Abstract: A surface of a hydrophobic microporous thermal insulation material is coated by first heating the surface of the microporous thermal insulation material so as to provide a hydrophilic surface layer on the hydrophobic material. Subsequently, a water-based coating, such as a water-based silicate adhesive, is applied to the hydrophilic surface layer of the hydrophobic material. An abrasive-and/or impact-resistant cover, such as a glass fibre cloth, may be applied to the coating.

Abstract: A microporous thermal insulation material is formed from an intimate mixture of a dry particulate microporous material and reinforcing glass filaments. The glass constituting the glass filaments contains not more than 1 per cent by weight Na.sub.2 O and preferably has the following composition:______________________________________ SiO.sub.2 50-100 percent by weight Al.sub.2 O.sub.3 up to 25 percent by weight B.sub.2 O.sub.3 up to 8 percent by weight MgO up to 10 percent by weight CaO up to 21 percent by weight Na.sub.2 O up to 1 percent by weight K.sub.2 O up to 2 percent by weight Fe.sub.2 O.sub.3 up to 1 percent by weight F.sub.2 up to 1 percent by weight.