Invisible writing
We all know that too much sun can be dangerous for us because of the damage UV rays, invisible to our eyes, do to our skin. This is why it is very important to use UV protection when out in the sun. This experiment will show you just how effective UV protection can be in blocking UV rays.
You will need:
For the volcano shape:
- 1 dark thin piece of cloth
- 1 dark cloth soaked in laundry agent with optical brighteners (UV reflective) or paper covered with fluorescent marker
- A UV-protection spray or cream
- 2 pieces of cardboard
- A set of stencils
- A UV lamp
- A pair of scissors
And last but not least ... a helping hand from an adult.
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Method
Ask all the students in a class to line up next to each other, just in front of the white board with the tallest at one end of the line and the shortest at the other.
First use the stencil (or your own free style) to write a message (such as "Science is cool") or draw a pattern on the pieces of cardboard.
Cut this message out with the scissors
Drape the dark piece of cloth over an outer hard cardboard frame, stretch it and staple it to keep it stretched across the frame
Hold the framed cloth above the second soaked piece of cloth and put the UV-light above the framed cloth. The UV light should penetrate the thin dark cloth easily so that the soaked cloth shines brightly.
Put the stencil over this framed cloth and spray all over with UV-protection spray
Remove the stencil and once again put the UV lamp above the framed cloth
This time, your message or pattern should appear as a shadow on the cloth below since this pattern is protected and the UV light is not allowed to pass through.
Enjoy this secret message board.