3. Grains and water – Capillary bridges

The capillary bridge between two beads (1’04)

Water, in the presence of air, forms capillary bridges between solid surfaces. A capillary bridge is a drop of water that sticks to two solid surfaces. This drop takes on a very special shape and exerts a force that attracts the two solid surfaces towards each other.

Beads and water (1’24)

In the case of glass beads, the capillary bridges exert sufficient force to prevent them from moving apart under the action of vibrations.

In the case of sand grains, which are smaller and therefore less heavy, the force of the capillary bridges becomes preponderant. The wet sand grains stick together and allow sand castles to be made.

The glass slides (1’42)

By changing the shape of solid surfaces, capillary bridges can exert an even greater force compared to the forces of gravity.

Mini Exercise

The next quiz is an exercise. It does not count for any learning assessment.

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