Geert-Jan Witkamp b, Jan Schippers a'c alnternational Institute for Infrastructural, Hydraulic and Environmental Engineering- IHE, P. (9. Box 3015,

• I n the supersaturated concentrates (2007 00 mg/1) depletion of silica monomers was c aused by the formation of polymers in s olution while the total silica concentration r emained constant. • T he silica gel seed deposition surface was n eeded to initiate the direct silica monomer d eposition. From supersaturated solutions, s ilica monomers deposited readily on silica g el seeds.