Rainbow is multicoloured arc made due to the striking of light on water droplets. It is actually an optical illusion which means that it doesn’t actually exist in a specific spot in the sky. It depends on where you are standing and the position of the sun or other sources of light. Here, in this project learn how to make a rainbow in a jar with help of the concept of density.


This experiment focuses on density. Here we are making a rainbow in a jar using this amazing concept of density.


  • One or Two Tablespoon
  • A container of water
  • Different types of food colouring of good quality
  • A cup of sugar
  • A set of Five Glasses
  • A lot of patience and reliable practice.


  • Place the five glasses. Add three teaspoon of sugar for the first four glasses.
  • Now add a teaspoon of sugar to glass one.
  • Continue the procedure but with a slight difference. That is add two teaspoons of sugar to glass two, three teaspoons of sugar to glass three and four teaspoons of sugar to glass four.
  • Stir until the sugar dissolves completely.
  • Add different types of food colouring to each glasses.
  • Now pour the one-fourth of contains in glass four to glass five.
  • Next procedure is quite a tricky one.
  • Now move on to the next layer. Gently pour the contains in the next layer that is present in the glass three.
  • Note that it should not mix with first layer present in glass five.
  • One can do this by placing a spoon on the first layer and gently pour the mixture on it, so that it can minimize the splash.
  • The slower you do the better will be the results.
  • Repeat the same procedure for glass two and glass three.
  • Ensure that you fill the layers as the same width as the first layer.


Different levels of density are created when different amount of sugars are added. As you can notice the layer at the bottom of the glass was the heaviest and rest of the layers were placed on the top of each layer. The layers may mix sooner or later and that may be referred to the concept of dynamics. The effect lasts for a long period of time only when a greater difference in density.

Practise This Question

Barring Helium, the melting and boiling points of every noble gas lie within a range of 10 degrees Celsius – True or false?