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Light Patterns

In this activity, students use various objects to make patterns on light-sensitive paper by exposing it to the sun's rays.

Perhaps you have noticed that curtains or furniture will fade if they are exposed to sunshine? The sun's rays can cause material to change.

Light sensitive paper is a type of paper which is one of those materials very sensitive to the sun's rays. When light hits it, a chemical named Berlin green in the paper reacts with the sunlight to produce a new chemical named Prussian blue. Putting objects on top of the paper prevents the light from reaching those areas, so no reaction takes place.

After sun exposure when the paper is placed in water, any remaining Berlin green is washed away. But the Prussian blue that was produced where sunlight hit is not water soluble so it stays in place on the paper, exposing the pattern of objects that blocked the sun's rays from reaching the light sensitive paper.. 

Objectives

  • Observe a light-sensitive reaction.

Materials

  • Per Demo or Student:
    many small objects (washers, leaves, coins, buttons, keys)
    trays filled with water
    bright sunny day
    light sensitive paper

    Teacher Tip: light-sensitive paper may be purchased from: Boreal as Sunprint paper or Teacher Source as Nature Print Paper

Key Questions

  • What is being blocked by the objects on the paper?

What To Do

  1. Arrange objects on a piece of light-sensitive paper.
  2. Allow the paper to stay in the sun until the paper turns light (according to manufacturer’s directions).
  3. Immerse the paper in water, wait a minute, rinse, and allow to dry.

Extensions

  • Put some coins or buttons on ordinary coloured paper or construction paper. Leave it on a sunny windowsill for a few days. How are the results similar to or different from your light-sensitive paper?
  • Use this paper to test how effect different types of sunscreen are, track the movement of the sun (through a hole), examine the differences between the leaves of different plants or the feathers of different birds.