How to Make Homemade Spy Gadgets

Use lemon juice to send secret messages. Remember that blank paper is suspicious, so write something innocuous in standard ink. Professional spies suggest a grocery list. A pointed makeup applicator can work well as a pen with lemon juice, but many household items will allow you to write legibly in invisible ink. This is one of the easiest homemade spy gadgets. Apply heat to read your message.

Make fingerprint powder for your spy kit. This homemade spy gadget will require adult assistance. Pour a small amount of cornstarch into a porcelain or stoneware saucer. Take a second saucer and apply a flame using a long-handled candle lighter or candle. Soot will quickly accumulate. Scrape the soot into the cornstarch and stir. Keep adding soot until you have a gray powder. Dust fingerprints with this powder and lift off with clear tape.

Make a periscope to see over fences and around corners. Cut a 2-inch square in one end of your cardboard mailing tube with a craft knife. Cut a 2-inch diagonal slit at each corner of the square. Repeat on the other end of the mailing tube, cutting into the opposite side of the tube. Mount mirrors onto 3-by-4-inch cardboard squares with glue and insert into the slits in your tube. The mirrors should face one another. Use duct tape to close up the ends of your tube.

Turn a pair of ordinary swim goggles into spy goggles. This homemade spy gadget is all about looks, but can be fun for children. Use a permanent marker to color in the lenses of your spy goggles. Avoid washable markers for this project.

Add to the fun of homemade spy gadgets with an inexpensive digital camera or webcam hidden in a stuffed toy or other item. You might also consider passing along old cellular phones or Bluetooth headsets to your little spies.