This paper discusses experimental determination of solid oxide fuel cell (SOFC) glass-ceramic seal material properties and seal/interconnect interfacial properties to support development and optimization of SOFC designs through modeling. Material property experiments such as dynamic resonance, dilatometry, flexure, creep, tensile, and shear tests were performed on PNNL's glass-ceramic sealant material, designated as G18, to obtain property data essential to constitutive and numerical model development. Characterization methods for the physical, mechanical, and interfacial properties of the sealing material, results, and their application to the constitutive implementation in SOFC stack modeling are described. Published by Elsevier B.V.