1,721,055 research outputs found
Alcoholic deacidification and simultaneous deacidification-reduction evaluated after artificial and natural aging
No full textCellulose oxidative and hydrolytical degradation is one of the greatest problems for the conservationof paper supports. To contrast these degradation processes, both deacidification and reduction of theoxidized functions are needed. Dealing with original documents, it is often impossible to perform thetwo mentioned treatments in aqueous solutions and in a distinct subsequent way, because of the fragilityof the artifacts. After studying, in a separate way, an effective deacidifier (calcium propionate) solublein 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 paperpresents the chemical-physical results obtained by applying simple deacidification and simultaneousdeacidification-reduction on laboratory paper samples that were artificially aged and then re-measuredafter 10 and 15 years of natural aging. Results show that all alcoholic treatments are very effective: papersare stable also after a long period of both artificial and natural aging
Applications of XAS to Cultural Heritage
No full textX-rays Absorption Spectroscopy (XAS), for its features of high elemental selectivity, spatial resolution and non- destructivity, is a useful tool to study materials that form and decorate art object and to identify different degradation processes that can occur in works of art.In this study, it will be investigated a typical phenomenon of paper alteration called foxing, which appears as spots of variable dimensions generally colored from lemon yellow to dark-brown with sharp or irregular edges. Over the years, in fact, paper undergoes a series of alterations caused both by external and internal factors leading to cellulose degradation. This degradation is one of the greatest problems for the conservation of paper supports such as archival documents, books and artistic works. Degraded papers can show an evident fragility, a general yellowing and the formation of foxing spots that can, in some cases, not only damage the aesthetic of the object, but also compromise the readability of the text or the artistic works. The understanding of the different chemical processes underlying this degradation is of great importance to prevent further damage and to choose the appropriate restoration method. The foxing spots are generated by a complex mechanism based on the oxidation of iron or copper ions (chemical hypothesis) or on micro-organism based processes (microbiological hypothesis). By XAS we have investigated the chemical foxing and in particular the iron oxidation to be able to understand the formation mechanism of foxing. Measurements were performed on ID26 at ESRF on three different kinds of samples: A) Samples prepared and aged at ICPL (Istituto Centrale per la Patologia del Libro)to simulate the foxing spotsB) Samples prepared at ESRF during the experiment to follow the foxing formation mechanism from the beginningC) historical samples to compare the results obtained from the artificially prepared samplesFirst interesting results were obtained by these measurements varying the starting iron solution [Fe(II) and Fe(III) solution were used to simulate the foxing], the solution concentration and the artificial aging process. The foxing mechanism seems to be strongly dependent from the local structure of cellulose. Moreover, these measurements gave us important indications to plan new experiments to understand in depth this complex phenomenon.INFMeeting 2004 – Genova, 8-10 giugno 2004
Raman approach to investigate painted decorations and manufacture technology of fake Greek and Italic pottery: a contribution to authentication
No full textFaking manufacture of ancient pottery is a phenomenon connected to the circulation and trade of unknown archaeological objects, aimed at increasing the earnings of unscrupulous sellers. In this traffic, craftsmen use pseudoscientific skills to produce modern artefact inspired to the ancient ones for fraudulent purposes, mimicking the original materials and ancient manufacturing technologies. In the authentication of decorated ancient pottery, micro-Raman spectroscopy can provide a contribution to the study of constituent materials and manufacturing processes, thanks to the possibility of obtaining data in non-destructive mode or by micrometric samples and to its high sensibility to detect mineralogical and low-crystallinity phases in the decoration. This paper is focused on the characterisation of mineralogical compounds in black glazes and in polychrome overpainted decorations of pseudo-archaeological potteries, which embody different levels of forger’s skill, corresponding to an increasing gradualness in the interpretative complexity of the data acquired. For each case study, the specific contribution of micro-Raman spectroscopy to the characterisation of the surface decorations is highlighted, thus providing important clues about the counterfeiters modus operandi and suggesting its possible use as one of the tools for a multi-analytical authentication protocol for this kind of pottery artefacts
The Stability of Manganese Oxides Under Laser Irradiation During Raman Analyses: I. Compact Versus Channel Structures
No full textManganese oxides/oxyhydroxides (MnOx) are based on Mnn+O6 and Mnn+O4 polyhedra arranged such as to form compact, channel or layered structures. In geology, they are precious archives of past redox conditions for palaeoclimatic reconstructions; in material sciences, they are used for a variety of applications, from pigments to environmental remediation and energy storage. Thus, the fast, remote and non-destructive identification of MnOx is critical in several disciplines. Micro-Raman spectroscopy is often used for this purpose, although a systematic characterization of their stability under the laser beam is still lacking. In this work, we present our results on the behaviour of the most common MnOx having compact and channel structures when a 532-nm laser with intensity between ~23 μW/μm2 and ~36.8 mW/μm2 is used. The compact structures of manganosite (NaCl-like) and hausmannite (spinel-like) are stable up to ~36.8 mW/μm2. The stability of oxides with channel structures depends on channel size, charge of channel cations and valence state of Mn. Hausmannite is the final degradation product of all MnOx with channel structures, irrespective of the starting phase. Pyrolusite, manganite, hollandite and romanéchite are relatively stable under the laser beam, and the transition to the spinel structure occurs above 2.5 mW/μm2 while the degradation of cryptomelane and todorokite starts ~226 μW/μm2. The analysis of MnOx thus needs very accurate experimental conditions to avoid misleading and incorrect phase identifications. Based on our data, we propose an analytical protocol for a proper characterization of these minerals via Raman spectroscopy
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