Proof Plane

Proof Plane Consisting of an acrylic rod with brass disc of 50 mm dia. The proof plane is 18 cm long with a sphere that is 3.5 cm in diameter. The proof plane is used to safely transfer electrostatic charge from one body to another. You will find this spherical proof plane to be of superior quality during your electrostatic demonstrations.   A high-quality proof plane uses a spherical shape because a sphere will hold the greatest charge and retain it for the longest time.