Hydrophobic Coatings

This demonstration shows how hydrophobic coatings prevent water from soaking into a surface. By applying a water-repellent spray to sand or using wax crayons on paper, students can see how water beads up and rolls off instead of being absorbed.

DIY Sand Method:

1. Spread colored sand evenly in a plate or shallow container.
2. Spray the sand with a water-repellent fabric protector, coating it thoroughly.
3. Allow the sand to dry completely.
4. Place some of the coated sand in a clear plastic cup.
5. Add water slowly and observe how the sand clumps together instead of mixing with the water.

Wax-on-Paper Method:

1. Draw a thick patch with a wax crayon on a sheet of paper.
2. Drip water onto both the waxed area and the plain paper.
3. Observe how water beads up on the waxed surface but soaks into the plain paper.

The science of superhydrophobic surfaces - Imagination Station Toledo:

Science Max | Entire Outfit in HYDROPHOBIC Coating | SCIENCE - Science Max - 9 Story:

• Compare treated sand with untreated sand in water.
• Use different hydrophobic sprays on various fabrics or paper and test their effectiveness.
• Try dripping colored water to make the beading more visible.

• Perform spraying in a well-ventilated area or outdoors.
• Do not inhale spray mist.
• Wear safety goggles and gloves if handling sprays.
• Wash hands thoroughly after the activity.

• Why does water bead up on hydrophobic surfaces? (Because water molecules stick together more strongly than to the coated surface, due to surface tension.)
• How is wax similar to commercial hydrophobic sprays? (Both repel water because they are nonpolar and hydrophobic.)
• Where are hydrophobic coatings used in everyday life? (Rain jackets, tents, car windshields, stain-resistant fabrics.)
• How does surface tension contribute to this demonstration? (It helps water form droplets that roll off rather than spreading out.)