The above photos were taken during the creation of the "Particles in the Mist: See Radioactive Particles Decay with Your Own Cloud Chamber!" physics Project Idea. Radioactive decay particles are too small to reflect light and too small to see, but with a cloud chamber, you can confirm their presence and observe their movements by viewing the trail of ions they leave as they move throughout the chamber.
This science project guides students in the construction of a DIY cloud chamber made from household materials. To observe the process of radioactive decay in this project, you will need a safe radioactive source. You can buy a 210Pb needle or you can dismantle an ionizing smoke detector to get at the radioactive source inside. If you like to take things apart, grab your tools! (Note: This one will not go back together in the end!)