Formation of porous bodies

A method of manufacturing a porous body including the stages of placing a quantity of particulate material in a container capable of being made gas-tight, evacuating said container, admitting to said container a gas, compacting said particulate material at a temperature above ambient temperature to form a compact within said container under a pressure which results in the particulate material being bonded together around discrete gas-containing pores and also reduces the volume of the initially formed pores within said compact so that the gas in said pores is at a higher pressure than that in the initially formed pores, permitting said compact to cool while maintaining said pressure until a temperature is reached below which the material will not yield, removing said pressure, and subsequently heat treating said compact at a temperature within a range which permits the pressure within said pores to exceed the material flow stress and thereby expand to provide a porous body.