Research into hydrogen production using high temperature electrolysis methods has increased significantly in the last few years. Consequently, development of sealing materials has become a major concern particularly for developers of Solid Oxide Electrolyser Cells (SOECs). Suitable sealants for SOECs must operate around 800°C for many hours under reducing and oxidizing conditions. Glass-ceramic compositions based on two glass systems CAS (CaO-Al2O3- SiO2) and SCAS (SrO-CaO-Al2O3-SiO2) with some minor additions (MnO2, B2O3 or TiO2) have been prepared and investigated. Thermal, chemical, and physical properties of the glass ceramics were examined along with the glass crystallization behaviour. Hot Stage Microscopy allowed observation of the sintering and wetting behaviour of glass-ceramics and showed it to be a complex process, significantly affected by glass composition, viscosity, glass transition temperature, crystallization rate and the nature of the crystalline phases formed. The bonding characteristics of parent glasses with ceramic and/or metallic interconnector were observed under air at the cell operating temperature. The results revealed the most suitable glass-ceramic compositions to meet the different criterions and the difficulties involved in formulating such materials.