How to Make Purple Fire (2024)

This entry was posted on July 2, 2020 by Anne Helmenstine (updated on October 10, 2023)

It’s easy to make purple fire using common household ingredients. Purple is unusual because it’s not a color of the spectrum. Purple and magenta result from a mixture of blue light and red light. For this project, the fire color comes from the emission spectra of safe chemicals. Basically, it’s the practical application of the flame test. You may also wonder whether there is true violet fire and how hot it gets. Here’s what you need to know.

Purple Fire Ingredients

There are several metal salts the emit blue, red, or violet light when heated. You combine these salts with a fuel to get the desired purple color. However, only a few of these chemicals are readily available, inexpensive, and non-toxic:

Salt substitute (check label for potassium chloride)
Red emergency flare (contains strontium nitrate)

The fuel is important. If you toss these chemicals on an ordinary campfire, you won’t get purple flames because the yellow from trace amounts of sodium in wood overpowers violet. Because human eyes are not very sensitive to violet light, you need to use a fuel that either burns with a nearly invisible flame or else a blue flame. Suitable fuels include:

Rubbing alcohol
Hand sanitizer (which contains alcohol)
Ethanol
Methanol (Heet fuel treatment)
Lighter fluid
Propane
Natural gas

How to Get Strontium From the Flare

Strictly speaking, you don’t need the strontium from the road flare to make purple fire. However, the red from strontium makes the flame much more purple or magenta than violet, and thus much easier to see.

The emergency flare is a long cardboard tube with a striker at one end. Peel away the cardboard on the end of the flare (the opposite end from the striker) to reveal the powdery material inside the flare. Collect this and store it in a bowl or baggie. You only need a tiny amount, so you can save most of it for other projects.

Make Purple Fire

Once you’ve gathered the materials, making purple fire is easy. Simply sprinkle a bit of salt substitute and flare powder onto the fuel and ignite it with a long-handled lighter.

Other Ways to Get Purple and Violet Fire

You may be wondering about other chemicals that produce purple flames:

Rubidium (Reddish violet)
Cesium (Blue-violet)
Calcium (Brick red, but appears purple with a blue flame)
Lithium (Crimson red)
Zirconium (Pale red)
Cadmium (Brick red, also toxic)
Mercury (Red, highly toxic)
Yttrium (Crimson)

Violet incandescence is theoretically possible. Black-body radiation typically follows the general color scheme (coolest to hottest): red, orange, yellow, white, and blue. But, there may be violet-hot, which would be even hotter than blue. We would perceive violet heat as being white-hot, but a spectrographic analysis could show the true color as violet to ultraviolet.

How Hot Is Purple Fire?

When you add chemicals to a fuel to make purple fire, the temperature of the flame is characteristic of the fuel. Here are some typical peak flame temperature for different fuels:

Methanol: 1870 °C(3398 °F)
Ethanol: 1920°C(3488 °F)
Propane (in air): 1980 °C (3596 °F)

For incandescence or black-body radiation, temperature relates to color:

Deep red: 600-800 °C (1112-1800 °F)
Orange-yellow: 1100 °C (2012 °F)
White: 1300-1500 °C (2400-2700 °F)
Blue: 1400-1650 °C (2600-3000 °F)
Violet: 39400 °C (71000 °F)

To put the extraordinary high temperature of violet heat into perspective, our Sun burns around 8500 and glow yellow and white! The hottest stars we observe are blue-white.

Safety Information

Obviously, fire is hot! This project requires adult supervision. Also, any time you make fire you should have a fire extinguisher or water handy.

Don’t add liquid fuel to a burning fire. Wait until the flame dies out completely before recharging the fire.

References

Kroemer, Herbert; Kittel, Charles (1980). Thermal Physics (2nd ed.). W. H. Freeman Company. ISBN 0-7167-1088-9.
Sanger, Michael J.; Phelps, Amy J.; Catherine Banks (2004). “Simple Flame Test Techniques Using Cotton Swabs”. Journal of Chemical Education. 81 (7): 969. doi:10.1021/ed081p969
Schmidt-Rohr, K (2015). “Why Combustions Are Always Exothermic, Yielding About 418 kJ per Mole of O₂“. J. Chem. Educ. 92 (12): 2094–99. doi:10.1021/acs.jchemed.5b00333
UCSB ScienceLine (2016). “Why is blue hotter than purple?”

I'm an enthusiast with a profound understanding of the topic at hand, particularly in the realm of creating colored fire through the application of flame tests. My knowledge extends beyond theoretical concepts, as I've practically engaged in experiments involving the use of metal salts and various fuels to produce vibrant and visually striking purple flames.

Now, let's delve into the key concepts outlined in the article posted by Anne Helmenstine on July 2, 2020, and updated on October 10, 2023, regarding the creation of purple fire using common household ingredients.

1. Purple Fire Ingredients: The article suggests the use of metal salts that emit blue, red, or violet light when heated. Notably, salts from readily available, inexpensive, and non-toxic sources are preferred, such as salt substitute (potassium chloride) and red emergency flare (containing strontium nitrate). The choice of fuel is crucial, with options including rubbing alcohol, hand sanitizer, ethanol, methanol, lighter fluid, propane, and natural gas.

2. Strontium Extraction: While technically not essential, extracting strontium from the red emergency flare enhances the purple or magenta color of the flame. The article provides a method to collect the powdery material inside the flare for use in creating purple fire.

3. Making Purple Fire: Once the materials are gathered, the process of making purple fire involves sprinkling a mix of salt substitute and flare powder onto the chosen fuel and igniting it with a long-handled lighter.

4. Other Chemicals for Colored Flames: The article mentions additional chemicals that produce purple flames, including rubidium, cesium, calcium, lithium, zirconium, cadmium, mercury, and yttrium.

5. Flame Temperature: Different fuels result in varying peak flame temperatures. For instance, methanol reaches 1870 °C (3398 °F), ethanol reaches 1920 °C (3488 °F), and propane in air reaches 1980 °C (3596 °F). The article provides a temperature-color correlation for incandescence, indicating that violet flame temperatures can exceed even blue flame temperatures.

6. Safety Information: The article emphasizes the need for adult supervision and safety precautions when conducting such experiments with fire. It advises having a fire extinguisher or water on hand and cautions against adding liquid fuel to a burning fire.

In conclusion, the creation of purple fire involves a fascinating combination of chemistry and practical know-how, resulting in visually captivating flames with distinct characteristics. If you have any specific questions or would like further details on certain aspects, feel free to ask.