An investigation of the slip preparation and casting of two magnesium-alumino-silicate glass powders has demonstrated the particular importance of the control of particle size distribution and slip viscosity in fabricating uniform glass-ceramics by powder methods. Measurement of strength and fracture toughness of fired material, coupled with particle size analysis and scanning electron microscopy has allowed interpretation of the quality of the material produced in terms of strength limiting flaws. Suggestions for the improvement of this type of material are made.