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The most frequent cause of glass degradation is environmental moisture, which is adsorbed on its surface forming a hydration layer that induces the rupture of the glass network. This pathology is accelerated by the accumulation of volatile organic compounds (VOCs), like formic acid. Although there is extensive knowledge about their impact, concentrations inside display cases are difficult to reduce efficiently. This study presents the assessment of different materials to reduce the concentration of formic acid to mitigate the degradation produced in unstable glasses. With this objective, copper threads, steel wool, silica gel, and activated carbon were chosen as low-cost materials with good adsorption or reactivity to the VOCs, exposing them in desiccators to an environment of 100% RH and 10 ppm of formic acid. Given that silica gel obtained the best results, its optimization as a sorbent material was evaluated by maintaining, regenerating, or renewing it when exposed next to the same glass. The tests carried out concluded that the hygroscopic capacity of the glasses exposed with silica gel decreased and, therefore, a lower degradation is observed on its surface. In addition, regenerating and renewing weekly the silica gel improved the results. [ABSTRACT FROM AUTHOR]

The present work aims to study the glasses commonly named crystal glass produced in Portuguese factories from the 18th to the 20th centuries through their arcana or batch books. Recipes for colorless crystal glasses were selected, analyzed, and reproduced in the laboratory. Five recipes were chosen from the Marinha Grande arcanum, five recipes from the Gaivotas' Factory arcanum, and three recipes from the Castro and Oliveira Guerra arcanum. To characterize the composition and thermal‐physical properties of reproduced glasses, different analytical techniques were used such as micro‐energy dispersive X‐ray fluorescence, µ‐ Raman spectroscopy, differential scanning calorimetry, dilatometry, Vickers hardness, optical microscopy, and UV‐Vis absorbance spectroscopy. The selected recipes were proven viable for reproduction and the obtained glasses presented good thermal properties that allow the workability and creation of objects. It was also proven that there is a similarity in terms of chemical composition to some of the historical glasses attributed to Portuguese production in Portuguese museums. [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]

Abstract: This paper reports the analyses of infrared thermography images of two stained‐glass windows with the objective of the in situ characterization of this type of artworks. The analyses were carried out by active thermography. The observations revealed that glasses absorbed the long‐wave IR radiation emitted by the halogen lamps and their apparent surface temperature progressively increased. After switching the spotlight off, they experienced a progressive decrease in temperature. Silver stained glasses presented the same thermographic behavior than uncolored glasses because silver nanoparticles were too small or the yellow layer was too thin to produce a different response than the base glass with the IR radiation. The apparent surface temperature of enamels and grisailles depended on their thickness and color. Lead cames maintained an almost constant surface apparent temperature, except those painted that behave in a similar way than enamels. Metallic tin‐lead welds experienced the most important variation in the surface apparent temperature in reflection mode due to the energy reflected by the surface of the weld. Glass defects such as big bubbles were also observed. [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 reports the research on the physical-chemical response of silicate glasses subjected to the action of three natural soils types: acidic, neutral, and basic. The main goal of the study was to characterize the corrosion mechanisms acting upon glasses formulated with chemical compositions that are commonly found in historical glasses through an accelerated aging test that replicates natural burial. Resulting data showed a distinct and recognizable response of each glass type, with pH as the key variable for glass corrosion. Results can be of great significance to historical glass studies, especially in choosing suitable conservation strategies for archeological findings. [ABSTRACT FROM AUTHOR]

• The complete study of thermal behavior of colored glasses have been done. • It has proved the relationship between the chromophores and the thermal behavior on colored glasses. • Bluish glasses have the highest NIR absorption, thermal conductivity, thermal expansion coefficient and the largest heating curve. Solar irradiation can induce different process on glasses. In this study, the thermal behavior of colored glasses (colorless, red, yellow, green, turquoise, blue, purple, and brown) were characterized by UV-vis-IR spectrophotometry, thermal conductivity-meter, infrared thermocamera and dilatometry. The calculation of the absorption coefficients and the thermal conductivity showed that the heating of each fragment depends predominantly on the chromophores. Blue, green and turquoise glasses present the highest NIR absorption, thermal conductivity, thermal expansion coefficient and the largest heating curve. In comparison with colorless glass, the expansion coefficient of bluish glasses is > 5·10−7°C−1 that can produce a thermal incompatibility with the formation of fissures and detachments. [ABSTRACT FROM AUTHOR]

Glass mosaic decorations were used throughout the medieval Mediterranean as a powerful medium to convey religious and political agendas, yet we know next to nothing about the source of the materials and the transmission of the necessary technical know-how. Mosaics are generally considered a Byzantine art form, not least due to their prominence in Byzantine church architecture and because medieval Islamic textual sources assert that the glass tesserae of some of the most important early mosques were of Byzantine origin. This article provides solid analytical evidence that glass used in the tenth-century mosaics of the Great Umayyad Mosque of Córdoba (Spain) came from Byzantium. Most of the tesserae have high boron contents, for which the only compositional match are Byzantine glasses made with raw materials from Asia Minor. In addition, some of the glass has a chemical fingerprint that suggests that it was prepared by mixing local raw materials with imported high boron glass, indicative of local mosaic glassmaking. Our study thus illustrates the value of analytical studies in re-assessing long-held assumptions about the making of mosaics as well as the movement of materials and people across cultural barriers. The presence of Byzantine materials and craftsmen in Córdoba demonstrates that Muslims and Christians were interacting the length of the Mediterranean, corroborating the close diplomatic ties between the Caliphate of Córdoba and the Byzantine Empire during the tenth century. Our findings further underscore the importance of glass in trade and diplomatic exchange, reflecting its cultural and economic value in the medieval world. • Glass tesserae from the Great Umayyad Mosque of Cordoba imported from Asia Minor. • Highest number of high boron glass outside the Byzantine Empire and furthest west. • Mixed lead/boron compositions indicate local secondary production of some tesserae. • Technological transfer between the Byzantine Empire and Islamic Caliphate of Cordoba. [ABSTRACT FROM AUTHOR]

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. [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]