Sintering experiments on soda-lime glass microspheres have been performed using spark plasma sintering in the temperature range 485 degrees C-560 degrees C. Samples with relative densities between 64% and 99.6% have been obtained in about 10 min. For almost fully dense samples, the microstructure exhibits an unusual "interface-like" aspect for a glass. The densification mechanism has been investigated. For temperatures below 522 inverted perpendicular C, densification proceeds by formation of necks between spheres. For temperatures of and above 522 degrees C, it is proposed that densification proceeds by viscous flow, accommodated by plastic deformation of microspheres, and is controlled by diffusion of oxygen anions in the glass.