Article

Analysis and diagnosis of the state of conservation and restoration of paper-based artifacts: A non-invasive approach

Authors:
If you want to read the PDF, try requesting it from the authors.

Abstract

We report a non-invasive and multi-analytical physico-chemical method for the characterization of paper artworks, able to identify sizing, inks, and glues and to quantify oxidative degradation by-products. The proposed methodology is mostly carried out in situ by using easy-to-use and cheap portable instrumentation for the acquisition of multispectral images, punctual ultraviolet-visible-near infrared fiber-optics reflectance spectroscopy (FORS) and punctual fiber optics fluorescence spectroscopy. Further analytical information is provided by non-invasive in-situ sampling of paper surface by using soft latex sponges, making possible laboratory chromatographic and infrared spectroscopic analyses on the aqueous sponge extracts. The proposed diagnostics method was applied to two 17th century letters written by St Francis of Sales (1567–1622), collected at the Chigi Palace in the town of Ariccia (Italy). Results show an intense oxidative degradation of the letters, also localized in water spots, and the presence of carboxylic acids by-products. Analysis of FORS spectra provided the concentration of chromophores in the paper substrate. The diagnostic method allowed the identification of gelatin sizing, the presence of starch glue in specific areas of the letters and the type of ink used in the text. Our diagnostic approach aims to offer to conservator-restorer a characterization of a paper artwork, that can be applied to other, for a correct planning of conservation interventions.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

ResearchGate has not been able to resolve any citations for this publication.
Article
Full-text available
In this work, we shed new light on ultrasound contrast agents applied to the field of cultural heritage as an invaluable fine-tune cleaning tool for paper artworks. In this context, one of the primary and challenging issues is the removal of modern adhesives from paper artifacts. Modern adhesives are synthetic polymers whose presence enhances paper degradation and worsens its optical features. A thorough analytical and high-spatial-resolution combined study was successfully performed to test the capability of poly(vinyl alcohol)-based microbubbles stimulated by a proper noninvasive 1 MHz ultrasound field exposure in removing these adhesives from paper surfaces, in the absence of volatile invasive and toxic chemicals and without damaging paper and/or leaving residues. We demonstrate that poly(vinyl alcohol)-shelled microbubbles are suitable for interacting with paper surfaces, targeting and boosting in a few minutes the nondamaging removal of adhesive particles from paper samples thanks to their peculiar shell composition together with their ultrasound dynamics.
Article
Full-text available
Digital images represent the primary tool for diagnostics and documentation of the state of preservation of artifacts. Today the interpretive filters that allow one to characterize information and communicate it are extremely subjective. Our research goal is to study a quantitative analysis methodology to facilitate and semi-automate the recognition and polygonization of areas corresponding to the characteristics searched. To this end, several algorithms have been tested that allow for separating the characteristics and creating binary masks to be statistically analyzed and polygonized. Since our methodology aims to offer a conservator-restorer model to obtain useful graphic documentation in a short time that is usable for design and statistical purposes, this process has been implemented in a single Geographic Information Systems (GIS) application.
Article
Full-text available
Herein, colloidal dispersions of alkaline nano-particles (NPs: CaCO 3 and Mg(OH) 2) are stabilized by trimethylsilyl cellulose (TMSC) in hexamethyldisiloxane and employed to treat historical wood pulp paper by an effortless dip-coating technique. Both alkaline NPs exhibit high stability and no size and shape changes upon stabilization with the polymer, as shown by UV−vis spectroscopy and transmission electron microscopy. The long-term effect of NP/TMSC coatings is investigated in detail using accelerated aging. The results from the pH-test and back-titration of coated papers show a complete acid neutralization (pH ∼ 7.4) and introduction of adequate alkaline reserve even after prolonged accelerated aging. Scanning electron microscopy−energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and infrared and water contact angle measurements showed the introduction of a thin and smooth hydrophobic NP/TMSC coating on the paper fibers. Acid-catalyzed desilylation of TMSC was observed by declining C-Si infrared absorbance peaks upon aging. The CaCO 3 coatings are superior to Mg(OH) 2 with respect to a reduced yellowing and lower cellulose degradation upon aging as shown by colorimetric measurements and degree of polymerization analysis. The tensile strength and folding endurance of coated and aged papers are improved to 200−300 and 50−70% as illustrated by tensile strength and double folding endurance measurements.
Article
Full-text available
A new approach to the conservation of paper manuscripts is proposed that leads to both deacidification and strengthening of paper. The study was carried out by using polyamidoamines (PAAOHs) functionalized with alcoholic groups, in their native form (PAAb) or neutralized with boric acid (PAAn). They were applied on model paper samples containing iron-gall ink spots through agar rigid gel or by brushing. Preliminary evaluation of the effects of polymer concentration, methods, and duration of application have been tested on model ink-free paper samples. The improvements induced by PAAOHs on paper samples was revealed by surface pH (evaluated in ink-free areas, inside ink spots and on the edges between them) and by measurements of alkaline reserve according to TAPPI T 553 pm-92. The results showed the different behaviour of ink-free and inked regions due to high acidity of iron gall ink. In fact, although a treatment with solutions having low concentration (i.e. 0.1 and 0.15 M) is sufficient for preserving ink-free paper samples from ageing, higher concentration of polymer (0.3 M) or extra brushing application are needed in order to get a complete deacidification of the ink spots. As a side-effect of deacidification treatments, PAAOHs promoted a significant reduction of thermo-hygrometric ageing effects and water smearing at the edge of iron-gall ink spots, as suggested by Raman spectroscopy and mechanical analyses. Graphical abstract Open image in new window
Article
Full-text available
This study presents mid and near-infrared (7500-375 cm ⁻¹ ) total reflection mode spectra of several natural organic materials used in artworks as binding media, consolidants, adhesives, or protective coatings. A novel approach to describe and interpret reflectance bands as well as calculated absorbance after Kramers-Kronig transformation (KKT) is proposed. Transflection mode spectra have represented a valuable support both to study the distorted reflectance bands and to validate the applicability and usefulness of the KK correction. The aim of this paper is to make available to scientists and conservators a comprehensive infrared reflection spectral database, together with its detailed interpretation, as a tool for the noninvasive identification of proteins, lipids, polysaccharides, and resins by means of portable noncontact FTIR spectrometers.
Article
Full-text available
Cellulose oxidative and hydrolytical degradation is one of the greatest problems for the conservation of paper supports. To contrast these degradation processes, both deacidification and reduction of the oxidized functions are needed. Dealing with original documents, it is often impossible to perform the two mentioned treatments in aqueous solutions and in a distinct subsequent way, because of the fragility of the artifacts. After studying, in a separate way, an effective deacidifier (calcium propionate) soluble in ethyl alcohol and many reducers (boron complexes), able to act in different non-aqueous solvents, it was decided to test a simultaneous method of deacidification and reduction in ethanol. This paper presents the chemical-physical results obtained by applying simple deacidification and simultaneous deacidification-reduction on laboratory paper samples that were artificially aged and then re-measured after 10 and 15 years of natural aging. Results show that all alcoholic treatments are very effective: papers are stable also after a long period of both artificial and natural aging.
Article
Full-text available
This research deals with the use of water soluble polyamidoamines (PAAOH’s) as innovative paper preservatives endowed with deacidification and biostatic properties. They were obtained by reaction of N,N-methylenbisacrylamide (MBA) with ethanolamine (EA) and were characterized by Fourier Transform Infrared Spectroscopy analysis (FTIR), Electrospray Mass Spectrometry (ESI-MS) and Nuclear Magnetic Resonance (NMR). PAAOH’s should tightly bind to cellulose through a network of H-bonds, as suggested by molecular mechanics calculations. Actually, FTIR analysis and the increment in anhydrous mass of paper samples demonstrated that PAAOH’s were progressively absorbed by paper cellulose without altering the original color of paper as observed by colorimetric analysis. The deacidifying effects were confirmed by significant increment in pH values of paper after treatment in comparison to the untreated paper samples. In vitro antibiogram assay showed a good but variable biostatic effect on different fungal test strains, depending by species, PAAOH’s concentration and pH in the substrate.
Article
Full-text available
Wet cleaning of ancient papers is one of the most delicate and important steps in a restoration process. It allows to improve the optical quality of a graphic work as the removal of pollution and of organic substances resulting from cellulose degradation. Nevertheless, washing by immersion – the traditional process – usually involves a substantial impact on the original morphological structure of paper and could be dangerous for water sensitive inks and pigments. Furthermore it is very important that the time of the cleaning process is optimized in order to remove all contaminants, thus minimizing invasive treatments and time costs.
Article
Full-text available
Wet cleaning of ancient papers is a common treatment performed for the removal of degradation products, external contaminants and salts, which can promote the degradation of cellulose (i.e., hydrolysis, oxidation). In this research, the effects on the mechanical properties of paper samples caused by wet cleaning treatments were evaluated by considering the changes induced in the ultimate tensile strength, deformation at break and flexibility. For this purpose, samples were subjected to different aqueous cleaning treatments such as immersion in deionised water and the application of rigid gels of agar and gellan gum at different concentrations was carried out. Tensile tests were run, and morphological observations of paper by means of light microscopy and scanning electron microscopy were recorded. Contrary to the significant changes in the mechanical properties of paper samples after immersion treatment (an increase in flexibility as the elongation at break), the use of gelled systems caused slight improvement in the mechanical properties of paper (in both the ultimate tensile strength as well as in the breaking strain). Changes in the mechanical properties of paper were also correlated with slight changes in the diameter of the cellulose fibres as a consequence of the swelling action of water molecules, especially in the case of immersion treatment. Finally, the tensile tests performed on the paper samples after thermo-hygrometric accelerated artificial ageing (70 °C and 65 % RH) demonstrated that cleaning treatments by rigid gels did not seem to accelerate any sort of paper degradation in the mid to long term.
Conference Paper
Full-text available
In a joint research project with the Ulm University Medical Center, the Ulm University of Applied Sciences is developing a bioreactor for tissue engineering of facial cartilage. The cartilage growth will be monitored by a spectral camera to obtain cartilage composition and thereby to ensure cartilage quality. By excitation the cartilage with UV light, it is possible to record low intensity fluorescence spectra in the spectral range from 380 to 500 nm over the surface of a cartilage specimen. At present the camera records fluorescence spectra along a line of several hundred points. Further developments will allow obtaining fluorescence spectra in two dimensions by a single snapshot.
Article
Full-text available
Alkaline earth metal hydroxide nanoparticles dispersions have demonstrated to be efficient for the preservation of cellulose-based artifacts, providing a stable neutral environment and, if in excess, turning into mild alkaline species. New formulations tailored for specific conservation issues have been recently obtained via a solvothermal reaction, starting from bulk metal, and short chain alcohols. Using this synthetic procedure, stable, and high concentrated calcium hydroxide nanoparticles dispersions can be obtained. The characterization of nanoparticles was carried out by dynamic light scattering, transmission electron microscopy and X-ray powder diffraction and showed that the dispersed systems are particularly suitable for the application on porous substrates. In a direct application of this technology, acidic paper and canvas samples were artificially aged after deacidification using calcium hydroxide nanoparticles dispersed in short chain alcohols. Cellulose viscosimetric polymerization degree (DPv), cellulose pyrolysis temperature, and samples' pH were evaluated upon the aging and in terms of protective action arising from the applied treatment. In particular, determinations of DPv clearly showed that the degradation of acidic paper and canvas samples proceeds at higher rates with respect to deacidified samples. These evidences were also confirmed by the thermogravimetric analysis of samples, in which the benefits due to the deacidification treatments are measured in terms of pyrolysis temperature of cellulose. These new formulations of nanoparticles dispersions expand the palette of available tools for the conservation of cellulose-based works of art, such as easel paintings, and manuscripts, potentially opening the way for the intervention on parchment and leather, whose preservation is a particularly challenging task.
Article
Full-text available
In this paper, we present the results of a literature survey concerning the methodology and criteria used for the evaluation of paper conservation interventions. Important issues that are reviewed include: Accelerated ageing: theoretical principles, most common methods, standards and conditions (temperature and relative humidity). Experimental setup: sample selection and preparation, planning of the experiments. Methods for the evaluation of paper properties: established methods already in use, various methods that have been sparingly used and methods that have never been used but have the potential to evolve and apply to specific problems of the evaluation. Criteria of effectiveness of the intervention. A selection of the most important relevant publications of the last 30 years and the methods yielded by the survey are presented in table format.
Article
Full-text available
Six fragments of different Yemenite manuscripts (three on parchment and three on paper) were analyzed by means of attenuated total reflectance Fourier transform infrared, micro-Raman and X-ray fluorescence spectroscopies. The combination of molecular and elemental techniques allowed the characterization of the conservation state of all the fragments, the identification of sizing agents and salts on the supports and the identification of the composition all red and black writing media. In particular, analysis of black inks provided interesting insights: independent of the substrate, all inks seemed to have identical composition, corresponding to rather well preserved high-quality iron tannic inks to which carbon black had not been added. However, in some samples, the most intense Raman peak of the ink was clearly shifted with respect to the typical bands of iron gall ink. Starting from the hypothesis that the shift could have been produced by the use of sources of tannin other than gallnuts, research was undertaken by preparing and characterizing seven different tannic inks. The experimental results confirmed the hypothesis of different tannin sources.
Chapter
Full-text available
The various aspects of natural and accelerated ageing of cellulose and paper are presented and discussed. Accelerated ageing constitutes the major methodological tool for the studying of cellulose and paper ageing. The topics include: • The correlation of natural and accelerated ageing. Methodology of research, results up to date. • The chemistry of ageing: chain scission, oxidation, crosslinking. Influence of environmental factors (temperature and relative humidity), moisture content, impurities and additives, pH, light, pollution etc. • The effects on the physicochemical, mechanical, optical and structural properties of cellulose. Changes in water absorption (hornification), porosity and crystallinity. • The ageing kinetics. Chemical and property kinetics. Courses of ageing under different conditions. Autocatalysis in sealed vessels. Kinetic models. The applicability of the Arrhenius studies for paper permanence predictions and the related controversy are discussed. • The methods of accelerated ageing. Standards. Dry and humid ageing, sealed enclosures. • Applications of accelerated ageing: permanence predictions, classification of papers according to their permanence, performance standards for testing for paper permanence, evaluation of paper conservation interventions.
Article
The multi analytical study of historical objects is a complex part from an instrument which can help the restorers to recognize the materials, as well as their state of conservation, facilitating the selection of the appropriate method of conservation and/or restoration. This study concentrates the potential use of non-destructive and non-invasive techniques (optical microscopy, X-ray fluorescence, Infrared microscopy, Raman spectroscopy, as well as some methods used to evaluate the general characteristics, such as surface pH and UV photography) in deciphering the long-gone recipes for paper and inks manufacturing from 17th century Transylvania, multicultural centre of erudition. Beside the information obtained regarding the paper support (surface pH, details regarding the cellulose fibers, as well as potential fillers used for paper manufacturing, as well as the nature of the stains present on the document), the performed study reveals a very interesting detail regarding the inks used, respectively the use of mixed recipes, including more than a single pigment.
Article
This work studies the different materials used in the production of Argentine postage stamps from 1888 to 2016 and explains how the use of these materials has changed over time, thus contributing to knowledge of the national philatelic heritage. Analyses of more than 40 Argentine postage stamps were carried out non-invasively in situ without the need for prior preparation, using portable X-ray fluorescence spectroscopy (p-XRF) and Fourier transform infrared spectroscopy with attenuated total reflectance (FTIR-ATR). Paper, ink, coatings, and adhesives were analysed and the period of use of each material was established. Some notable results include the continuous use of Prussian blue until its replacement by an organic copper phthalocyanine pigment. In addition, it was possible to establish the substitution date of gum arabic as an adhesive by PVA. In general, the variation of the materials used was accompanied by changes in printing techniques. This is the first time that information on the materiality of these historical-artistic objects is published, contributing to the knowledge and conservation of the philatelic heritage of the Argentine Republic.
Article
Four kinds of fibers with 11 traditional natural dyes were measured using a portable spectrometer equipped with optical fibers working in reflectance mode (fiber optic reflectance spectroscopy, FORS) in the ultraviolet to near-infrared (NIR) regions. The absorption spectra of Kubelk–Munk transformation in ultraviolet–visible (UV–vis) region were demonstrated to be valid for analysis of dyes on textiles and the characteristic absorption spectra of fiber in near-infrared region provide information to discriminate the type of fibers. The technique was applied to examine a collection named of ‘Lohan Rubbing’ of Qing Dynasty from Tibet Museum, then the established spectra library was further applied to analyze the collection. With the comparison to the references of spectra library, sappanwood, madder, indigo and amur-cork tree were successfully identified in the inlay colored textile. The mixture of sappanwood and indigo for the purple color, amur-cork tree and indigo for the green color were detected. The application of portable fiber optic reflectance spectroscopy provides a rapidly and non-invasive way for natural dye identification in historical textiles and it is beneficial to large-scale on-site survey.
Article
X-ray analytical techniques are increasingly used to study manuscripts and works of art on paper, whether with laboratory equipment or synchrotron sources. However, it is difficult to anticipate the impact of X-ray photons on paper and cellulose-based artefacts, particularly due to the large variety of their constituents and degradation levels, and to the subsequent material multiscale heterogeneity. In this context, this work aims at developing an analytical approach to study the modifications in paper upon SR X-ray radiation using analytical techniques, which are fully complementary and highly sensitive, yet not frequently used together. At the molecular scale, cellulose chain scissions and hydroxyl free radicals were measured using chromatographic separation techniques (SEC-MALS-DRI and RP-HPLC-FLD-DAD), while the optical properties of paper were characterized using spectroscopy (UV luminescence and diffuse reflectance). These techniques showed different sensitivity towards the detection of changes. The modifications in the cellulosic material were monitored in real time, within a few days, and up to two years following the irradiation in order to define a Lowest Observed Adverse Effect Dose (LOAED). As paper is a hygroscopic material, the impact of the humidity in the environment was studied using this approach. Three levels of moisture content in the paper, achieved by conditioning the samples and irradiating them at different relative humidity, were studied (0%, 50%, 80% RH). It was shown that very low moisture content accelerated the molecular and optical modifications.
Article
Microgel particles have emerged in the last few years as a favourite model system for fundamental science and for innovative applications ranging from industrial to biomedical fields. Despite their potentialities, no works so far have focused on the application of microgels for cultural heritage preservation. Here we show their first use for this purpose, focusing on wet paper cleaning. Exploiting their retentive properties, microgels are able to clean paper ensuring more controlled water releasing from the gel matrix, in analogy to their macroscopic counterpart, i.e., hydrogels. However, differently from these, the reduced size of microgels makes them suitable to efficiently penetrate in the porous structure of the paper and to easily adapt to the irregular surfaces of artefacts. To test their cleaning abilities, we prepare microgels made of Gellan gum, a natural and widespread material already used as a hydrogel for paper cleaning, and apply them to modern and ancient paper samples. Combining several diagnostic methods, we show that microgels performances in the removal of cellulose degradation by-products for ancient samples are superior to commonly employed hydrogels and water bath treatments. This is due to the composition and morphology of ancient paper, which facilitates microgels penetration. For modern paper cleaning performances are at least comparable to the other methods. In all cases, the application of microgels takes place on a time scale of a few minutes, opening the way for widespread use as a rapid and efficient cleaning protocol.
Article
The conservation and restoration of paper artworks play a fundamental role in the field of our Cultural Heritage. In this contest, the characterization of paper composition as well as degradation state is fundamental to determine the suitable restoration and conservation processes for paper artworks. In this work, we present an interdisciplinary study focalized on the not-invasive characterization of a group of 16 precious Arabic-Christian manuscripts (originating from different regions of the Arabian Peninsula used in Christian environment) of XIII century, collected in the Vatican Library (Biblioteca Apostolica Vaticana – BAV, Vatican City). The aim of this study is focused onto the characterization of papers and inks compositions of these manuscripts, in order to understand if there are similarity between them, and in same way, to obtain information about the provenience of them. For this goal, several analytical techniques were applied by using portable instrumentation directly in the restoration laboratory of BAV, such as Infrared Reflectography, X-ray fluorescence and colorimetry. In addition, High Performance Liquid Chromatography with UV/VIS detection and Fourier Transform Infrared Spectroscopy were applied for the evaluation of the composition and the conservation status of these books by the analyses of the material, removed by a sampling method based on the sponges mainly used for cleaning of paper artworks. Crossing the obtained results, we can characterize the composition of the paper and the inks, used in the various manuscripts. They present the same characteristics in terms of chemical composition, not linked on the region where the book was found, underlining that the used protocol for the paper and its production were the same in the Arabic Peninsula.
Article
As paper is the base for (printed) documents-including bogus documents-it is often the subject of forensic investigations. Its properties depend on interactions between and within cellulose chains, mainly assigned to inter-and intramolecular hydrogen bonds. During paper degradation, the degree of polymerization of the cellulose chain changes. Vibrational spectroscopy has already been widely applied to resolve cellulose structure, crystalline phases and hydrogen bonds networks. The aim of the present research was to evaluate the possibility of differentiating between degraded papers by spectroscopic techniques. Five paper samples were artificially aged in a climatic chamber under 65% relative humidity in air at 90 °C for various periods up to 35 days. The conditioned samples – of differing durations of ageing – were then analyzed using infrared and UV/VIS spectroscopy. It was observed that the paper samples differed in the range 1000–1120 cm⁻¹, 2860-2950 cm⁻¹ and 1300-1380 cm⁻¹ in infrared as a function of time of aging. Differences were also found in UV/VIS spectra, concerning bands of intensity of ca. 280 and 350 nm. 2D correlation analysis as well as the PCA method have allowed to distinguish between selected paper samples, through the specificity of the aging process that runs in them.
Article
The discoloration of paper, due to the development of oxidized groups acting as chromophores in its chief component, cellulose, is responsible for severe visual degradation of works of art on paper. By adopting a diagnostic method based on in situ non-invasive optical reflectance spectroscopy and time-dependent density functional theory ab initio calculations, it is possible to describe and quantify the chromophores in cellulose fibers in a non-destructive way. In order to recover the absorption coefficient of cellulose fibers from reflectance measurements a specific approach based on the Kubelka-Munk theory was applied. The concentrations of carbonyl groups acting as chromophores were obtained by fitting the experimental optical absorption spectra to those simulated by using ab initio calculations. This method was applied for monitoring the restoration interventions of two great format engravings Le Nozze di Psiche and Gesù Cristo e l’adultera by Diana Scultori (1547-1612), as well as a contemporary artwork by Renato Guttuso, Bozzetto per Crocifissione (dated 1940). All artefacts were affected by chromatic deterioration due to a strong oxidation of the paper. Results quantified the decreasing of chromophores concentration after washing and reducing treatments evidencing the different behavior of the carbonyl groups as a function of the specific protocol performed.
Article
Liquid chromatography has been widely employed in the analysis of materials in Heritage Science, due to its ease of use and relatively low-cost, starting from thin layer chromatography of organic binders in paintings, of archaeological waxes and resins, and finally of natural dyes. High performance systems employing analytical columns containing packed stationary phases gradually supplanted thin layer chromatography (TLC) in the field, since the separation, detection and quantitation of specific species contained in a sample in the field of Cultural Heritage requires selective, sensitive and reliable methods, allowing for analysing a wide range of samples, in terms of analyte types and concentration range. Today, the main applications of High-Performance Liquid Chromatography in this field are related to the separation and detection of dyestuffs in archaeological materials and paint samples by reversed-phase liquid chromatography with suitable detectors. Proteomics and lipidomics are also gaining momentum in the last decade, thanks to the increased availability of instrumentation and procedures. In this chapter, principles and theory of liquid chromatography will be presented. A short review of the instrumentation needed to perform an analysis will be provided and some general principles of sample preparation revised. More details on the detection systems, the chromatographic set-ups and specific sample treatment strategies will be provided in the individual sections dedicated to the applications to Heritage Science of the main types of liquid chromatographic techniques. In particular, the applications of thin layer chromatography will be shortly described in paragraph 4.1. The applications of Reverse Phase High Performance Liquid Chromatography (RP-HPLC) will be discussed in detail in paragraph 4.2, including the analysis of natural and synthetic dyes and pigments and the profiling of lipid materials. The possibility to perform proteomic analysis will be presented and a link to the relevant Chapter in this book provided. The most important and promising applications of ion exchange chromatography (IC) will be discussed in paragraph 4.3. Finally, size exclusion and gel permeation chromatography (GPC) will be presented in paragraph 4.4, including applications to the study of polymeric network formation in paint binders, of the phenomena related to the depolymerisation of cellulose in paper and of cellulose and lignin in wood samples. The possibility to study synthetic polymers as artists’ materials and restorers’ tools by size exclusion (SEC) or gel permeation (GPC) will also be introduced. In the conclusions, future perspectives of liquid chromatography in Heritage Science will be briefly discussed.
Article
Control over the mechanical properties of cellulose-based artifacts (e.g. paper) is highly important in cultural heritage science. Especially, a non-aqueous method that does not cause swelling but can be applied to either single paper sheets or bound cellulose items (e.g., books) without any preselection is currently needed. Herein, we present a new multilayer deposition method that can simultaneously deposit alkaline reserve and improve the mechanical properties of historic wood pulp (HWP) paper, which often suffers from high fragility and brittleness. Alkaline nanoparticles (magnesium hydroxide Mg(OH)[Formula presented]NPs) stabilized by hydrophobic cellulose derivative i.e., trimethylsilyl cellulose (TMSC) in hexamethyldisiloxane (HMDSO) are prepared and deposited in the form of multiple layers on HWP paper by a technically effortless dip coating procedure. An enhanced and irreversible deposition of Mg(OH)2 NPs–TMSC and an alkaline reserve (AR) up to 4% (139 meq[OH[Formula presented]]/100g) are achieved as revealed by infrared spectroscopy and back-titration measurement. The tensile strength of uncoated HWP paper (1.6 MPa) is increased to 5.5 MPa after coating with Mg(OH)[Formula presented]NPs/TMSC (before aging) and then to ca 9 MP (after accelerated aging). In the latter case, the TMSC is transformed to cellulose by cleaving of O–Si bonds. The surfaces are evenly covered with thin and transparent coatings of hydrophobized nanoparticles as demonstrated by electron scanning microscopy and contact angle measurements.
Article
Disposable non-invasive and compatible real time monitoring tool was developed in order to follow the cleaning process of paper artwork directly in situ. This tool was based on a biocompatible cleaning hydrogel coupled with flow electrochemical diagnostic tool, suitable to verify in situ and in a simple way the assessment of degradation of artwork and the efficiency of cleaning process. In this paper, the results obtained by applying this tool on a great format artwork with a lining as support, “Le Nozze di Psiche”, engraved by Diana Scultori, printed in 1613, are reported. This opera was affected by a structural and chromatic deterioration due to a strong oxidative degradation. Such deterioration was probably accelerated by the adhesive (a mixture of starch paste and animal glue) used in a previous lining intervention. In this case, the cleaning agents used are rigid hydrogels of Gellan gum, modified with hydrolytic enzymes. By using the flow sampling system, all materials removed by the gel was carried up to a thin layer cell containing a selective electrochemical biosensors, suitable to monitor both treatments, the cleaning process and the removal of lining. These were monitored, allowing understanding when both processes were completed, thus avoiding lengthy and unnecessary cleaning applications. The effectiveness of cleaning with Gellan gel was assessed quantitatively by using non-invasive optical reflectance spectroscopy by a portable instrumentation, elaborating data with an improved version of the Kubelka-Munk theory in order to recover the absorption coefficient of the cellulose fibers of “Le Nozze di Psiche”. The concentration of oxidized groups acting as chromophores was obtained by comparing the experimental optical absorption spectra to those simulated computationally by using TDDFT-based calculations. By following the cleaning with Gellan gel the results indicate a large decrease of the concentration of degradation product of cellulose. Moreover, chromatographic analysis were carried out in order to evaluate the amount of acid compound, produced during the aging and present on the graphic artwork, using the Gellan gel after cleaning step. The results obtained from the restoration of “Le Nozze di Psiche” have allowed the restorers to evaluate innovative methods for cleaning treatment of paper artworks with a highly specialized scientific-diagnostic approach.
Article
This research aims to determine the degree of implementation at the international level of the various paper conservation methods found in the literature. Participating organizations in the survey mainly include national libraries, archives and museums, practicing paper conservation. The results of the survey indicate that the types of objects treated by the majority of the participating organizations consist mainly of manuscripts, archival material, books, maps, topographical drawings and photographic material. The vast majority of the organizations implement at least one of the methods associated with every distinct category of paper conservation methods. Nevertheless, only a limited number of methods per category/step are popular and are implemented to a noteworthy degree. Organizations tend to avoid the extensive usage of chemicals, and apply simple and well-established methods, such as dry cleaning, washing in water, deacidification with calcium hydroxide and paper mending with Japanese paper and paste, instead of complex conservation methods. The results indicate that several deprecated methods are still in use, especially for bleaching. Finally, the wide implementation of many methods that appear to be in use according to the literature review is not documented by the survey results. The three answers with the highest percentages per paper conservation category/subcategory are presented in table form.
Article
An investigation into (and explanation for) the remarkable permanence of early European papers made by hand in accordance with Italian practice is presented. The use of added lime ("addita calce") during the beating process (referred to by F.M. Grapaldo in his description of the Italian technique, c. 1494, and in the late sixteenth-century Regensburg Regulations) is shown to be the responsible cause. The early Italian technology is described and comparisons are made with modern machine-production of permanent papers.
Chapter
This chapter discusses the characteristics of several adhesive types. Alloyed or modified (Two-Polymer) adhesives are important as structural adhesives, especially in metal bonding. They are comprised of a thermosetting and a thermoplastic polymer, including certain elastomers. Anaerobic Adhesives/Sealants are acrylate acid diesters (polyester-acrylic). They are essentially monomeric thin liquids that polymerize to form a tough plastic bond when confined between closely fitting metal joints. Cyanoacrylate adhesives are marginally thermosetting. They form strong thermosetting bonds between many materials without heat or an added catalyst. They are particularly useful in bonding metal to nonmetal. Elastomeric adhesives are natural or synthetic rubber-based materials, usually with excellent peel strength but low shear strength. Their resiliency provides good fatigue and impact properties. Epoxy-polysulfide adhesives are products of reaction between an epoxy resin and liquid polysulfide polymer, usually catalyzed by an additional tertiary amine. Phenolformaldehyde adhesives, are condensation products of formaldehyde and a monohydric phenol. Phenolics are also among the lowest-cost adhesives and may be formulated as water dispersions, to allow penetration into the cell structure of wood that is important for the formation of permanent bonds. Water-based additives are prepared from materials that can be dispersed or dissolved only in water. Some of these materials are the basis of solvent-based adhesives and are the principal materials used for liquid adhesive formulations.
Article
The removal of old glue from paper artworks is of paramount importance for the preservation of its integrity during the restoration process. Wet cleaning is one of the traditional methods, although, it may cause damages on artworks. In this work, an advantageous alternative method, based on the use of a rigid hydrogel, for a simple and localized removal of starch paste from paper supports is presented. The use of an appropriate hydrogel allows to overcome many of the problems faced by restorers minimizing damages, through a controlled release of water to the artwork, and a simple and not invasive application and removal. At the same time, the specific and targeted enzyme activity leads to a significant reduction in the application time of the cleaning procedure. In this context, experiments were carried out applying Gellan hydrogel carrying α-amylase enzyme on several paper samples soiled with starch paste. To assess the cleaning efficacy of the proposed hydrogel, a multidisciplinary approach, by means of spectroscopic techniques, scanning electron microscopy, chromatographic analysis and pH investigations, has been used.
Article
In this paper, we present a new noninvasive and nondestructive approach to recover scattering and absorption coefficients from reflectance measurements of highly absorbing and optically inhomogeneous media. Our approach is based on the Yang and Miklavcic theoretical model of light propagation through turbid media, which is a generalization of the Kubelka-Munk theory, extended to accommodate optically thick samples. We show its applications to paper, a material primarily composed of a web of fibers of cellulose, whose optical properties are strongly governed by light scattering effects. Samples studied were ancient and industrial paper sheets, aged in different conditions and highly absorbing in the ultraviolet region. The recovered experimental absorptions of cellulose fibers have been compared to theoretical ab initio quantum-mechanical computational simulations carried out within time-dependent density functional theory. In this way, for each sample, we evaluate the absolute concentration of different kinds of oxidized groups formed upon aging and acting as chromophores causing paper discoloration. We found that the relative concentration of different chromophores in cellulose fibers depends on the aging temperature endured by samples. This clearly indicates that the oxidation of cellulose follows temperature-dependent reaction pathways. Our approach has a wide range of applications for cellulose-based materials, like paper, textiles, and other manufactured products of great industrial and cultural interest, and can potentially be extended to other strongly absorbing inhomogeneous materials.
Article
The discoloration of ancient paper, due to the development of oxidized groups acting as chromophores in its chief component, cellulose, is responsible for severe visual degradation in ancient artifacts. By adopting a non-destructive approach based on the combination of optical reflectance measurements and time-dependent density functional theory ab-initio calculations, we describe and quantify the chromophores affecting Leonardo da Vinci's iconic self-portrait. Their relative concentrations are very similar to those measured in modern and ancient samples aged in humid environments. This analysis quantifies the present level of optical degradation of the Leonardo da Vinci's self-portrait which, compared with future measurements, will assess its degradation rate. This is a fundamental information in order to plan appropriate conservation strategies.
Article
Paper is an important material for many applications. During the centuries, it has been the most widely used writing support and therefore paper degradation is a major issue for cultural heritage. The main component of paper is cellulose, one of the most abundant biomaterials on Earth. Cellulose oxidation is mainly responsible for the yellowing of the ancient samples, through the formation of chromophores. In order to investigate this issue and the chromophores’ role, we exploit the optical properties combining non-destructive experiments and theoretical calculations based on ab-initio techniques. In this paper, we illustrate the method and show its application to three ancient paper samples. The procedure we describe is a precious tool for cultural heritage preservation: indeed, the approach we present is based on non-invasive and non-destructive measurements that allows a microscopic understanding of cellulose-based artifacts degradation.
Article
To better understand the degradation of cellulose upon the formation of a tideline at the wet-dry interface when paper is suspended in water, the production of chemical species involved in oxidation reactions was studied. The quantitation of hydroperoxides and hydroxyl radicals was carried out in reverse phase chromatography using triphenylphosphine and terephthalic acid, respectively, as chemical probes. Both reactive oxygen species were found in the tideline immediately after its formation, in the range of micromoles and nanomoles per gram of paper, respectively. The results indicate that hydroxyl radicals form for the most part in paper before the tideline experiment, whereas hydroperoxides appear to be produced primarily during tideline formation. Iron sulfate impregnation of the paper raised the production of hydroperoxides. After hygrothermal aging in sealed vials the hydroxyl radical content in paper increased significantly. When aged together in the same vial, tideline samples strongly influenced the degradation of samples from other areas of the paper (multi-sample aging). Different types of antioxidants were added to the paper before the tideline experiment to investigate their effect on the oxidation reactions taking place. In samples treated with iron sulfate or artificially aged, the addition of Irgafos 168 (tris(2,4-ditert-butylphenyl) phosphate) and Tinuvin 292 (bis(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate and methyl 1,2,2,6,6-pentamethyl-4-piperidyl sebacate) reduced the concentration of hydroperoxides and hydroxyl radicals, respectively. Tinuvin 292 was also found to considerably lower the rate of cellulose chain scission reactions during hygrothermal aging of the paper.
Article
Collectables on paper contain a large number of components of varying degrees of stability. The factors that cause these to deteriorate include oxidation, acid hydrolysis, air pollutants and water. Deacidification is often used by conservators and there are beneficial effects from the introduction of Mg2+ and Ca2+; however, excessive alkalinity must be avoided. There are many mechanisms for the development of discolouration in paper. Several examples of ageing effects of inks and pigments are considered.
Article
The effect of three washing methods is compared with regard to the removal of acid compounds from aged paper: immersion washing, blotter washing, and suction table washing with the aid of ultrasonic mist. The authors identify and quantify the organic acids (acetic-, lactic-, malic-, oxalic- and succinic acid) and inorganic anions (Br(-), Cl(-), SO(4)(2-), NO(2)(-)) present in the wash water after the end of the washing operation. In this study, immersion washing was most effective, followed by the application of ultrasonic mist on the suction table in the case of thin and porous papers. Suction table washing was ineffective for the treatment of thick and dense papers. Blotter washing showed the lowest effectiveness with regard to the removal of organic acids, especially oxalic acid, from paper.
Article
The possible mechanisms of autoxidative degradation of cellulose are listed and their importance in degradation of paper during ageing is analysed. It is pointed out that autoxidative reactions are accelerated in alkaline media, In addition, certain transition metal ions as well as groups, which are capable of autoxidation, also promote the free radical reactions. Understanding of the main degradative routes may help us in choosing the right conservation treatment for certain paper,as well as form the basis for further stabilization studies.
Article
In this work, we present a wide-range spectrochemical analysis of the degradation products from naturally aged paper. The samples obtained from wash waters used during the de-acidification treatment of leaves from a 16th-century-printed book were analysed through NMR, IR, Raman UV/Vis, EPR and X-ray fluorescence (XRF) spectroscopy and HPLC-MS and inductively coupled plasma (ICP) analysis. By these methods we also studied some of the previous samples treated by acidification (sample AP) and catalytic hydrogenation (sample HP). Crossing all the data, we obtained precise indications about the main functional groups occurring on the degraded, water-soluble cellulose oligomers. These results point out that the chromophores responsible for browning are conjugated carbonyl and carboxyl compounds. As a whole, we show that the analysis of wash waters, used in the usual conservation treatments of paper de-acidification, gives much valuable information about both the conservation state of the book and the degradation reactions occurring on the leaves, due to the huge amount of cellulose by-products contained in the samples. We propose therefore this procedure as a new very convenient general method to obtain precious and normally unavailable information on the cellulose degradation by-products from naturally aged paper.
Article
The oxidative route of cellulose degradation during artificial ageing of paper in humid air (RH 59%, 90 °C) has been followed by FTIR and UV/vis spectroscopic methods providing a vibrational pattern of carbonyl groups and electronic transitions of chromophores, respectively. Conjugated ketonic groups with vibrational modes around 1610 cm−1 were correlated to the chromophores emerging in the range between 230 and 440 nm detected by UV/vis spectroscopy. The FTIR spectra of degraded cellulose were interpreted using quantum-chemical modelling based on the DFT method performed on the model molecule of cellopentose. Based on this carbonyl FTIR bands were assigned to specific vibrations. The UV/vis and FTIR correlations together with the theoretical charge distribution rationalized the possible mechanism of oxidative glycosidic bond cleavage.
Article
The degradation of cellulose in paper due to the formation of a tideline at the wet-dry interface when paper is suspended in water was explored. SEC/MALS was used to assess the molar mass, while ICP/MS, SEM/EDS and CE/UV provided a qualitative and quantitative analysis of the elements and inorganic ions present in the paper. Immediately after the formation of the tideline, no significant depolymerization was observed at the wet-dry interface, despite the accumulation of water soluble brown and/or fluorescent degradation compounds and salts containing sodium, chlorine, sulfur and calcium. Various artificial aging configurations were applied to the paper with tidelines to evaluate the effect of the material accumulated at the wet-dry interface on the long-term stability of paper. The decrease in the molar mass of cellulose above, at and below the tideline) differed depending on the type of aging, i.e. whether the entire sheet of paper was aged or whether small amounts of paper from the different areas were sampled and aged, individually or together, which evidences a complex degradation pathway. In the former aging configuration the material accumulated in the tideline affected the degradation of the tideline area to the same extent or more than the other areas. When the different areas of the paper sheet were sampled and aged together, it was found that the presence of the tideline clearly affected the degradation of the other paper areas. Conversely, in that case, cellulose within the tidelines was the least degraded. The area below the tideline, through which the water migrated, showed the most significant degradation.
Article
The study presents an overview of the chromatographic (SEC), spectroscopic (FTIR, UV/VIS), viscometric (DP) and chemical methods (titration, pH) used for the evaluation of the degradation progress of various kinds of paper under various conditions. The methods were chosen to follow different routes of paper degradation. Model paper samples represented boundary paper types from pure cellulose cotton paper, through softwood to low quality acidic, sized groundwood paper The accelerated ageing conditions were adjusted to achieve maximum effect (climatic chamber RH 59%, 90oC) and also to mimic the environment inside books (closed vials). The results were settled on the literature data on the degradation mechanisms and compared in terms of the paper types and ageing conditions. The estimators of coupled de-polymerisation and oxidation have been proposed based on the correlation between SEC, UV/VIS and titrative coppper number determination. The overall oxidation index derived from FTIR results was shown to correlate with the summary –CHO and –COOH concentration determined by titrative methods.
Article
For many centuries paper was the main material for recording cultural achievements all over the world. Paper is mostly made from cellulose with small amounts of organic and inorganic additives, which allow its identification and characterization and may also contribute to its degradation. Prior to 1850, paper was made entirely from rags, using hemp, flax and cotton fibres. After this period, due to the enormous increase in demand, wood pulp began to be commonly used as raw material, resulting in rapid degradation of paper. Spectroscopic techniques represent one of the most powerful tools to investigate the constituents of paper documents in order to establish its identification and its state of degradation. This review describes the application of selected spectroscopic techniques used for paper characterization and conservation. The spectroscopic techniques that have been used and will be reviewed include: Fourier-Transform Infrared spectroscopy, Raman spectroscopy, Nuclear Magnetic Resonance spectroscopy, X-Ray spectroscopy, Laser-based Spectroscopy, Inductively Coupled Mass Spectroscopy, Laser ablation, Atomic Absorption Spectroscopy and X-Ray Photoelectron Spectroscopy.
Article
A methodology for capillary electrophoresis/electrospray ionisation mass spectrometry (CE/ESI-MS) was developed for the simultaneous analysis of degradation products from paper among two families of compounds: low molar mass aliphatic organic acids, and aromatic (phenolic and furanic) compounds. The work comprises the optimisation of the CE separation and the ESI-MS parameters for improved sensitivity with model compounds using two successive designs of experiments. The method was applied to the analysis of lignocellulosic paper at different stages of accelerated hygrothermal ageing. The compounds of interest were identified. Most of them could be quantified and several additional analytes were separated.
Article
Unabridged republication of the second edition of this work as published by Alfred A. Knopf, New York Incluye bibliografía e índice
Article
Brown lines were generated at the wet-dry interface on Whatman paper No. 1 by suspending the sheet vertically in deionized water. Formic acid and acetic acid were quantified in three areas of the paper defined by the wet-dry boundary (above, below, and at the tideline) using capillary zone electrophoresis with indirect UV detection. Their concentration increased upon accelerated aging of the paper and was highest in the tideline. The hydroperoxides have been quantified using reverse phase high performance liquid chromatography with UV detection based on the determination of triphenylphosphine oxide produced from the reaction with triphenylphosphine, and their highest concentration was found in the tideline as well. For the first time, it was shown that various types of hydroperoxides were present, water-soluble and non-water-soluble, most probably in part hydroperoxide functionalized cellulose. After accelerated aging, a significant increase in hydroperoxide concentration was found in all the paper areas. The molar masses of cellulose determined using size-exclusion chromatography with multiangle light scattering detection showed that, upon aging, cellulose degraded significantly more in the tideline area than in the other areas of the paper. The area below the tideline was more degraded than the area above. A kinetic study of the degradation of cellulose allowed determining the constants for glycosidic bond breaking in each of the areas of the paper.
Papermaking and printing
  • Jixing
Exploring ATR Fourier transform IR spectroscopy with chemometric analysis and laser scanning microscopy in the investigation of forensic documents fraud
  • Farid
Optical spectroscopy of ancient paper and textiles
  • M Missori
M. Missori, Optical spectroscopy of ancient paper and textiles, Il Nuovo Cimento C, 39(2) (2016) 293.