Spray insulating coating for refractory articles

A process for preparing an insulating coating to be applied to a refractory article by spraying or gunning, said process comprising the steps of:

• mixing lightweight aggregate, a binder, organic fiber, an additive to improve green strength, and a foaming agent to form a slurry, wherein said lightweight aggregate is selected from the group consisting of hollow ceramic microspheres, phenolic microballoons, mullite holospheres, perlite, vermiculite, bubble alumina, and mixtures thereof, wherein said binder is selected from the group consisting of colloidal silica, calcium aluminate cement, sodium silicate, and mixtures thereof, wherein said additive is selected from the group consisting of ball clay, lignins, saccarides, aliphatics, and mixtures, thereof, and wherein said foaming agent is selected from the group consisting of ionic surfactants, anionic surfactants, and mixtures thereof;
• and
• foaming the slurry in order that the coating may be applied at low pressures and to lower the density of the coating to improve insulating properties of the coating.