1352218 Mineral fibre boards KOMBINAT KALI VEB 29 July 1971 35713/71 Heading D2B Heat insulating, flame proof and water and weather-resistant fibre boards are produced by mixing inorganic fibres e.g. slag or mineral wool asbestos or expanded perlite, magnesium oxide and/or hydroxide and, in solid form a non fibrous silicate e.g. sodium silicate, with water to form a suspension, dewatering and curing at elevated temperature and pressure e.g. 120-350‹C and 5 atmos. pressure. Particularly resistant boards are obtained by a further heat treatment at up to 1000‹C.