The viscous sinteringSinteringviscous sintering" \r "viscousinteringViscous sintering" \r "viscousintering of glass and amorphous particles occurs through viscous flow driven by surface tension and applied pressure. The complex microstructural evolution is predicted by solving the Stokes equation under specific boundary conditions. In contrast to the solid-state sintering of crystalline particles, the velocity field in a viscous fluid is represented by streamlines. The neck growth rate and shrinkage rate are driven by the sintering force at the contact in computer simulations of the viscous sintering of two particles. The continuum theory of viscous sintering at the macro scale is developed based on sintering stress and demonstrates agreement with classical theories, namely the Mackenzie-Shuttleworth model and the Scherrer model.