Solid oxide electrolysis cell (SOEC) stack obtainable by a process comprising the use of a glass sealant with composition 50 to 70 wt % SiO2, 0 to 20 wt % Al2O3, 10 to 50 wt % CaO, 0 to 10 wt % MgO, 0 to 2 wt % (Na2o 1K2O), 0 to 10 wt % b2O3, and 0 to 5 wt % of functional elements selected from TiO2, ZrO2, ZrO2, F, P2O5, Mo03, FeO3, MnO 2, La—Sr—Mn—O perovskite (LSM) and combinations thereof. Preferably, the sealant is a sheet of E-glass fibers with a composition in wt % of 52-56 SiO2, 12-16AL2O3, 16-25 CaO, 0-6MgO, 0-2 Na2+K2O, 0-10 B2O3, 0-1.5 TiO2, O-1F.