viability of human dental pulp stem cells (HDPSCs) and gingival fibroblast cells (HGFCs) following either indirect exposure to 3 commercially available concentrations of CP gel using an in-vitro dentin perfusion assay or direct exposure to 5% H2O2 were investigated by evaluating change in cell morphology and by hemocytometry. The 5% and 16% CP produced a significantly lower (p < 0.001) enamel protein content (by weight) when compared to the control. The organic content in enamel varied accordingly to the CP treatment: for the 16% and 5% CP treatment groups, a variation of 4.0% and 5.4%, respectively, was observed with no significant difference. The cell viability of HDPSCs decreased exponentially over time for all groups. Within the limitation of this in-vitro study, we conclude that even low concentrations of H2O2 and CP result in a deleterious change in enamel protein content and compromise the viability of HGFCs and HDPSCs. These effects should be observed in-vivo

Violin varnishes: microstructure and nanomechanical analysis

The aim of the current work is twofold: to demonstrate the application of in situ non-invasive imaging by portable atomic force microscopy (AFM) on the surfaces of a violin and to integrate compositional and mechanical analysis at the nano scale level on model samples of varnished wood. These samples were prepared according to traditional recipes by an Italian lutemaker family well practised in the art. Samples of oil and spirit-based varnishes on maple wood, naturally and accelerated light aged, were studied. AFM was used to measure the nanomechanical properties of the model samples and established that the spirit-based varnish was stiffer than the oil-based. Synchrotron radiation micro- Fourier Transform Infra-red analysis of the layer structure revealed that stiffer spirit-based varnish showed less penetration into the wood than the oil-based. Further PeakForce Quantitative Nanomechanical Mapping (QNM) demonstrated a difference in adhesion values between the oil- and spirit-based sample