There are two types of sparklers – metal sparklers and morning glory sparklers. The next post will be about morning glories!
Metal sparklers burn much slower than other types of fireworks and have incredibly bright light. Their ingredients include a fuel, oxidizer, iron or steel powder and a binder. The fuel is often charcoal or sulfur (hence the nasty smells sometimes), the oxidizer is often potassium nitrate and the binders are sugars or starch. For a sparkler, all those ingredients are mixed with water, coated on a wire and then dried before being ready to ignite.
Sparklers are quickly becoming popular at wedding reception send-offs instead of using rice. Colored sparklers are made using the same metals that create colors in aerial fireworks. The downside to colored sparklers is smoke that is produced from the added metals. Therefore, gold metal sparklers are typically used to create the spectacular pictures because they have minimal smoke!
Excerpt from sciencebuzz.org