Abstract: A test fixture for testing a flat sample of a material is disclosed. The test fixture having a test vessel for a fluid selected to test the desired properties of the material. The test fixture having a housing with a first end, a second end, and at least one wall extending from the first end to the second end. The housing may have a cylindrical configuration, a parallelpiped configuration, or other geometries. An opening in the housing is provided for receiving the flat test sample such that the assembled housing and the sample form a pressure vessel with an interior chamber.