Stay-at-home science project: Leave secret messages with invisible ink
Invisible messages only require a tiny bit of lemon juice. You can use the rest to make a nice dressing. You're welcome. (Sandra Gutierrez /)Welcome to PopSci’s at-home science projects series. On weekdays at noon, we’ll be posting new projects that use ingredients you can buy at the grocery store. Show us how it went by tagging your project on social media using #popsciprojects.Movie spies are super cool. They always seem to possess some amazing, technological gadget that ultimately helps them dismantle an atomic bomb, save the queen, or stop the assassination of the Malaysian prime minister.But espionage techniques don’t have to depend on such intricate devices. Real-life spies have employed more analog methods—writing invisible messages with acidic liquids such as lemon juice is one of them.Teach your kids this simple trick and you can even reclaim a little privacy around the house by leaving secret notes for each other.But...