Optimizing the process of ceramics stereolithography (CSL) necessitates the thorough understanding of the complex interactions between light and ceramic particles. This contribution provides an insight into the influence of particle size distribution on the rheological behavior and the polymerization kinetics of photo-curable ceramic resins. Four grades of α-Al2O3 with different particle size distributions were investigated, and an acrylate-based photo-curable resin was used. The particle size distribution was measured using a laser diffraction particle size analyzer based on the Mie theory. The quantum of scattered and absorbed light was measured with a UV/Vis spectrophotometer, equipped with a modified integrating sphere accessory. The use of the modified integrating sphere allowed us to separate scattered, absorbed and transmitted light, and measure each. UV/Vis measurements revealed that samples with a smaller mean particle size result in a higher absorbance and a lower scattering in the wavelength range of 190 nm to 420 nm. Moreover, photo-rheology measurements revealed that larger particles generally result in faster polymerization rates without a noticeable change in the conversion levels for the same solids content. Contrary to common misperception, it was found that scattering by the particles is not the main factor resulting in a reduction in the polymerization rate. Higher absorbance by the particles, on the other hand, results in a direct reduction in the polymerization rate. In addition, sedimentation tests revealed that ceramic resins with a larger mean particle size exhibit a lower viscosity and a lower sedimentation stability compared to those with a smaller mean particle size. The findings of this work support the process of selecting ceramic powders and preparing ceramic resins for stereolithography. An optimized selection process results in an increase in the sedimentation stability of the ceramic resin, and a customization of its curing behavior.