Ghostly Flame Uses Safety Science “Magic” to Teach Fire Forensics

Understanding the fire triangle

Fire requires three essential components: heat, fuel, and oxygen. Together, these are known as the fire triangle. If one of these elements is missing, a fire cannot start or will quickly go out.

When we light a candle, the oxygen is provided by what’s in the room. The heat is from the burning wick. And the fuel is provided by the solid wax. But wait, solids don’t burn — only gases can ignite and burn.

The solid candle wax goes through a series of physical changes to transform solid wax into a gas that can burn. Heat from the wick melts the wax, which turns into a liquid. The liquid is drawn up the wick and is vaporized into a gas. It is the gas that ignites and burns. This is combustion — the chemical reaction that results when heat, fuel, and oxygen produce heat and light: a flame!

You can also see this reaction when you blow out a candle and treat the smoke as fuel. When we blow out a candle, the smoke that rises isn’t just soot, it contains tiny particles and gases that can ignite. This is where the Halloween magic, aka safety science phenomenon, comes in — if you bring a flame close to the smoke, it will ignite and travel back down to relight the wick. This demonstrates how gases are the fuel for the fire, rather than solids.

Explore the fire triangle with this spooky candle investigation

Try this investigation in your classroom and check out the video below to see how it demonstrates the fire triangle in action — isolating the fuel leg of the fire triangle.

Safety alert: When conducting this experiment, be sure you are using a flame-resistant surface. Loose clothing and long hair should be secured. Remove any flammable materials from the area. Protect your eyes by wearing splash goggles.

Observing smoke as fuel:

1. Light a candle, and allow it to burn for a moment.
2. Blow out the candle.
3. Bring an open flame (using a lit, long-reach lighter) close to the smoke as it rises out of the extinguished candle.
4. The flame will travel down the smoke to attach to the wick, relighting the candle.

This hands-on investigation is just one small part of our Xplorlabs Science of Fire Forensics pathway. Check out the full fire triangle investigation and other fire forensics resources.