Science Projects And Inventions

YOU NEED:

• Two sheets of blank paper
• A ball point pen

Want to send a letter secretly with no one the wiser? There is a simple way to go about it. Take one sheet of paper and wet it. Spread the paper over a hard surface like a smooth desk top, a glass window pane or a mirror. Now take a dry sheet of paper and place it over the wet one and write what you want to on the dry one by pressing hard with a ballpoint pen. Now remove the papers from the surface they has been placed on. The message you wrote is clearly visible as a water mark on the wet sheet of paper- When the sheet of paper dries, the writing disappears. It is back again like magic it the sheet is wet.

HOW DOES IT WORK?

The pressure created by the ball point pen on the dry sheet of paper changes the fibres of the we sheet beneath. This change in the fibres is invisible to the eye when the sheet becomes dry- It becomes visible when the paper is wet again.