Capillary Flow/Gas-liquid Porometry is the most common method for characterizing the pore size of fabric/textile media . 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 gas pressure to force a wetting liquid out of through pores in a fabric media. The pressure at which pores empty is inversely proportional to the pore size, larger pores require a lower pressure than do smaller pores. The resulting volumetric flow of gas through emptied pores is also measured. Pore size is then calculated using the “Young-Laplace equation.”