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SCIENCE

SEPARATING COLOURED INKS

Objectives

  • To understand that coloured inks are mixed to produce particular colours.
  • To understand that these inks can be separated, using filter paper and water.

Curriculum links

English National Curriculum:
Science 3: 2a, 2d, 3

Gateway story

The gateway is intended to stimulate discussion about the range of coloured inks available, and how these might be achieved.

Gateway elements:

  • Bottles of coloured dyes
  • Ink jet printer.

Ink jet printer: Three primary printing colours, plus black, are used to create all colours from a colour printer. Children can find this information when interacting with the gateway.

 

 

Approximate time required: 30 minutes

Resources needed

Per group:

Bottles of food colouring in a range of colours (e.g. red, blue, yellow, green)
4 Pipettes or droppers
5-6 Filter papers or circles of blotting paper
5-6 Yogurt pots or similar containers
Felt-tipped pens and/or Smarties, and/or black writing inks

Suggested organisation

Children can try this activity as part of a circus of related activities where they move on, in groups, from one to the next in rotation.

Carrying out the activity

In groups, children begin by experimenting with mixing different food colourings together, perhaps using different ratios of the colours mixed. They do this by using a pipette to mix only a few drops of each colour together. A record can be kept of their 'colour recipes' and a drop of the resulting colour placed next to the recipe. Children should thus appreciate that new colours can be mixed in this way.

The class are then told that colours can also be 'unmixed' or separated, using very absorbent paper and water. They set up their equipment as shown in the following diagram, which also can be copied and enlarged for the children's use.

The children can either colour a large spot in the centre of the paper with a coloured felt pen or try a spot of writing ink or place a Smartie on the paper (when it's in position).

The paper 'tail' is dipped in the water, and the paper rests on top of the yogurt pot. Gradually, the water is absorbed into the paper, and travels up towards the ink spot or Smartie. As the water moves out onto the circle of paper, it carries with it the different colours of inks which are within the ink mixture. Results should start to appear in 5-10mins.

Black and brown felt-tipped pens, brown Smarties and black writing ink produce the widest range of colours.

Each colour stops moving with water at different times, hence a series of concentric colour circles appears on the paper.

Children can keep the papers as a permanent record of the colour separation, and these add an attractive element to a display on the activity. In addition, children can produce a table of results listing, for example, all the separated colours in colours of Smarties, felt-tipped pens or writing inks.

Extensions / links

Science
Trials can be made using different brands of felt-tipped pens but of similar colours, to separate the colours, compare results and draw conclusions about the possible recipes used to create them.

Science
Children can use their own mixed coloured 'inks' made with food colouring, to try and separate the colours again to see if there is any correlation between their recipe and the results.

Art
Children can experiment with the ideas of colours running and separating in their artwork, on a small or larger scale, using wet paper and ink colours. Brusho ink powders can be used, as they are very vibrant.