Glass compositions have been formulated and tested for use as viscous seals for solid oxide fuel cells (SOFCs). These alkali-free borosilicate glasses possess desirable thermomechanical properties and thermo-chemical characteristics, and exhibit promising hermetic sealing and self-healing behavior under SOFC operational conditions. The dilatometric softening points (Ts) and the glass transition temperatures (Tg) of the glasses are generally under 650°C, the lower bound of the SOFC operating temperature. To date, glass seals between a YSZ-NiO/YSZ bilayer and aluminized stainless steel 441 have survived 100 thermal cycles (750°C to room temperature) in dry air at a differential pressure of 0.5 psi (26 torr) over the course of > 3,300 hours without failure, and 103 thermal cycles under wet forming gas. Seals intentionally cracked upon quenching from 800°C to RT at >25°C/s become hermetic upon reheating to 700°C and higher.