Abstract: A method of producing highly homogeneous material, for constructing bone density phantoms used in calibrating CT machines and the like, dehumidifies the x-ray absorbing constituents of the material and combines them under vacuum to reduce the effects of absorbed atmospheric moisture and of air entrained by the mixing process. The binding polymer into which the x-ray absorbing materials are added is predoped with hardener to increase its viscosity to a point that prevents the migration of the components during the hardening process but that does not prevent their adequate dispersion throughout the mixture. Molds are filled by transferring the unhardened material through a tube connected to the bottom of the mixing vessel and to the bottom of the mold to further prevent the entrainment of air.