This may seem lengthy, just here me out.
We were in charge of making a science experiment for our finals. My group of friends decided to make smoke bombs. When our teacher found out she only had a half cup of potassium nitrate, we were disappointed. We needed three batches, and that meant there wasn't going to be much in each bomb. So we did it anyways. We mixed 99 grams of potassium nitrate and 67 grams of sugar-nearly perfect 3:2 ratio. I had made dispensers out of a cut up paper towel roll and some cardboard all covered in duct tape.We fried the mixture and poured in the holder.For the experiment, we put food color in one and clay in another. The fuse was a candle wick. The teacher had gotten in trouble letting kids outside. It was -20 degrees out. We had to light it inside. We were ready after all the groups had gone. We lined up all three against the back wall and I lit the first one. Several people were taping it. As the fire dipped below the card board, it smoked a little. Big deal. Then, FFFFFFWWWWWOOOOOMMMM!!! The thing was shooting flames four freaking feet up the wall! Our science teacher immediately threw the fire blanket on. While doing that, she tipped it over . When she took the blanket off, the one next to it started. More flames and screams. By that time the duct tape had started on fire and the things were belching black smoke. When the were put out, we had one remaining. There was black smoke all over the ceiling and the wall was charred black.We had to leave. I was running down the hall laughing my @$$ off. Our science teacher is the best. She was laughing so hard she was crying. Best school day ever.

We were expecting a bit of smoke, not flames! Potassium Nitrate is win!