With a black felt-tip pen, write a three-letter word in large letters on a white piece of paper. Place the paper in a brown envelope, and insert that envelope into a white envelope. The writing on the paper should now be impossible to read.
Get a piece of dark construction paper or tear out a page from a magazine that is printed on both sides. Roll up the paper into a four-inch-long tube. When you hold the tube against the envelope, you’ll be able to read the writing inside.
How Does It Work?
Usually you can’t read the writing inside an envelope because of the light reflected off the envelope’s white surface. But the tube blocks that reflected light, so you see only the light coming through the envelope. Kindly follow for more awesome tips and tricks. Thanks. 
