A large trash can fitted with a flexible plastic membrane can be used to create giant smoke rings. Striking the membrane sends a vortex of air through a hole, which can be made visible with smoke to demonstrate air movement and Bernoulli’s principle.

1. Turn a large trash can upside down and cut an 8-inch (20 cm) circular hole in the center of the bottom.
2. Cut a piece of plastic shower curtain large enough to extend about 10 inches (25 cm) over the can’s open edge.
3. Secure the plastic tightly over the open end with a bungee cord to act as a flexible membrane.
4. Strike the center of the membrane sharply with a hand or stick to send a blast of air through the hole, forming an invisible vortex ring.
5. To make the vortex visible, fill the can with smoke (using a smoke machine or safe smoke source) before striking the membrane.
6. Observe the large, rolling smoke rings as they move through the air.

Smoke ring demonstration | Giant vortex canon - Lab Luminaries:

Giant Smoke Rings - Cool Science Experiment - Sick Science!:

📄 How to Make Giant Smoke Rings - Steve Spangler: https://stevespangler.com/experiments/air-cannon-smoke-ring-vortex-launcher/
📄 Air Canon Smoke Ring - Rookie Parenting Science - a smaller scale, using incense as the smoke source: https://www.rookieparenting.com/air-canon-smoke-ring/

• Try making smaller versions using a 5-gallon bucket with a 2–3 inch hole.
• Experiment with hole shapes (oval, square) to see how it changes the vortex.
• Compare different strike strengths to see how far and fast the smoke rings travel.

• Adult supervision required when cutting plastic or using sharp tools.
• Never blow smoke directly into faces of people or animals.
• Perform the experiment outdoors or in a well-ventilated space to avoid triggering smoke alarms.
• Handle smoke sources with extreme care and follow all safety instructions.
• Keep water or a fire extinguisher nearby if using smoke sources that involve combustion.

• Why does a vortex ring hold its shape as it moves through the air?
• How does Bernoulli’s principle explain the stability of the smoke ring?
• Why does air leaving the center of the hole move faster than air at the edges?
• What eventually causes the smoke ring to slow down and disappear?
• How do vortex rings in air compare to those formed in water (e.g., dolphins or whales blowing rings)?