Tag Archives: colored fire

Rainbow Flames Halloween Jack o’ Lantern

Rainbow Fire Pumpkin

Rainbow Fire Pumpkin (Anne Helmenstine)

Looking for an over-the-top science-y Halloween jack o’ lantern? Here’s my favorite… a carved pumpkin that’s both covered in colored flames and shoots fire from every orifice. The colors work much like the analytical chemistry flame test in which heated ions release a characteristic spectrum of light.

Materials

  • Real Pumpkin (fake probably would melt, which might be something to try, I guess)
  • Colorant
  • Fuel

You have a few household chemical options for the colorant. My personal favorite is boric acid, which is sold as a roach killer powder or as a disinfectant powder. It emits a green light when heated. Borax, sold as a laundry booster, also burns green. Another choice is copper sulfate, which I have found in granular form as a root killer. Any or all of these work well.

The best fuel for the exterior of the pumpkin is hand sanitizer gel, which is 60-65% alcohol. You can use just hand sanitizer, but for big interior flames, it’s nice to have rubbing alcohol, kerosene, or methyl alcohol (Heet fuel treatment). My favorite combo is methanol (Heet) inside the pumpkin and hand sanitizer on the outside of the pumpkin.

Alcohol and hand sanitizer burn with a blue flame. Natural salts in the pumpkin produce yellow and orange, while incandescence covers the other colors of the spectrum.

This is a carved Halloween jack o' lantern sprinkled with copper sulfate and coated with hand sanitizer. (Anne Helmenstine)

This is a carved Halloween jack o’ lantern sprinkled with copper sulfate and coated with hand sanitizer. (Anne Helmenstine)

Make a Rainbow of Colored Fire

  1. Prepare your pumpkin. Carve it. Don’t carve it. Whatever floats your boat.
  2. Either go outdoors or else place your jack o’ lantern on a heat-safe surface, such as a cookie sheet on top of a potholder. Unless you get crazy, it should be easy to extinguish the flames by blowing them out, but it’s never a bad idea to have a source of water or a fire extinguisher at hand,
  3. Smear hand sanitizer all over the outside of the pumpkin. One nice feature of the product is that you’re left with water when the alcohol burns off, which puts out the fire.
  4. Sprinkle your colorant inside and outside the pumpkin.
  5. Pour a small amount (couple of ounces) of fuel into the jack o’ lantern.
  6. Use a long-handled lighter to ignite the fuel.
  7. You can re-charge the fire after the flames go out. Don’t add fuel to a burning pumpkin! There is no need to add more colorant chemical, as it is not consumed.

The carving is up to you. It’s not even critical to clean out the seeds and other pumpkin guts, since you don’t need to reach your hand inside the jack o’ lantern to place a candle. Anyway, the interior get immolated if you do it right, so it’s sort of a self-cleaning pumpkin.

Ready to see it in action? Here’s my video…

Safety Info

It’s a FIRE project. It makes an excellent Halloween chemistry demonstration or holiday display, but should only be under the control of a responsible adult. Have fun, but please be careful. Also, don’t use the pumpkin for pie or otherwise ingest it following this project. The colorant chemicals are more harmful to invertebrates (copper) and plants (too much boron) than to people, but they aren’t food. The fuels range from bad-tasting (ethanol) to downright toxic (methanol or kerosene). Read the warning labels on the products you use.

Burning Bouquet of Dandelions

Burning Dandelions

Burning Dandelions (Anne Helmenstine)

I continued my experimentation into the colors of flames produced by dandelions with a bouquet of ‘wishes’ or seed heads. In Nebraska, dandelions are used for dandelion wine, but mainly are a weed. No one objected to getting the flowers cleared out their yard. Actually, I suspect they were glad the seed heads were going to be burned. The bouquet is pretty, burns instantly, and leaves little residue.

Fire Projects | Make a Glowing Flower

Make a Tabletop Fire Tornado: Red and Blue Flames

Red & Blue Fire Vortex

Red & Blue Fire Vortex (Anne Helmenstine)

It’s fun and educational to make a tabletop fire tornado or fire vortex. Why not experiment with color, too? The easiest variation is the green fire tornado, but you can use other chemicals and a similar technique to get other colors or even multiple colors. This fire tornado showcases red and blue flames.

Materials

  • mesh waste basket
  • lazy susan or turntable
  • strontium nitrate (emergency flare)
  • methanol (Heet fuel treatment)
  • heat-safe plate (Pyrex or stoneware are good choices)

If you don’t have methanol, a different alcohol or lighter fluid will burn with a comparable blue flame. I used strontium nitrate for red, which I got by cutting open an emergency flare and collecting the powder. You could also order pure strontium nitrate online or use another metal salt that burns red, such as a lithium salt.

Red & Blue Fire Tornado

Red & Blue Fire Tornado (Anne Helmenstine)

Instructions

  1. Set the waste basket on the turntable.
  2. Sprinkle a small amount of strontium nitrate (flare powder) in the middle of your plate.
  3. Set the plate inside the waste basket.
  4. Place the waste basket on the turntable.
  5. Dampen the strontium nitrate with the methanol and pour a small amount around it. Don’t get crazy with the fuel, at least until you know what to expect.
  6. Light the fuel and spin the turntable.
  7. You can let it go out on its own, blow it out, cover it with a pan, or douse it with water. The methanol burns quickly, so putting it out is not generally an issue. However, for the pyros out there who will get carried away, it’s good to know all the various ways you can safely extinguish the flames.

I tried this project a few different ways. It’s possible to completely isolate the two colors from each other by placing the fuel (methanol) in two small metal cups and adding a pinch of strontium nitrate to one of them. You set the cups inside the waste basket, ignite the fuel, and slowly spin the turntable. It’s a spectacular effect, but it’s not the safest activity, since physics will pull the cups outward as you spin the basket. I think you’d get good results sticking the cups to a base using a hot glue gun, but I have not tried it yet.

Make It Red, White & Blue

You can add aluminum or titanium flakes to get white sparkles. Burning a separate pile of Epsom salts with methanol can give you white flames, though in my experience most products have enough sodium contamination to give you more yellow than white. There’s magnesium metal, which would certainly liven things up… not recommending, just saying.

So, of course I had to make a video of this project:

Two Ways To Make Green Fire

greenfireGreen fire is one of the most vibrant forms of colored flames. It’s also one of the easiest to produce with common materials!

Borax or Boric Acid Green Fire

Borax and boric acid are two boron salts. Borax is sold as a laundry detergent booster or household cleaner. Boric acid is sold as a roach killer or as a disinfectant. Adding either chemical to a fire yields a vivid green flame. For best results, mix borax or boric acid with methanol, a type of alcohol, and ignite the solution. The alcohol will burn off, leaving behind a white residue from the boron compound. You can add more alcohol to produce more colored fire. The boron compound is not consumed, so it can be re-used.

Copper Sulfate Green Fire

Copper sulfate is used as an algicide and root killing agent. You can sprinkle copper sulfate on a fire to impart a green flame. It mixes well with rubbing alcohol to produce pure green fire. The copper compound won’t be consumed by the fire, so simply add more fuel to maintain the color. This compound also works on a wood or charcoal fire, although you can expect a rainbow of colors from the interaction with other chemicals in the fuel.