Abstract: An improved sol-gel process is disclosed for fabricating large monoliths of silica or ceramic material, which are substantially free of cracks. Following formation of the gel, but before the gel is dried, the gel is subjected to a hydrothermal aging treatment, in which it is heated in an autoclave to a temperature of between 100.degree. and 300.degree. C., for a time duration of at least about one hour. This hydrothermal aging treatment causes silica (or ceramic) particles to migrate and fill small pores in the porous gel matrix, such that the average pore size increases and capillary forces encountered in the subsequent drying step are reduced to a point where cracking of the gel is substantially eliminated.