This article addresses the microstructure and related mechanical properties of gypsum produced from ß-hemihydrate using information of its hydration process, from fresh paste to hardened gypsum. The water demand of the investigated ß-hemihydrate was determined applying the spread flow test. The flowability was studied and the deformation coefficient of the ß-hemihydrate was derived accordingly. The hydration process of the ß-hemihydrate was investigated applying an ultrasonic wave method and the influence of the water content on hydration was analyzed. The microstructure of the generated gypsum was studied by experiments and modeling. A model  was applied, which was successfully validated by the present experiments. Furthermore, the mechanical properties of the produced gypsum were investigated, and a numerical relation between water amount and strength was found.