Fireworks

Fireworks Colours

WARNING!

This experiment needs to be carried out under adult supervision as it involves fire and heating materials which can burn or explode.

Have you ever wondered how they get the different colours into the fireworks? If you want yellow fire, do you add yellow paint to the mixture? No, that would not work. To see how the colours get into fireworks, you will need:

Ingredients

metal paperclips
pliers
boric acid (from the pharmacy)
creme of tartar (from the grocery)
salt
water
a clear, blue flame. If you have a gas stove, the burner will work very well. If not, you can use a candle, but the colours will be more difficult to see.

Please read the safety warning before you start.
Straighten several of the paperclips into long, straight wires. Dip the end of one of the wires into the water and then into the salt. Some of the salt should stick to the wire. Hold the other end of the wire with the pliers, so you don’t burn your fingers and place the salted end of the wire into the flame. The flame should change to a bright yellow. Dip the hot wire into the water, so you don’t accidentally burn yourself. Select a new wire and repeat the experiment with the boric acid powder. The flame should turn green. Try the creme of tartar and the flame will be lavender.

What is happening? Most of the light that comes from a flame is caused by solid particles burning inside the flame. As we have seen in past experiments, the yellow colour of a candle flame is caused by the burning of tiny bits of the element carbon. The blue flame that we started with does not contain solid particles, so it gives off very little light. By adding chemicals to the flame, we can give it different colours. The yellow colour caused by the salt is due to a chemical called sodium.

The boric acid contains boron, which produces green and the creme of tartar contains potassium, which burns with a lavender light.

This idea also applies to fireworks. When you see yellow fireworks, they contain the element sodium. Calcium salts are added to produce orange. Salts of strontium or lithium are used for red, and you get green by adding barium, boron or copper. Bright whites are produced by burning aluminum or magnesium metal. The next time you are “ooohing” and “aaaaahhing” over a fireworks display, keep in the back of your mind that you are also seeing a marvellous chemistry show at the same time.