Silica hydrogels show fractal properties corresponding with DLCAA or R
LCCA. During aging silica is redistributed, resulting in reinforcement
of the tenuous structure and only slightly disturbing fractal geometr
y. In zeolitic precursors no mass-fractals are present, but SAXS spect
ra show strong indications for the presence of surface-fractals. Compu
ter simulations do confirm the experimental results.