Ever wondered why candies are different colours? Many candies contain coloured dyes. To see the colours used in Smarties® or M&Ms® candies, you can dissolve the dyes out of the candies using a technique called chromatography.

Materials:

• M&M® or Smarties® candies (1 of each colour)
• coffee filter paper
• cotton swabs
• water

Procedure:

1. Place the coffee filter paper upside down on a table top.
2. Place a candy in the centre of the paper
3. Dip a cotton swab into the water and hold it above the candy allowing a little water to drip onto the candy.
4. Repeat this fairly slowly until the candy is quite wet and the circle of water on the blotting paper is about 5 cm across.
5. In a little while you should be able to see rings of different colours around the candy.

How does it work?

The colour in the sugar coating of the candy shell dissolves in the water. The water is drawn out through the paper by capillary action and moves in a growing circle. The different inks which make up the colour move at different speeds and so they are separated.  This process is called chromatography. (The word “chromatography” is derived from two Greek words: "chroma" meaning colour and "graphein" to write.)

Using this process you can see some candies have just one dye while others are made up of more than one dye. Note that once the colour and sugar has been removed from the shell all the candies are the same colour underneath.

Try the experiment again with a different type of candies, magic markers, or other coloured substances such as food colouring and Kool-Aid.

Note: Activity adapted from multiple sources by NRC scientist Dr. Mike Day.