What is Bubble Point Testing and Micron Grade?
This test is a common industrial test for estimating the maximum pore size of a material. A test piece is submerged in a wetting fluid such as isopropyl alcohol and a gas pressure until a bubble forms and breaks away from the porous surface. ASTM E-128 and ISO 4003 detail the test method that use Darcy’s Law to correlate between bubble point pressure value measured and the calculated maximum pore size. This calculated maximum pore is then multiplied by a pore shape correction factor to estimate the filter rating, also known as the “Micron Grade” for rating our products. Each industry can use a different shape correction factor, so there are differences in each manufacturer’s specifications and bubble point ranges for assigning the “Micron Grade”. Several different shape correction factors have been developed for calculating the maximum pore size values, depending on the type of porous material being tested since the nature of the pore changes for different materials. For example, a por
