the sol-gel process is the name given to any one of a number of processes in which solution or sol undergoes a sol-gel transition. At this transition, the solution becomes a rigid non-fluid mass. A specific example of a sol-gel process is the polymerization of TEOS in ethanol and water. following addition of a catalyst this homogeneous solution undergoes a sol-gel transition to a rigid gel consisting of silica and solvent filled pores.