Take a biscuit time. Make a hole in the side just big enough to run a (bunsen) tube through. Connect the tube to something in the tin that you can put flour in, and that will get blown out if you blow down the tube. An old tobacco pipe would probably work. Fill the pipe with flour, put a lit candle in the tin, and close the lid (not too tight). Wear safety glasses (just in case)
Blow down the tube... BANG!!