This glass disk with a smooth ground edge is used to show the great adhesive force of water (or other liquids).
The unit is suspended from a sensitive spring balance (not included) with the disk just resting flat on the surface of the water. When an attempt is made to lift the disk from the water surface, the force required will be seen to be much greater than just the weight of the apparatus.
The disk is suspended by a single thread that passes through three small eyes. These threads are deliberately twisted to provide enough friction so that the disc may be readily made to hang in a level position.
Diameter: 7.5 cm