The cell type of porous materials correlates with performance attributes such as strength, fluid exclusion (or acceptance) and insulating properties. Closed cells impart water resistance, thermal insulation, buoyancy and resilience. Open cells determine properties related to filtration, acoustics and wicking. The standard technique used by the Foam pycnometers is that of gas expansion from a calibrated sample chamber into a reference volume. The solid and closed cell volume of the sample is calculated from the relationship of the calibrated cell volumes and the pressures before and after expansion. The closed cell percentage is calculated from the solid volume and the measured geometric volume of a rectangular or cylindrical sample. Open cell % is calculated by difference (100%-open cell % = closed cell %). Density is calculated from mass (weight)/volume and is reported as grams/cc. The UltraFoam 1200e and PentaFoam 5200e pynometers conform to ASTM D6226 "Standard Test Method for Open Cell Content of Rigid Cellular Plastics."