![]() ![]() Some shells contain explosives designed to crackle in the sky, or whistles that explode outward with the stars. They may contain stars of different colors and compositions to create softer or brighter light, more or less sparks, etc. Shells like this are called multibreak shells. More complicated shells burst in two or three phases. Since the explosion throws the stars in all directions, you get the huge sphere of sparkling light that is so familiar at fireworks displays. The explosion ignites the outside of the stars, which begin to burn with bright showers of sparks. When the fuse burns into the shell, it ignites the bursting charge, causing the shell to explode. The stars are poured into the tube and then surrounded by black powder. Stars come in all shapes and sizes, but you can imagine a simple star as something like sparkler compound formed into a ball the size of a pea or a dime. Simple shells consist of a paper tube filled with stars and black powder. It is also sprinkled between the stars to help ignite them. The powder is packed into the center tube, which is the bursting charge. The blue balls are the stars, and the gray is black powder. The shell's fuse burns while the shell rises to its correct altitude, and then ignites the bursting charge so it explodes.Ī simple shell used in an aerial fireworks display. When the lifting charge fires to launch the shell, it lights the shell's fuse. The mortar might be a short, steel pipe with a lifting charge of black powder that explodes in the pipe to launch the shell. In the next section, we'll look at aerial fireworks, such as those you might see in a fireworks display. A variety of chemicals can be added to create colors. The metal flakes heat up until they are incandescent and shine brightly or, at a high enough temperature, actually burn. It is very common for fireworks to contain aluminum, iron, steel, zinc or magnesium dust in order to create bright, shimmering sparks. The fuel and oxidizer are proportioned, along with the other chemicals, so that the sparkler burns slowly rather than exploding like a firecracker. When you light it, the sparkler burns from one end to the other (like a cigarette). Mixed with water, these chemicals form a slurry that can be coated on a wire (by dipping) or poured into a tube. The fuel is charcoal and sulfur, as in black powder. See this Question of the Day for a discussion of oxidizers - potassium nitrate is a very common one. If you look at Patent #3,862,865: Sparkler composition, you can see that a sparkler consists of several different compounds: Sparklers are often referred to as "snowball sparklers" because of the ball of sparks that surrounds the burning portion of the sparkler. A sparkler burns over a long period of time (up to a minute) and produces extremely bright and showery light. Sparklers are very different from firecrackers. A composition used in a firecracker might have aluminum instead of or in addition to charcoal in order to brighten the explosion. Black powder, discussed briefly in How Rocket Engines Work, contains charcoal, sulfur and potassium nitrate. They consist of either black powder (also known as gunpowder) or flash powder in a tight paper tube with a fuse to light the powder. The sparkler demonstrates how to get bright, sparkling light from a firework, and the firecracker shows how to create an explosion.įirecrackers have been around for hundreds of years. It turns out that if you understand these two pyrotechnic devices, then you are well on your way to understanding aerial fireworks. ![]() For example, you have probably seen both sparklers and firecrackers. Just about everyone in the United States has some personal experience with fireworks, either from Fourth of July or New Years Eve celebrations. ![]()
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