An airtight chamber and piston system has been constructed that allows 3-gram samples of cotton to be compressed to selected porous or void fractions. Inlet and exit ports have been configured into the base and piston head, respectively, to allow the characterization of airflow through porous cotton plugs under controlled pressure. Instrumented components for monitoring air-flow rate and pressure conditions are added features, as is a controlled source of air and driving pressure. The sample chamber has been mounted on an Instron Universal Testing Instrument for providing control of compression rates and varying void fraction of the fiber samples. Preliminary results on a selected cotton and a round synthetic fiber demonstrate that fiber finenesses, as given by specific surface area, can be determined through air-flow measurements as expected. However, factors associated with compression needs to be taken into account. The computerized instrumentation and its operational parameters are outlined.