Colored flames

QUESTION:

Why do you get pink colors when you put a garden hose inside a copper pipe and put the pipe in a campfire?

ANSWER:

Yes, a campfire is magical and mesmerizing, with the coals glowing and flames flickering, and sparks popping and showering. There is something very primeval in that fire. Perhaps it goes back to our ancestors, where fire was their only source of warmth and cooking food.

Campfire lovers have been known to take a short length of copper pipe, perhaps 12 to 18 inches long, and drill several quarter-inch holes every 2 or 3 inches on all sides of the pipe. They then insert an old garden hose into the pipe. A hose should be just a little bit smaller in diameter than the pipe. The cheap vinyl hoses seem to work best, rather than the more expensive rubber kind. Toss the assembled copper pipe and inserted garden hose into the fire.

The vinyl hoses contain PVC (poly vinyl chloride), and chlorine reacts with the copper pipe to form copper chloride. You get some blues and green flames from the reaction. Lithium chloride will produce pink flames, and strontium chloride red flames.

To enhance the campfire experience, a real romantic might want to play “Waltz of the Flowers” from Tchaikovsky’s Nutcracker Suite.

Stay upwind of the campfire. Do not inhale the fire’s smoke. One never knows all the chemicals that are in that stuff.

Some campfire enthusiasts with make little wax patties with various embedded chemicals. Put a small amount of chemical (quarter inch) into a Dixie cup. Pour melted candle wax into the Dixie cup to just cover the chemical. Quickly stir to get the chemical mixed in with the wax. Let the stuff cool and harden, then peel off the sides of the paper cup. The wax patty is ready to toss into the campfire.
Copper sulfate can be found in swimming pool supplies. Borax, calcium chloride, and Epsom salts can be obtained in cleaning and laundry supplies.

Copper sulfate will yield a green color. Borax will supply a light green color. Calcium chloride delivers a blue hue, and Epson salts generate a white color. Sodium chloride is just regular table sale and will produce a gorgeous orange flame.

Where do the colors come from? There is some neat physics and chemistry here. Let’s take copper. When copper is heated, the atoms are excited. That means that the electrons go to orbits further away from the nucleus and to higher energy states. When the electron returns rapidly to its ground, home, or steady state, the orbit is was in before being “excited”, the atom emits a piece of energy in the form of a photon, a little particle of light. In the case of copper, the level of return corresponds to green light.

It is a beautiful world we live in, and a basic understanding of light, color, atoms, and energy makes it even more beauteous!

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