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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]

Flashed glasses are composed of a base glass and a thin colored layer and have been used since medieval times in stained glass windows. Their study can be challenging because of their complex composition and multilayer structure. In the present work, a set of optical and spectroscopic techniques have been used for the characterization of a representative set of flashed glasses commonly used in the manufacture of stained glass windows. The structural and chemical composition of the pieces were investigated by optical microscopy, field emission scanning electron microscopy-energy dispersive X-ray spectrometry (FESEM-EDS), UV-Vis-IR spectroscopy, laser-induced breakdown spectroscopy (LIBS), and laser-induced fluorescence (LIF). Optical microscopy and FESEM-EDS allowed the determination of the thicknesses of the colored layers, while LIBS, EDS, UV-Vis-IR, and LIF spectroscopies served for elemental, molecular, and chromophores characterization of the base glasses and colored layers. Results obtained using the micro-invasive LIBS technique were compared with those retrieved by the cross-sectional technique FESEM-EDS, which requires sample taking, and showed significant consistency and agreement. In addition, LIBS results revealed the presence of additional elements in the composition of flashed glasses that could not be detected by FESEM-EDS. The combination of UV-Vis-IR and LIF results allowed precise chemical identification of chromophores responsible for the flashed glass coloration. [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]