In a recent report by Guillon and co-workers on the CSP of ZnO with a small amount of water, they argued that the solution-precipitation mechanism proposed by Randall group was not enough to activate the densification process.Due to the diffusion of H+ and OH− ions into the ZnO crystal, a high defect concentration could be produced at the grain boundaries with high potentials. Because of the formed defect sites, a high diffusion path was created, which was beneficial for mass-transport and low-temperature sintering.