Cavity test structures are useful for testing physical properties and painting/finishing techniques for various materials. Nine cavity structures are sprued together and may be separated with a small cutting or snipping tool. Cavity structures with 4 holes have 4 internal cavities and those with 2 holes have 2 internal cavities. The individual cavities are separated by internal walls. The cavities allows you to test materials for porosity with various paints or finishing solutions or to experiment with methods to fill the cavities with fillers such as colored epoxies or glues to provide contrasting colors.
The oval shaped geometry is included on the sprue section to identify that the test structure has minimum geometries of 40 mils. This helps to limit confusion between test structures which appear similar but have different minimum geometries.