A tear tester has a stationary clamp and a movable clamp on a pendulum, means for holding this pendulum in a raised position, then quickly releasing it, and a scale that registers the arc through which the released pendulum swings.
Samples of paper or fil are clamped into the tester and nicked to start the tear; then the pendulum clamp is released. This tears the sample and the scale registers the arc, As the arc i sproportional to the tear strength of sample, calibration of the arc gives the tear strength.