An emulsion comprising: water; hydrophilic particles; and hydrophobic particles; wherein the hydrophilic and hydrophobic particles form shells encapsulating a gas that are suspended in the water, said shells comprising an external layer of hydrophilic particles and an internal layer of hydrophobic particles adjacent to the layer of hydrophilic particles.
A coating material comprising (A) at least one kind of hydrophobic nanoparticles based on silica and (B) at least one kind of hydrophilic nanoparticles based on silica having a BET internal surface area of >300 m.sup.2/g; process for preparing it, and its use.
