1,720,997 research outputs found
Calcium oxalate films on works of art: A review
No full textThis work presents a review of the findings of calcium oxalate films, a widespread decay phenomenon recovered on stone and other substrates (mortars, wall and easel paintings, written materials, glass). The specific attention given to the issue in the 1990s has decreased, although articles have documented films until the present day. The review provides critical insights into the literature, focusing on the general properties of films, numerous case studies, the instrumental techniques used to characterise and date films, insights into the possible origin of the decay phenomenon, and an evaluation of the protective role of calcium oxalate layers. The practice of creating artificial films on stone surfaces for protective purposes is also considered. An evaluation of the literature over the last few decades shows various open issues. The origin is still up for debate, and the issue is still of major concern to conservation scientists, conservators, and restorers. The scientific community tends to attribute a biological origin to these films, however further studies are needed to study exactly how they form, focusing for example on simulation tests of the chemical and atmospheric pathway. How these films protect the artwork in terms of the mechanical properties of the surface underneath deserves more study. This would also help restorers to reproduce the calcium oxalate. The bibliography highlights the prevalence of calcium oxalate findings in the Mediterranean Basin and the formation of the least stable form, i.e. weddellite, which has yet to be explained
Contribution of thermal analysis in the characterization of lime-based mortars with oxblood addition
No full textIn this study, thermogravimetry and differential scanning calorimetry (TG-DSC) along with X-ray diffraction analysis (XRD) and Fourier transform infrared (FTIR) spectroscopy in attenuated total reflectance (ATR) mode, were performed on a series of lime mortar specimens with oxblood addition. Calculated TG weight loss showed that at initial stages, oxblood addition could slow down the carbonation process. Specimens containing oxblood showed two peaks above similar to 550 degrees C in their DSC curves, and the combination of TG-DSC and ATR techniques allowed to speculate that the first peak (at lower temperatures) could correspond to the decomposition of CaCO3 at a lower degree of crystallinity (e.g. amorphous calcium carbonate (ACC), aragonite, vaterite), while the second peak (at higher temperatures) corresponded to the decomposition of calcite. Additionally, XRD and ATR results indicated that ACC was formed in the specimens containing oxblood at a first stage, and as time progresses, ACC could transform to vaterite and then to calcite
Direct analysis of volumetric absorptive micro sampling (VAMS) devices by ATR-FT-MIR and chemometric analysis: a new challenge
No full textVolumetric Absorptive Micro Sampling (VAMS) strategy, in its simplicity, has made a major contribution to the development of at-home sampling strategies. Mainly used for blood analysis, it absorbs a fixed volume of sample. Folded into its cover, the VAMS device dries, and it can be sent to a lab via mail. In this article, for the first time in our knowledge, we explored the possibility to use this sampling strategy to expand the scope of VAMS to other samples than clinical ones. In this way we used VAMS to sample and analyze milk, which is one of the most important and analyzed samples all over the world. VAMS devices were employed to sample commercial milk samples from Italy, Switzerland and Spain, and for the first time the device was directly analyzed by ATR-FT-IR to predict protein, carbohydrate and fat content in the milk samples. Samples were collected in different sessions from different persons and analyzed by different lab operators to include in the models these sources of variability. Multivariate regression was used to correlate ATR-FT-IR spectra with the investigated properties: models were validated with external validation
Impianto sperimentale alimentato da pompa di calore elioassistita
No full textIl lavoro - sviluppato dal Dipartimento di Energetica dell'Università dell'Aquila nell'ambito di un programma di ricerca scientifica - ha due obiettivi: validare un sistema edificio-impianto a pannelli radianti a pavimento; studiare i rapporti ottimali di funzionamento tra l'apparato di captazione dell'energia solare e la pompa acqua-acqua che rende meglio utilizzabile il calore ottenuto dall'accumulo di energia solare
Application of Different Fourier Transform Infrared (FT-IR) Methods in the Characterization of Lime-Based Mortars with Oxblood
No full textOrganic compounds have frequently been added into lime mortars for property modifications, in order to satisfy various functional needs in building techniques. This study applies Fourier transform infrared (FT-IR) spectroscopy in transmission, reflection, and attenuated total reflection (ATR) modes to characterize lime-based mortar specimens containing oxblood, which has been used as additive as a common practice of long history in many parts of the world. The specimens were prepared basing upon a 19th-century Italian historic recipe, with the intention to have a better understanding on the possible characteristics of such mortars. Thermal analysis, color measurement, and static contact angle test were also used. After curing, the specimens show a distinctive dark-red color on the top surface, which is different from the bulk. Color measurements on the surface suggest that this color was formed at an early stage and was able to maintain stable for a relatively long period of time. Both transmission and reflection FT-IR confirm the preferential accumulation of proteins on the top surface, which should have induced their water repellency according to the static contact angle test. In addition, specimens show weaker calcite bands in FT-IR transmission, reflection, as well as ATR spectra; the pattern of ATR spectra after the thermal analysis to 500 degrees C suggests the formation of amorphous calcium carbonate, which is related to the presence of oxblood
Gypsum based mixes for conservation purposes: Evaluation of microstructural and mechanical features
No full textThis paper presents the study of four gypsum mixtures, focusing on the role of both inorganic and organic additives and on the micro-structural features and mechanical properties. Additives have been chosen among those most reported in historical recipes, for example magnesia, lime putty, rabbit glue. The selected mixes refer to gypsum-based materials used in artworks manufacture, such as plasters, mouldings, stuccoworks, pastiglia. Blank reference materials were prepared on purpose according to the specific recipe, in order to verify the final composition and to highlight the hardening mechanisms and the formation of setting compounds. The chemical composition was related to workability properties and final mechanical resistance and the action of additives as retardants was studied with interesting results. For instance, MgO imparts good properties to the mechanical features, especially with regard to the compressive strength characteristics
Thin Lead Sheets in the Decorative Features in Pavia Charterhouse
No full textThe facade of the church of the Pavia Charterhouse, built at the end of the 15th century, shows outstanding decorative features made of different stone materials, such as marbles, breccias and sandstones. Magnificent ornamental elements are made of thin lead sheets, and some marble slabs are inlaid with them. Metal elements are shaped in complex geometric and phytomorphic design, to form a Greek fret in black contrasting with the white Carrara marble. Lead pins were fixed to the back of the thin lead sheets with the aim of attaching the metal elements to the marble; in so doing the pins and the lead sheets constitute a single piece of metal. In some areas, lead elements have been lost, and they have been substituted with a black plaster, matching the colour of the metal. To the authors' knowledge, this kind of decorative technique is rare, and confirms the refinement of Renaissance Lombard architecture. This work reports on the results of an extensive survey of the white, orange and yellowish layers, which are present on the external surface of the lead. The thin lead sheets have been characterized and their state of conservation has been studied with the aid of Optical Microscopy, SEM-EDS, FTIR and Raman analyses. Lead sulphate, lead carbonates and oxides have been identified as decay products
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