A method is disclosed for forming an accurate stone cast from an impression of a body region, used for the purpose of prosthetic fabrication, such as dental crowns and artificial eyes and hearing aids. The initial step with this unique method is to first acquire a suitable amount of dental stone catalyst. One type of a suitable stone catalyst is calcium sulfate dihydrate. The dental stone catalyst is engaged onto the internal surface of the impression. This catalyst, placed in the area between impression material and stone, will act to hasten the initial setting of wet, mixed dental stone that is in closest proximity to the impression. The result is a stratified set of the stone. Setting of the wet, mixed dental stone occurs first at the impression/stone interface. The mixed stone better resists distortion upon setting and the resultant set stone cast is more accurate.