Chemical fertilizers, such as potash, have a strong tendency to cake when exposed to humidity. In this work, a novel synchrotron-based X-ray tomography 3D-imaging technique was for the first time employed to investigate the solid bridge formation from 2D and 3D perspectives. Image processing and a theoretical model were presented to demonstrate recrystallization near contact points between potash particles during a conventional drying process. The effect of initial moisture content on the water activity of surface surrounding the contact points was investigated. The results showed that by increasing the moisture content of particles (3%–5%), the dissolution of sylvite increased and the solid bridge length between potash particles was enlarged from 28 μm to 44 μm due to supersaturation conditions. In addition, the external porosity of potash particles at the end of drying process decreased from 25.3% to 19.5% for 3% and 5% moisture content, respectively.