Colloidal silica is silica particles that are suspended in a liquid. The liquid is denser than water and has been stabilized electrostatically to allow the particles to stay suspended in the solution. The silica particles are also very small and do not have a large density. The range has to be approximately from thirty to a hundred nanometers. If the particles are too large, they will settle out of the solution. If the silica particles are too small, they are difficult to stabilize in a solution.