It's easy to make a rainbow of colored flames using common household chemicals. Basically, what you need are chemicals for each of the colors, plus a fuel. Use a fuel that burns with a clean blue flame. Good choices include rubbing alcohol, 151 rum, hand sanitizer made with alcohol, lighter fluid, or alcohol fuel treatment. You can get a rainbow effect by placing chemicals directly on burning wood or paper, but sodium in these fuels produces a strongly yellow flame, which tends to overpower the other colors.
Set Up the Rainbow
On a fire-proof surface, line up small piles of powder for each of the colorants. You only need a small pinch of each chemical (1/2 teaspoon or less). Usually, you'll run your rainbow red, orange, yellow, green, blue and violet (or the opposite direction). It works best if you try to keep the colorant chemicals separate. When the fuel is added, some of the colors naturally will run together.
Once the chemicals are set up, there's no hurry to light the fire. When you are ready, add fuel and then light it at one end. You'll get the most vivid coloring using methanol, but it burns hot. Hand sanitizer burns with the coolest temperature flame, but the high water content means the rainbow fire doesn't last long. Feel free to experiment. One compromise is to dampen the powders with methanol and follow up with a layer of hand sanitizer. As the fuel burns, the water will naturally extinguish the flames.
The colorant chemicals are not consumed by the flames, so you can add more fuel to renew the rainbow.
Table of Flame Colorants
Most of the chemicals used for the project can be obtained from a grocery store. All of them are available at a superstore, like a Walmart or Target Supercenter.
|Red||strontium nitrate or a lithium salt||contents of a red emergency flare or lithium from a lithium battery|
|Orange||calcium chloride or mix red/yellow chemicals||calcium chloride bleaching powder or mix salt with flare contents|
|Yellow||sodium chloride||table salt (sodium chloride)|
|Green||boric acid, borax, copper sulfate||borax laundry booster, boric acid disinfectant or insect killer, copper sulfate root killer|
|Blue||alcohol||rubbing alcohol, Heet methanol, 151 rum, or alcohol-based hand sanitizer, lighter fluid|
|Violet||potassium chloride||salt substitute|
Rainbow Fire Safety Information
- In addition to performing the project on a heat-safe surface, it's a good idea to do it in a well-ventilated area, under a fume hood, or outdoors. There may be a small amount of smoke.
- Do not add fuel to the fire while it is still burning. Wait until the flames are extinguished and then add more alcohol and re-light the fire.
- The flames are easily extinguished by blowing them out, suffocating them (as with the lid of a pan), or by adding water.
- It's a good idea to wear protective eyewear and clothing, as for any science demonstration. Avoid wearing synthetic fabrics, as they readily melt if exposed to flame. Cotton, silk, and wool are good choices, or you can wear a lab coat.