Insert the glass tensile specimen into the universal tensile testing machine such that both of its shoulders are gripped at the two crossheads of the machine. Make sure the machine is well calibrated and recommended for testing brittle materials and it has the speed, precision and force capacity for testing glass. For example, a machine that is suitable for measuring long elongations may fail to work with glass which experiences vary short elongations.
Align the test specimen in the axis of tension by the testing machine. This is very important to prevent the machine from exerting bending forces on the specimen instead of tension forces. Use a U joint or spherical seat to minimize misalignment in the machine.
Assess your setup once more to make sure you have done it right and that the specimen is firmly gripped. Check if the output of the machine is working properly. Some machines draw a graph on a piece of paper during the test for the stress strain properties; therefore, make sure you place a suitable piece of paper in the plotter of the machine. On the other hand, some machines display the measurements on a computer screen which is easier to analyze than the former.
Start the machine. Follow a user manual for the machine to aid you on how to operate it or employ the aid of a technician knowledgeable in this field. The machine will now pull the glass specimen along its length, causing it to elastically stretch for a short period of loading before it finally breaks.
Observe the output from the machine and note values such as; the elastic limit which is the point which if exceeded, the material undergoes plastic deformation or rapture, the rapture strength which is the force at which the material breaks and ultimate tensile strength which is depicted by the maximum coordinate on the graph.