A process for making calcined gypsum in slurry or powder form. The process includes adding at least two types of crystal modifiers to the slurry. The first crystal modifier is to control crystal morphology of the calcined gypsum (such as succinic and/or malic acid). The second crystal modifier is to prevent or retard setting to control set time (such as tetrasodium pyrophosphate (TSPP)) to form a water stable product. An accelerator is typically added at the site of use for specific applications such as setting type joint compound, media casting, exterior/interior coating, and sprayable fireproofing. A composition made by the process and a kit for using the composition are also disclosed.