of fine granular silica and 3 parts by weight of water are mixed then heated to 80 u00b0 to 100 u00b0 c while agitating at ambient pressure for 10 to 30 minutes thereby producing a mixture of monosodium silicate sodium silicate and silica about 1 part by weight of the alkali silicate mixture and 2 parts by weight of the isocyanate terminated polyurethane prepolymer as produced in example 8 are mixed then agitated while heating to 40 u00b0 c to 80 u00b0 c for 10 to 30 minutes thereby producing a poly urethane silicate prepolymer about 1 part by weight of water containing 10 methanol 3 by weight of detergent 5 by weight of sulphonated castor oil and 2 parts by weight of the poly urethane silicate prepolymer are mixed thoroughly the mixture begins to expand in 3 to 15 minutes and expands 3 to 12 times its original volume thereby producing a tan tough poly urethane silicate cellular solid about 4 parts by weight of the isocyanate terminated polyurethane prepolymer as produced in example 8 0 1 part by weight of sodium carbonate 1 part by weight of a mixture of fine granular hydrated silica and hydrated silica containing si h bonds silicoformic acid are mixed then heated to 40 u00b0 to 80 u00b0 c while agitating at ambient pressure for 10 to 30 minutes thereby producing a poly urethane silicate prepolymer about 1 part by weight of water containing 25 by weight of sodium silicate 2 by weight of soap 5 by weight of magnesium oxide and 4 by weight of sodium salt of.