This study evaluated the mechanical reliability of glass seal in planar type solid oxide fuel cells and clarified the relationship between glass wettability and the mechanical reliability of glass seal. A visualization experiment was developed to observe a specific model seal in a furnace subjected to temperature variation and the relationship between the glass wettability and the seal shape was measured. The seal model consists of glass (G018-311, Schott, Germany) and interconnectors (Crofer 22 APU, VDM Metals GmbH, Germany). The visualization experiment and analysis were based on the sessile drop method to quantify glass surface tension and contact angle between glass and interconnector. The equation balance of forces with these surface properties succeeded to reproduce the seal shape observed in the visualization. Subsequently, the seal stress field was numerically solved, and the mechanical strength of the seal was quantitatively evaluated using the stress intensity factor. The analyses concluded that the stress intensity factor is 1.5 times higher than its minimum value as the contact angle raised from 90 to 130 degrees and glass wettability decreased. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.