This paper presents the corrosion of potassic glasses by SO2 gas at high-temperature. The corrosion phenomenon of potassic glass is well-known for medieval stained-glass windows under natural conditions of weathering . Nevertheless the corrosion is also possible without humidity at high temperature in presence of polluting gas such as SO2 gas in the furnace. All source of SO2 gas can thermodynamically involve the main formation of K2SO4 and other alkaline salts such as Na2SO4. This corrosion manifests itself by the presence of “white flakes” in the bulk glass and this defect leads to discard of the piece for a crystal-maker like Daum. Alkali sulphate formation was determined by using scanning electron microscopy and presents a very particular morphology. This study allowed underlining on, one hand the influence of the temperature and on the other hand the role of gas concentration on the formation of the potassium sulphate. Thermal analysis technique (TGA) was carried out in order to understand the corrosion chemical kinetic of potassic glasses by SO2 gas.