 It is silica-based and can be derived from silica gel or by a modified Stober process.The lowest-density silica nanofoam weighs 1,000 g/m3, which is the evacuated version of the record-aerogel of 1,900 g/m3.The density of air is 1,200 g/m3 (at 20 °C and 1 atm).