During the post-press heating step at 950 C, the TiO2 and SrCl2 create in-filling micro-reactions around each grain resulting in dense (96%) SrTiO3 ceramics. Nano- and micron-sized starting powders were used, demonstrating that this reactive intermediate phase cold sintering route can densify a wide range of starting powder sizes, as it not reliant on an amorphous-to-crystalline precipitation through the terrace ledge kink mechanism, as has been identified repeatedly in previous cold sintering mechanisms.