Multilayers of colloidal particles

A new technique has been developed by which alternate layers of positively and negatively charged colloidal particles, such as silica and alumina, can be deposited from sols onto a smooth surface such as glass. By this means films of controlled, uniform thickness can be built up, showing interference colors. By using uniform colloidal particles such as silica or polystyrene latex about 100 mμ in diameter as a visible indicator film, the adsorption of invisibly small particles, polyvalent ions, surfactants, and water-soluble polymers can be simply observed and studied.