Hyperspectral image reconstruction of heritage artwork using RGB images and deep neural networks

The application of our research is in the art world where the scarcity of available analytical data from a particular artist or physical access for its acquisition is restricted. This poses a fundamental problem for the purpose of conservation, restoration or authentication of historical artworks. We address part of this problem by providing a practical method to generate hyperspectral data from readily available RGB imagery of artwork by means of a two-step process using deep neural networks. The particularities of our approach include the generation of learnable colour mixtures and reflectances from a reduced collection of prior data for the mapping and reconstruction of hyperspectral features on new images. Further analysis and correction of the prediction are achieved by a second network that reduces the error by producing results akin to those obtained by a hyperspectral camera. Our method has been used to study a collection of paintings by Amadeo de Souza-Cardoso where successful results were obtained. CCS CONCEPTS • Computing methodologies → Neural networks; Artificial intelligence; • Applied computing → Arts and humanities.info:eu-repo/semantics/publishedVersio

Biodeterioration of glass-based historical building materials: An overview of the heritage literature from the 21st century

The main goal of this work was to review the 21st century literature (2000 to 2021) re-garding the biological colonisation and biodeterioration of glass-based historical building materials, particularly stained glass and glazed tiles. One of the main objectives of this work was to list and systematize the glass-colonising microorganisms identified on stained glass and glazed tiles. Biodiversity data indicate that fungi and bacteria are the main colonisers of stained-glass windows. Glazed tiles are mainly colonised by microalgae and cyanobacteria. Several studies have identified microorganisms on stained glass, but fewer studies have been published concerning glazed tiles. The analysis of colonised samples is a vital mechanism to understand biodeterioration, particularly for identifying the colonising organisms and deterioration patterns on real samples. However, the complexity of the analysis of materials with high biodiversity makes it very hard to determine which microorganism is responsible for the biodeteriogenic action. The authors compared deterioration patterns described in case studies with laboratory-based colonisation experiments, showing that many deterioration patterns and corrosion products are similar. A working group should develop guidelines or standards for laboratory experiments on fungi, bacteria, cyanobacteria, and algae on stained glass and glazed tiles

Highly conductive p-type nanocrystalline silicon films deposited by RF-PECVD using silane and trimethylboron mixtures at high pressure

In this paper we present a study of boron-doped nc-Si:H films prepared by PECVD at high depositionpressure (>4 mbar), high plasma power and low substrate temperature (7 (U cm)1) andhigh optical band gap (>1.7 eV). Modeling of ellipsometry spectra reveals that the film growth mechanismshould proceed through a sub-surface layer mechanism that leads to silicon crystallization.The obtained films are very good candidates for application in amorphous and nanocrystalline siliconsolar cells as a p-type window layer.Peer reviewe

A transparent dialogue between iconography and chemical characterisation: a set of foreign stained glasses in Portugal

This work presents the first results of the iconographic study and analytical characterisation of a set of four stained-glass panels that are part of the collection of National Palace of Pena (Sintra, Portugal). These panels were collected by the King Ferdinand II in the mid-nineteenth century, for his main residence the Palace of Necessidades (Lisbon, Portugal), and only first presented to the general public in 2011. This study contributes with the knowledge of Technical Art History and Heritage Science to a better and deeper understanding of their history, materials and techniques used in the production, where an art-historical and a scientific approach are applied to attribute their origins. Based on the analysis of the formal and stylistic characteristic of the panels, it is proposed that the drawings used for the production of three of these panels may be based on the design and painting being carried out in the same workshop, and that the four panels have the same provenance (Germany). The composition of the glass and grisaille was determined and colourising elements were identified. Through this approach, conclusive correlation between the analysed glasses was possible: all are calcium rich or calcium–potassium rich types, and the results also suggest that the same source of silica was used for their production. A typical mixture of glass and lead oxide was found in the grisaille applied on the painted panels. However, less usual was the use of a copper oxide pigment for the black grisaille. All these findings support the proposals made regarding provenance and production period (fifteenth century)

Influence of environment on the corrosion of glass–metal connections

'Glass sensors' of the eighteenth century Backer glass and the sixteenth century enamel from Limoges have been chosen for a series of experiments. Combinations of these materials with different base materials such as copper and bronze has been investigated. To create surface changes on the 'glass sensor', a corrosion process was induced in a controlled environment. A variety of corrosive agents such as hydrochloric acid, sulfuric acid, water and formaldehyde were used. The sample immersed in the corrosive solution was exposed alternately to light and high temperature for a total of 38 weeks. During this period, macroscopic and microscopic observations were made and series of tests such as SEM/EDS and Raman spectroscopy were performed on the surface of the samples. ICP-MS methods were used to determine the change in the chemical composition of the solutions where the samples had corroded. The primary aim of this study was to identify the impact of a number of external corrosive variables such as temperature, humidity and local environment to identify the most damaging environments for glass–metal objects. The obtained results showed the chemical and physical phenomena acting on the surface of the glass, metal or in the place of their joints. Information obtained on this study was used to explain the influence of the environment on the surface of glass–metal materials. Results can be used in the design of conservation work as well as for sustainable conservation

Historic K-rich silicate glass surface alteration: behaviour of high-silica content matrices

Several K-Ca-Si glass compositions typical of Central-European glassworks are susceptible to damage beyond recall, even in mild museum conservative conditions. In order to provide a comprehensive picture of the deterioration process, replica samples were produced and exposed to four different museum-like environments. The corrosion experiment was followed by the use of ToF-SIMS, μ-Raman and μ-FTIR, performing a systematic compositional and structural study for the early stages (one year) of surface alteration. This work demonstrates the dominant role of Pb2+ and Ca2+ content for the inferable existence of connected conduction pathways, with strong implications on the surface's hydration, alkali-diffusion and hydrolysis

Materials, Furnaces, and Texts: How to Write About Making Glass Colours in the Seventeenth Century

grant agreement no. 648718 UIDB/00729/2020Johann Kunckel's Ars Vitraria Experimentalis (1679) is arguably the most important text on seventeenth-century glassmaking. As an augmented German translation of Italian (1612) and English (1662) editions, Kunckel presented a complex and layered text that contained a plethora of recipes, elaborate commentaries and annotations, and various appendices dealing with glass-related technologies and arts. We reworked four recipes for rosichiero glass (a transparent red glass) in Kunckel's book to discover what strategies Kunckel employed to help readers engage with the recipes and to make the recipes work in the specificity of their own workshop. We learned that Kunckel regularly neglected to test the Italian recipes, and that not all of his corrections are improvements, thereby specifying our understanding of the “codification of error” as a strategy to write down colour-making knowledge. Instead, Kunckel made the choice to educate his readers on the very mechanisms of glass colouring to allow them to intervene to influence the colour of the glass and to gain further control over the making process. He argued that the colour of glass is sensitive to the manner in which ingredients are sourced and processed, and emphasised the importance of furnace management in optimising the colour of glass.publishersversionpublishe

Characterization and contemporary replicae of Art Noveau coloured glass

Currently the importance of the application of non-invasive and portable techniques to the characterization of glass is well known. However, despite the large number of publications on medieval glass, few studies have been performed on early modern glass. Since the opportunities to sample or to move the work of art out of the conservation location are very limited, the application of non invasive and portable techniques appears to be the best way to perform an in-depth characterization of the chromophores and raw materials even though the complexity of interpreting the results and the lack of references necessitate a preliminary phase of testing on standard and reference samples. In this study a collection of colored and opalescent glasses from the first half of the 20th century and some standard samples of cobalt and cadmium glasses produced ad hoc at the Vicarte Centre (Universidade Nova de Lisboa) were analyzed using both traditional (XRF, SEM-EDS, XRD and UV-Vis-NIR) and portable and non-invasive techniques (XRF, FORS). The standard samples consist of 21 glasses different base compositions (soda-lime, potash and mixed alkali) and different amounts of chromophores. For cobalt colored glasses different amounts of cobalt (0.5, 0.75 and 1% wt) were added to each base composition (9 samples). Also, yellow to orange and ruby red colorations were obtained by modulating the cadmium/sulfide and cadmium/selenium ratios. The cobalt blue glass absorption spectra detected by FORS are usually characterized by three sub-peaks located around 530 nm, 590 nm and 650 nm due to the cobalt tetrahedral coordination. A change in the base composition of the glass could, however, affect the three-peak position due to a change in the ligand field strength. The influence on the FORS spectra of a different base composition and amount of soda present in the glasses (detected by SEM-EDS and XRF) was studied. For glasses with soda content under 15% (some soda-lime samples and mixed base glasses), the resolution of the three-peak absorption band of cobalt is poor. The band appears to be broad, unsymmetrical, and centered around 550 nm even though the characteristic triplet was detected when the amount of soda increased to between 15% and 29%. A shift of about 10 nm in the position of the peaks can be observed in all glasses with a potash base. The study of the glasses colored by CdS and Se is still in progress, and the results will be available soon