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.

The Cathedral of León has one of the most important ensembles of medieval stained glass windows in Europe; however, most of them have been altered by atmospheric weathering. The main objective of this study was the characterization of a set of glass samples from the Cathedral of León, the comparison with glasses from previous interventions in the cathedral and the study of the relation between the alteration pathologies, the chemical composition of the glasses and the environment in which they were placed. The samples were characterized by means of binocular microscopy, scanning electron microscopy and energy dispersive X-ray spectrometry, visible spectrophotometry, X-ray fluorescence spectrometry and X-ray diffraction. The main alteration of glasses exposed until the 19th century was the formation of pits by dealkalinization, while the glasses exposed until the present formed CaSO4 deposits as a consequence of the synergic effect of rainwater and gaseous pollutants. Glasses altered by the browning of manganese were also characterized. Resumen La Catedral de León posee una de las colecciones de vidrieras medievales más importantes de Europa; sin embargo, muchos de los vidrios se han alterado por degradación atmosférica. El objetivo principal de este estudio fue la caracterización de un conjunto de vidrios procedentes de la Catedral de León, su comparación con vidrios procedentes de intervenciones previas en la catedral y el estudio de la relación entre las patologías de alteración, la composición química del vidrio y el medio en el que estuvieron expuestas. Las muestras se caracterizaron mediante lupa binocular, microscopía electrónica de barrido y microanálisis de dispersión de energía de rayos X, espectrofotometría visible, espectrometría de fluorescencia de rayos X y difracción de rayos X. La alteración principal de los vidrios expuestos hasta el s. xix consistió en la formación de picaduras por desalcalinización, mientras que en los vidrios expuestos hasta la actualidad se formaron depósitos de CaSO4 como consecuencia del efecto sinérgico de la lluvia y los gases contaminantes. También se han caracterizado vidrios alterados por el enmarronamiento del manganeso.

The aim of this work was to determine the physico-chemical characteristics of the stained-glass windows into the 19th century of two mausoleums located in the city of Belém do Pará (Brazil), and to evaluate their state of conservation. The glass chemical composition was determined by WXRF and SEM/EDS. The samples’ morphology and the microorganisms’ identification were carried out by optical microscopy. The results indicated that the samples were soda-lime silicate glass, with approximately 70wt. % of SiO2, which contributed to the resistance of the stained glass to the weathering. The concentration of Na2O was normally twice the K2O, which contrasts with the composition of other panels produced during the same period, as reported in the literature. The biofilm is composed by cyanobacteria and rotifers. Overall, the panels analysed were in a good state of conservation, despite their exposure to tropical climate conditions for more than a century with no preventive measures whatsoever. Resumen El objetivo del presente trabajo fue determinar las características físico-químicas de las vidrieras del siglo XIX correspondientes a dos mausoleos ubicados en la ciudad de Belém do Pará (Brasil) para evaluar su estado de conservación. La composición química del vidrio fue determinada por WXRF y SEM/EDS. La morfología de las muestras y la identificación de los microorganismos fueron realizadas por microscopia óptica. Los resultados indicaron que las muestras eran vidrios de silicato sódico-cálcico, con aproximadamente el 70% en peso de SiO2, lo que aumentó la resistencia a la corrosión de los vidrios de estas vidrieras. La concentración de Na2O fue normalmente el doble que de K2O, lo que contrasta con la composición de otros paneles producidos durante el mismo período, de acuerdo con la literatura. El biofilm presentó cianobacterias y rotíferas. En general, los paneles analizados presentaban un buen estado de conservación, a pesar de su exposición a las condiciones climáticas tropicales durante más de un siglo, sin las medidas de conservación preventivas.