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The control of humidity between certain limits is essential to avoid the alteration of historical objects, such as unstable historical glasses. However, the usual limits can be altered due to the presence of volatile organic compounds. This work presents the results of the exposure of soda, potash, and mixed‐alkali silicate glasses to neutral and acidic (formic) atmospheres with ∼30%, ∼70%, and ∼100% relative humidity. The hygroscopic capacity of the glass was analyzed by gravimetry, and the surface alteration was evaluated by infrared spectroscopy, optical microscopy, and ion chromatography. In all glasses, the alteration begins with alkali ions' lixiviation followed by the silica network's hydrolytic attack. The results showed that soda and mixed‐alkali silicate glasses exhibit similar behavior, while the potash‐lime one experienced the fastest degradation due to its composition. Results also confirmed that high humidity increased the alteration rate causing a higher hygroscopicity and reactivity of glasses. Finally, acidic environments promoted the ion‐exchange reaction at high humidity, accelerating the lixiviation of alkaline ions and promoting the diffusion of water into the glass network. [ABSTRACT FROM AUTHOR]

Historic glasses can be altered in the presence of inorganic pollutants, such as CO2, SO2, or NO2, but also, by the volatile organic compounds emitted by the museum cabinets. Among these pollutants, compounds with carbonyl groups such as acetic and formic acids, and formaldehyde are the most common ones. In this work, a study of the interaction of these contaminants with three of the most relevant historical glasses was carried out. These glasses were soda silicate glass, potash silicate glass, and lead crystal glass. Two alteration tests were carried out in these glasses in the presence of water, acetic acid, formic acid, or formaldehyde. In the first test, the alteration induced by the liquid solution was evaluated by the pH monitoring and the study of the ions lixiviated by inductively coupled plasma optical emission spectroscopy. In the second study, the alteration with gaseous contaminants was carried out. The hygroscopic capacity of the glasses was analyzed by gravimetry, the evolution of the glass surface by Fourier transform infrared spectroscopy in attenuated total reflectance mode, and the ions found on the glass surface by ion chromatography. These methods allowed to observe the different degradations that occurred in the three glasses in the presence of different pollutants in aqueous or gaseous environments. [ABSTRACT FROM AUTHOR]

Grisaille is a glass-based paint made by mixing metal oxides (iron or copper) with ground lead-silica glass. The different materials used in the grisailles production (coloring agents, base glasses, or vehicles) can significantly impact their long-term stability along with the firing conditions. The main objective of this study was to achieve a better understanding of how raw materials influence the production and stability of these paints. To achieve this goal, 27 grisailles were produced, changing the raw materials, proportions, and firing conditions. The produced grisailles were characterized by X-ray fluorescence and diffraction, colorimetry, roughness measurement, and contact angle analysis. Adhesion and cleaning tests were also made. The use of different coloring agents has a significant impact on the final appearance and on the chemical and mechanical stability of the grisailles, but the latest is more affected by both firing temperature and the proportion between pigments and base glasses. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Some historical glasses (lead‐wood ash glasses, lead‐crystal glasses...) are silicate glasses with high content of lead and potassium. This work presents the evaluation of the chemical stability of high‐lead glasses in a high relative humidity atmosphere and as result of aqueous immersion. In both situations, the alteration mechanism begins with the lixiviation of alkali metal and lead ions, followed by the hydrolytic attack of the silica glass network. According to the results, the glasses with a higher content of lead show the fastest degradation due to their higher hygroscopicity. Environmental CO2 can be dissolved in the adsorbed water and favor the formation of intermediate degradation compounds. [ABSTRACT FROM AUTHOR]

Abstract Urban and industrial atmospheres can produce several damages on glass façades and historical stained-glass windows; however, the effect of coastal atmosphere on them has been scarcely studied. This work presents the results of the exposure of soda-lime, potash-lime, and mixed-alkali silicate glass to the coastal atmosphere in Cape Vilán (Galicia, Spain) at different distances to the coast (inland) during twelve months. Crystalline deposits were observed on all the samples, although their quantity depended on the meteorological conditions. The samples located nearest to the coast presented alteration layers, while those ones located farthest from the shore presented several isolated pits. Regarding the chemical composition, potash-lime silicate glass, typical composition from medieval glass windows, was the most altered glass in contrast to soda-lime and mixed-alkali silicate glasses. Graphical abstract Image 1 Highlights • The glass alteration depended on the distance to the coast. • The glasses exposed near the coast presented alteration layers on their surface. • The glasses exposed far from the shore presented isolated pits. • Potash-lime silicate glass was the most altered glass. [ABSTRACT FROM AUTHOR]

This work is focused on the effect of marine aerosols on soda-lime, potash-lime and lead silicate glass samples. Two kinds of tests were carried out, the first one under laboratory controlled condition during 36 days to evaluate the alteration of glass surface by NaCl aerosols, and the second one in a marine atmosphere in Cabo Vilano (Galicia, Spain) for up to three months. Both tests showed similar results. NaCl aerosols acted as condensation nuclei in high humidity environments favoring the lixiviation of the alkaline and alkaline-earth ions from the glass surface and the solubilization of atmospheric gases (CO 2 , SO 2 ). Marine aerosols could also accelerate the corrosion attack inducing the loss of the surface hydrogen bonds and the opening of the network accelerating the corrosion mechanism. Results also confirmed that high humidity favored the alteration of the glass surface and the formation of new crystalline phases. Soda-lime silicate and lead silicate glasses were the most durable ones, whereas potash-lime silicate glass presented a fissured alteration layer due to the hydrolytic attack of the surface. New crystalline phases including chlorides, carbonates and sulfates were detected on the glass surfaces which can be related to marine aerosols, environmental particles and the reaction of the cations lixiviated from the glass with the atmospheric gases. [ABSTRACT FROM AUTHOR]

This paper presents the results derived from an archaeometric study undertaken on glass samples from the Roman town of Augusta Emerita (Mérida, Spain). The main goal of the research was to provide for the first time some compositional and technological insights into the glass finds unearthed in this town. Glass samples from different sites and chronology, either from inside or from outside the perimeter of the ancient town and from the first to the sixth century AD, were analyzed and characterized through optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive X-ray microanalysis (EDS), X-ray fluorescence (XRF) spectrometry and VIS spectrophotometry. Resulting data indicated that all the samples studied were natron-based soda lime silicate glasses, even though two chronological and compositionally distinct groups were distinguished. One composed of Early Empire glasses and a second one composed of glasses from the fourth century AD onward, which was characterized by the presence of the so-called HIMT (high iron, manganese, and titanium) glasses. Comparison with coeval glasses suggested that Augusta Emerita shared the same trade glass circles than other contemporary Roman towns, within the frame of a secondary production scale. Finally, some outstanding differences connected to composition and chronology were found, since Late Roman glasses presented a higher and distinct degree of alteration than Early Empire ones. [ABSTRACT FROM AUTHOR]

• K 2 O-PbO-(CaO)-SiO 2 glasses were altered in atmospheres enriched in formic acid. • Higher was the concentration of formic acid, faster was the alteration. • The addition of stabilizers to the glass slowed down the alteration rate. • For the same molar concentration, calcium was better stabilizer than lead. George Ravenscroft designed the lead silicate glasses in 17th-century; however, the first pieces produced showed degradation pathologies after few years. This study reproduces one of the glasses produced by George Ravenscroft and analyses its chemical stability in comparison to two other glasses based on the original composition but with the addition of 5 mol % of PbO and CaO, respectively. The three glasses were exposed to an environment of high humidity and different concentrations of formic acid (0, 100 and 300 ppm), which is the main contaminant in display cases and wooden cabinets. The hygroscopic capacity of the glass was analysed by gravimetry, infrared spectroscopy and µ-Raman spectroscopy. The results show that the acidic environment promotes the ion exchange reaction, accelerating the leaching of alkaline ions, which has a great influence on the durability of the glass. The glasses with a higher content of stabilizers presented a greater stability, especially the glass with calcium. [Display omitted] [ABSTRACT FROM AUTHOR]