The technology of copper-based red glass sectilia from the 2nd century ad lucius verus villa in rome

PD/BD/135053/2017This work aimed to investigate the origin of different red hues of Roman copper-based red opaque glass sectilia, to shed light on the production technology behind them. This objective was achieved by the depth study of the samples of glass sectilia, which decorated the villa of co-Emperor Lucius Verus (161–169 AD). These were selected for analysis due to their abundance, the certainty of their date and of their different red and orange hues. Using OM (optical microscopy), colourimetry and FORS (fibre optical reflectance spectroscopy) spectroscopy, four red and four orange hues were individuated. A set of representative samples for each hue was analysed by EPMA (electron probe microanalyses) to detect any correlation between colour and chemical composition. Crystalline phases were investigated through high-resolution FEG–SEM (field emission gun scanning electron microscope), µRaman spectroscopy and XRD, for the identification of colouring and opacifying agents and to understand how the different hues are affected by their shape, concentration and dimension. Sub-micrometric particles of metallic copper and cuprite crystals were identified as both the colouring and opacifying agents. These were not present in the same samples and were manufactured by two distinct colouring techniques, corresponding to two different glass chemical compositions. The size and the number of the colouring particles were the main factors that distinguished one hue from another. Although produced through different colouring techniques, some red samples appeared to be very similar to each other. These data enrich a period of the Roman age through some analyses and allow the identification of the type, as well as some of the production conditions of opaque red glass produced during 2nd century AD, which could be considered to be a period of transition from one technology to another.publishersversionpublishe

uma revisão bibliográfica

Conservation and restoration on archaeological objects in glass often involve the removal of materials from previous restorations and comprise a deep knowledge about present and past methodologies. This article presents a literature survey and critical analysis of the main materials used in the different stages of intervention: cleaning, consolidation, joining fragments and filling gaps. A considerable number of used products was identified, which illustrates the use of various methodologies among professionals from this area. Cleaning methods vary from mechanical methods using a brush (less invasive) to the use of various acidic solutions, some of which can endanger the integrity of objects, being the most common ethylenediamine tetra-acetic acid. We highlight the use of epoxy resins as adhesive, consolidant and filler, as well as the acrylic resin Paraloid B72, identified as reversible, colorless, stable and inert. This survey and analysis of the bibliography reveals the need to implement common intervention methodologies dedicated to this material.publishersversionpublishe

Impact of solar radiation and environmental temperature on Art Nouveau glass windows

Fundacao para a Ciencia e Tecnologia of Portugal (Project Ref. UID/EAT/00729/2019). Fundacion General CSIC of Spain (ComFuturo Programme). We also acknowledge support of the publication fee by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI).This work presents the results of the evaluation of two Art Nouveau glass windows from the Casa-Museu Dr. Anastácio Gonçalves (Lisbon, Portugal) with IR-thermography during the summer solstice. According to the measurements, the surface temperature of glass depended on the outdoor environmental temperature and, mainly, on the direct solar radiation. Colored glasses presented a higher surface temperature due to the absorption of their chromophores at near-IR wavelengths. Enamels and grisailles showed higher surface temperatures than their support glasses due to both their chemical composition and color. The protective glazing, with small slits in one of the window panels, induced a hot-air pocket in its upper part due to the insufficient ventilation.[Figure not available: see fulltext.]publishersversionpublishe

Characterization of the Alteration of Debitus Grisailles

Stained glass restoration generally involves filling glass losses to maintain the coherence of the window and the new glasses used to fill the losses can be painted to chromatically reintegrate the stained glass panel. One of the most common painting materials on stained glass is grisaille, a paint made by mixing metal oxides with a ground lead glass. Grisailles usually have black and brown hues and are used for the creation of outlines as shadows in window glasses. Although several commercial companies sell many types of products to paint on glass, few of them present the necessary compatibility with the original materials that conservation materials must have. Debitus is one of the most renowned companies, and its grisailles are frequently used for chromatic reintegration in stained glass window restoration. Thus, the main objective of this study was to assess the long-term stability and durability of commercial Debitus grisailles. Two alteration tests were carried out, with samples placed in high humidity chambers and submerged in distilled water. The samples and degradation products were characterized by optical microscopy, µ-Raman spectroscopy, and colourimetry. In the immersion, the pH of the water was measured during the experiment, and the leached elements were analyzed at the end by inductively coupled plasma atomic emission spectroscopy. The results showed an alteration of the colour and the formation of degradation products, identified as sulphates. The solution pH was increased by the aqueous extraction of alkaline and alkaline-earth ions from the support glass of the samples. Despite these changes, it was possible to conclude that these commercial grisailles presented good durability and stability for use in conservation treatments.This work was supported by Fundação para a Ciência e a Tecnologia (Portugal) [Grant Number UID/EAT/00729/2020 andPD/BD/136673/2018]; Fundación General CSIC (Spain)[Grant Number ComFuturo Programme]

Assessing the decorative techniques of two Art Nouveau glass windows by optical coherence tomography (OCT)

Abstract This work presents an assessment of the different decoration techniques applied in the two glass windows from the Casa-Museu Dr. Anastácio Gonçalves (Lisbon, Portugal) by Optical coherence tomography (OCT). The Dining Room glass window was found to be decorated with grisailles and acid etching, and the Atelier window with grisaille, enamel, and cold painting. The alteration state of the surface decorations was also assessed. The thicker surface decorations (grisailles and enamels) presented cracks and detachments, in contrast to the thinner lines which are normally well preserved. OCT is a suitable technique for characterizing glass decoration in situ without dismounting the stained-glass window; and able to reveal the condition and methods of manufacture that cannot be detected simply by visual inspection

The Influence of Environment in the Alteration of the Stained-Glass Windows in Portuguese Monuments

This work presents the results of the exposure of soda-lime, potash-lime and mixed-alkali silicate glasses during ten and twenty months in different Portuguese monuments with historical stained-glass windows to characterize the influence of local environmental conditions. The glass samples were exposed in the Monastery of Batalha (Batalha), the Monastery of Jerónimos (Lisbon), and the Cathedral of Évora (Évora). A set of analytical techniques to assess the physicochemical effects were used, including optical microscopy and Fourier transform infrared spectroscopy. All the samples presented crystalline deposits on their surface; however, their quantity and nature depended on the atmospheric conditions during the days before the collection. Potash-lime silicate glass was the most altered glass in comparison with soda-lime and mixed-alkali silicate glasses. The samples from the Cathedral of Évora showed a high content of dust and salts on their surface but without severe chemical pathologies; however, those samples exposed in the Monastery of Jerónimos and the Monastery of Batalha presented alteration layers due to a high humidity environment

Analysis of chromophores in stained-glass windows using Visible Hyperspectral Imaging in-situ

This work presents the implementation of Visible Hyperspectral Imaging for the in-situ analysis of glass chromophores in two glass windows from the Casa-Museu Dr. Anastácio Gonçalves (Lisbon, Portugal). The measurements were taken inside the building using natural sunlight as the illumination source. In addition, advantages and disadvantages of the followed methodology are discussed. The Dining Room glass window presents glasses colored in bulk with iron, manganese, cobalt, copper, and chromium; silver staining was also detected and was used to create the yellow and orange colors. The Atelier panel was produced with uncolored glasses painted with grisaille and enamels; the chromophores identified are similar to the species identified in the Dining Room panel.The authors thank Dr. T. Marques and Dr. A. Mântua (Casa-Museu Dr. Anastácio Gonçalves, Lisbon, Portugal) for the facilities provided to accomplish this research and B. Doherty (SMAArt Centre and CNR-ISTM, Perugia, Italy) for the manuscript revision. This work has been funded collectively by the Access to Research Infrastructures activity in the Horizon 2020 Programme of the EU (IPERION CH Grant Agreement n. 654028), the Fundação para a Ciência e a Tecnologia de Portugal (Project ref. UID/EAT/00729/2019) and Fundación General CSIC (ComFuturo Programme).Peer Reviewe

Estimating the colors of paintings

Observers can adjust the spectrum of illumination on paintings for optimal viewing experience. But can they adjust the colors of paintings for the best visual impression? In an experiment carried out on a calibrated color moni- tor images of four abstract paintings obtained from hyperspectral data were shown to observers that were unfamiliar with the paintings. The color volume of the images could be manipulated by rotating the volume around the axis through the average (a*, b*) point for each painting in CIELAB color space. The task of the observers was to adjust the angle of rotation to produce the best subjective impression from the paintings. It was found that the distribution of angles selected for data pooled across paintings and observers could be de- scribed by a Gaussian function centered at 10o, i.e. very close to the original colors of the paintings. This result suggest that painters are able to predict well what compositions of colors observers prefer.This work was supported by the Centro de Física of Minho University, by FEDER through the COMPETE Program and by the Portuguese Foundation for Science and Technology (FCT) in the framework of the projects PTDC/MHC-PCN/4731/2012 and PTDC/EAT- EAT/113612/2009, by and the COST-Action TD1201, Colour and Space in Cultural Heritage (COSCH) through Short Term Scientific Missions (STSM): “Hyperspectral imaging on historical manuscripts and natural scenes” (COST-STSM-TD1201- 010813-032699, 2013). Cristina Mon- tagner was supported by the grant SFRH/BD/66488/2009

Hydrogen plasma treatment of very thin p-type nanocrystalline Si films grown by RF-PECVD in the presence of B(CH3)3

We have characterized the structure and electrical properties of p-type nanocrystalline silicon films prepared by radio-frequency plasma-enhanced chemical vapor deposition and explored optimization methods of such layers for potential applications in thin-film solar cells. Particular attention was paid to the characterization of very thin (~20 nm) films. The cross-sectional morphology of the layers was studied by fitting the ellipsometry spectra using a multilayer model. The results suggest that the crystallization process in a high-pressure growth regime is mostly realized through a subsurface mechanism in the absence of the incubation layer at the substrate-film interface. Hydrogen plasma treatment of a 22-nm-thick film improved its electrical properties (conductivity increased more than ten times) owing to hydrogen insertion and Si structure rearrangements throughout the entire thickness of the film