The crystallization processes that occur in alkaline earth silicate glasses designed for sealing solid oxide fuel cells (SOFC) have been investigated using differential thermal analysis (DTA) and hot-stage microscopy (HSM). HSM experiments revealed that glass powders with particle sizes < 45 μm crystallized before viscous sintering was complete. This behavior is consistent with the effects of glass particle size on the characteristic temperatures measured by DTA. The importance and role of the specific crystallization process on the effectiveness of glasses for SOFC sealing applications are discussed. © 2010 Elsevier B.V. All rights reserved.