Materials you'll need
- Water
- Shallow plate or tray
- Star-shaped confetti or glitter (red, white, and blue for 4th of July!)
- Dish soap
Step-by-step tutorial
Step 1: Pour enough water onto your plate to cover the whole surface in a thin layer.
Step 2: Sprinkle a handful of star confetti over the water so the stars are spread across the surface.
Step 3: Dip your finger in dish soap to pick up one small drop, then touch it to the center of the plate — and watch the stars shoot outward like fireworks.
Pro tip: The experiment works best with fresh water each time. Dump the plate, rinse it, and refill to reset.
Learn more
When you touch soap to the water, it breaks the surface tension — the invisible "skin" that holds water molecules together at the surface. Soap has much lower surface tension than plain water, so the moment it hits the center, there's a tension mismatch: the plain water around the edges is still pulling hard, and the soapy water in the middle is not. That difference creates a rush of water moving outward, away from the soap, and the stars get swept along with it. Scientists call this the Marangoni effect: fluid always flows from areas of lower surface tension toward areas of higher surface tension. That's why replacing the water resets the trick. Once soap covers the whole surface, there's no tension difference left to create the burst.
