The invention concerns an insulating material comprising 20-80 wt. % of a ceramic matrix, 5-40 wt. % insulating microspheres, 0.5-15 wt. % of one or more binders, and up to 5 wt. % water. The material may also contain 0.5-4 wt. % deflocculant and 0.5-4 wt. % colloidal silica. The ceramic matrix comprises vitreous grains, notably atomized silica. The insulating microspheres are hollow spheres comprising 55-65 wt. % silica and 27-33 wt. % alumina.