The mass of the material with air in the pores is 1.2 times the mass of the equivalent volume of air. Due to buoyancy, if you were to weigh the material in a se

The mass of the material with air in the pores is 1.2 times the mass of the equivalent volume of air. Due to buoyancy, if you were to weigh the material in a sea-level atmosphere, you would find that its weight was 0.2 times the mass of an equivalent volume of air (which is where the 5x comes from). The only way to make it float would be to evacuate the air from between the fibers, which would make the mass 0.2 times the air volume, and would allow it to float.