Photo by Jacob Kiesow on Unsplash

It’s getting hot in here with our Fire and Light show taking over our Science Theatre this half term, and our fiery show will see our science communicators set money on fire, play with the colour of flames, and even set light to a fire tornado. Don’t worry, the Health and Safety is all in place and no one’s leaving with singed eyebrows.

As we study the fire triangle and perform exhilarating experiments this half term, we’ve decided to dig into the science of fire. More specifically, we answer one burning question- what makes fire change colour?

The colours of flames come from two things…

While colour can depend on temperature, chemical reactions often take most of the credit. A fire itself is the result of a chemical reaction known as combustion, where fuel and oxygen react with one another and atoms rearrange themselves irreversibly.

For this to occur, fuel must reach its ignition temperature, and combustion will continue if there is enough fuel, heat and oxygen.

Once the temperature gets hot enough for the chemicals in the fuel to react with oxygen, it results in a colourful reaction. Red colours are the coolest flames, while lighter colours represent scorching temperatures.

In wood fires, the colours also come from the substances burning within the flames. The fierce orange flame is due to the presence of sodium, which emits once heated, copper compounds transform into green or blue, and lithium turns into red.

Why does fire burn blue sometimes?

The colour of flames is not limited to the glows of warm reds and oranges, and most of us have probably seen a blue flame.

The colour of a flame is influenced by oxygen supply, meaning that low-oxygen fires contain uncombusted fuel particles, leading to yellow glows. High-oxygen fires burn blue, and its flames are the hottest, defeated only by the heat of a white flame.

As with other colours, blue is a direct consequence of a chemical reaction, with carbon and hydrogen producing both blue and violet flames.

If you’re coming to visit us with the little ones over half term, don’t forget to pop in to the Science Theatre! For times and to book your tickets to Fire and Light, please see here.