19th century stained-glass windows from Belém do Pará (Brazil): Analytical characterisation and pathology

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 Belem do Para (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 70 wt. % of SiO 2 , which contributed to the resistance of the stained glass to the weathering. The concentration of Na 2 O was normally twice the K 2 O, 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.