This is another favorite demo of mine. Throughout the years I had mixed results. I finally figured out that Gold Medal all purpose flour works the best with some preparation. I sift a small bag of flour to reduce clumping and ensure the separation of particles. When doing this demo be aware of what kind of fire alarms/detectors are used in the building. In my classroom there is no sensor that will go off. Where I recorded the video, our school's multipurpose room, it (it was about 30 feet above the demo area) could detect the heat/smoke that was released (the alarm sounded about 1 minute after the actual demo).