Vertical load testing, also known as head load, compression and axial-load testing, is carried out using a Hounsfield compression tester to determine a products resistance to vertical load forces.
This is commonly used to assess container glass packaging (e.g. bottles, jars, vials) which undergo palletisation, capping or stacking. However, the equipment is also used for assessment of flat glass strength using 3 or 4-point bend and ring-on-ring testing.
Vertical load strength of glass containers is determined for both pass/fail and progressive (to destruction) testing against the method in BS EN ISO 8113:2004, 'Glass containers. Resistance to vertical load. Test method'.
Below is an example of vertical load testing of a bottle to destruction. The stress within the glass, not usually visible, has been imaged using a polariscopic filter.