High Pressure Capillary Flow/Gas-liquid Porometry is the most common method for characterizing the Pore Size of coated/laminated . Bubble Point is based on the fact that liquid is held in the pores of the test media. Using Capillary Flow Porometry, the simple principle of high gas pressure to force a wetting liquid out through nanopores in a coated fabric media. The pressure at which pores empty is inversely proportional to the pore size, smaller pores require a higher pressure than larger pores. The resulting volumetric flow of gas through emptied pores is also measured. Pore size is then calculated using the Young-Laplace equation.