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..