Abstract: Waste substance such as incineration ash is mixed with cullet and alkaline earth salt to form a mixed batch which is added to a glass melt heated solely by electrodes, producing an exhaust gas which is introduced into the batch thereby cooling the gas to produce condensation products. The alkaline earth salt reacts with alkali in the gas and the condensation products to produce a gall layer of alkali salts and alkaline earth salts which serve as a melt accelerator and are readily removed when accumulated. According to a further step the gas is purified by separating dust therefrom and introducing it into the batch as a slurry.