An upright column is packed with particles of a first material so the particles touch one another and a network of voids is defined between the particles. The network will be substantially continuous. A second material is then introduced into the column so the second material penetrates the network and fills the voids. The mixture of first and second materials is then consolidated using heat to melt the first or second material, while the other one of the first or second material remains in a solid state and acts as a space holder. Thereafter, the material which acts as the space holder may be removed thereby to leave a substantially continuous porous network defined by the material which was melted. It is found that, by use of the method, a substantially continuous network of the material which is melted can be formed and that the other material can readily be removed and/or is more easily removed compared to if a mixture of first and second materials was formed prior to packing in a column or mold.