Once you've reached an age where sparklers are no longer fun, it's time to upgrade to science and steel wool. It may be basic chemistry, but as you'll see in the video, simplicity can amaze more than complexity, as well as create some really impressive fireworks that are perfect for the Fourth of July.
A fire wire makes use of the rapid oxidation of iron and carbon that is possible within the fine strands of steel wool. Because the strands are so thin, there is a massive surface area of exposed metal. When initiated with the energy of a lighter or 9-volt battery, the steel begins to react with the oxygen in the air to form Fe2O3 and Fe3O4, commonly known as rust. The reaction produces enough energy to heat neighboring strands of steel wool to the point where they also begin to react. The steel will then continue to oxidize until it has all been changed to rust, or has collapsed into a mass that no longer allows enough air in for a reaction.
This process is rapidly accelerated when the steel wool is spun by a wire because more oxygen is forced into the reaction. At the same time, pieces of burning steel break away as it burns, creating the effect seen in the video.
A fire wire throws off thousands of very hot sparks, so it should absolutely not be used in dry areas or where fires are likely. A wide brimmed hat or hood should also be worn to lessen the risk of burns, and safety glasses are necessary to protect the eyes. Only cotton or wool clothing should be worn when using a fire wire or any other fireworks, as synthetic fibers are flammable and can melt to the skin.