All fireworks are not the same. For example, a firecracker and a sparkler are very different. A firecracker creates a noisy controlled explosion. A sparkler, on the other hand, burns over a long period of time (up to a minute) and produces a brilliant shower of sparks. Sparklers are sometimes called ‘snowballs’ because they have a ball of sparks surrounding the burning part of the sparkler.
Several materials are required for a sparkler:
- an oxidizer
- a fuel
- iron, steel, aluminum, or other metal powder
- a combustible binder
In addition to these components, colorants and compounds may be added to moderate the chemical reaction.
The fuel may be charcoal and sulfur, or a sparkler may simply use its binder (material used to hold the metal onto the stick) as the fuel. The binder is usually sugar, starch, or shellac. Potassium nitrate or potassium chlorate may be used as oxidizers. The sparks are glowing bits of metal. A sparkler formula may be quite simple. For example, a sparkler may consist only of potassium perchlorate, titanium or aluminum, and dextrin.
How Sparklers Work
Now that you’ve seen the composition of a sparkler, let’s consider how these chemicals react with each other:
Oxidizers produce oxgen to burn the mixture. Oxidizers are usually nitrates, chlorates, or perchlorates. Nitrates are made up of a metal ion and a nitrate ion. Nitrates give up 1/3 of their oxygen to yield nitrites and oxygen. The resulting equation for potassium nitrate looks like this:
2 KNO3(solid) → 2 KNO2(solid) +O2(gas)
Chlorates are made up of a metal ion and the chlorate ion. Chlorates give up all of their oxygen, causing a more spectacular reaction. However, this also means they are explosive. An example of potassium chlorate yielding its oxygen would look like this:
2 KClO3(solid) → 2 KCl(solid) + 3 O2(gas)
Perchlorates have more oxygen in them, but are less likely to explode as a result of impact than are chlorates. Potassium perchlorate yields its oxygen in this reaction:
KClO4(solid) → KCl(solid) + 2 O2(gas)
The reducing agents is the fuel used to burn the oxygen produced by the oxidizers. This combustion produces hot gas. Examples of reducing agents are sulfur and charcoal, which react with the oxygen to form sulfur dioxide (SO2) and carbon dioxide (CO2), respectively.
Two reducing agents may be combined to accelerate or slow the reaction. Also, metals affect the speed of the reaction. Finer metal powders react more quickly than coarse powders or flakes. Other substances, such as cornmeal, also may be added to regulate the reaction.
Binders hold the mixture together. For a sparkler, common binders are dextrin (a sugar) dampened by water, or a shellac compound dampened by alcohol. The binder can serve as a reducing agent and as a reaction moderator.
Putting it All Together
To summarize, a sparkler consists of a chemical mixture that is molded onto a stick or wire. These chemicals may be mixed with water to form a slurry that can be coated on a wire (by dipping) or poured into a tube. Once the mixture dries, you have a sparkler. Aluminum, iron, steel, zinc or magnesium dust or flakes may be used to create the bright, shimmering sparks. The metal flakes heat up until they are incandescent and glow or, at a high enough temperature, actually burn. A variety of chemicals can be added to create colors. The fuel and oxidizer are proportioned so that the sparkler burns slowly rather than exploding like a firecracker. Once one end of the sparkler is ignited, it burns progressively to the other end.
Sparks cascading off of a burning stick present a burn hazard and potentially a fire hazard. The chemicals used in a sparkler tend not to be highly toxic, but they aren’t edible. Sparklers should not be burned on cakes as candles or otherwise used in a manner which could lead to consumption of the ash.