It’s easy to make pink flames or pink fire if you apply a bit of chemistry. Here is a look at how pink flame work and suggested colorants that are readily available and non-toxic. That being said, it’s never a good idea to roast your marshmallows or cook burgers over colored fire. Simply sit back and enjoy it.
How Pink Flames Work
Flame colors come from the emission spectra of elements. The color you see is the combination of all the different wavelengths of light released when heat gives energy to electrons and the excited electrons release photons (light) when they return to a lower energy state.
But, heating a colorant does not necessarily produce a flame in that color. This is because burning a fuel also releases light. Other chemicals in a mixture also impact the final result.
Pink is not a color you see on the spectrum of visible light. It’s a designer color in fireworks because you combine colors from various reactions to get it. For example, red plus white gives pink. So, adding a white magnesium flame to a red flame (like from strontium or rubidium) yields pink. Toning down red also helps produce pink. Nitrates in a chemical formula help do this.
Start With the Fuel
For the best results, start with a colorless or blue flame. It is possible you can get pink flames in a wood-burning fire, but usually wood contains enough sodium that the yellow emission overwhelms other colors. Propane and natural gas work better. Get the best results using alcohol as a fuel because it burns with a colorless or blue flame.
Consider the solubility of the colorants in the fuel. For example, lithium chloride burns pink. But, it is more soluble in water or methanol than it is in ethanol. So, you can dissolve it into its ions in methanol and burn it for pink flames. Or, dissolve it in a small amount of water or 50% alcohol and mix this solution with 95-99% alcohol for pink fire.
Applying the solubility rules, most nitrates and many chlorides are soluble in water and at least somewhat soluble in alcohol.
Pink Flame Colorants
The basis for the colorants is the flame test in chemistry. Which colorants you choose depend on availability, toxicity, cost, and other factors. Most of these chemicals are available online. Some you can buy in stores. For example, strontium nitrate occurs in emergency flares. Potassium chloride is a salt substitute. Potassium nitrate or saltpeter is a stump removal chemical.
- Lithium chloride
- Lithium chloride + potassium nitrate
- Strontium nitrate + potassium chloride
- Strontium nitrate + potassium nitrate
- Rubidium nitrate
- Rubidium (nitrate or chloride) + magnesium
- Strontium nitrate + magnesium
- Strontium (nitrate or chloride) + copper(I) chloride
Of these chemicals, lithium chloride makes the easiest pink flames. But, unless you order it online or know how to collect it from lithium ion batteries, it’s not a practical choice. I typically mix strontium nitrate with either potassium nitrate or potassium chloride together in methanol (Heet fuel treatment) and ignite the mixture.
What You Do
Once you have a fuel and some colorant chemicals, making pink flames is simple.
- Start with a heat-safe container, like a small metal bowl.
- Pour a bit of the chemical (usually a powder) into the container.
- Moisten the colorants with the fuel.
- Using a long-handled lighter, ignite the fuel.
The chemicals don’t get used up, so you don’t need to add more to keep up the effect. What you do is wait until the flame is completely extinguished, add more fuel, and light it again. Never add fuel to a burning flame.
References
- Koch, E.-C. (2002). “Special Materials in Pyrotechnics, Part II: Application of Caesium and Rubidium Compounds in Pyrotechnics“. Journal Pyrotechnics. 15: 9–24.
- Wietelmann, Ulrich; Bauer, Richard J. (2005). “Lithium and Lithium Compounds”. Ullmann’s Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a15_393