Fibonacci Art Project. Gravity Painting :: A STEAM Art Project for Kids. 25 STEAM Projects for Kids. Invisible Ink (Lemon Juice) Invisible Ink (Other Methods) A letter from the Revolutionary War with lines written in invisible ink. Credit: Wikimedia Commons Last year, the US Central Intelligence Agency released documents detailing recipes for invisible ink from 1917 and 1918. Among the recipes was a favorite ink recipe of German soliders during World War I — crushed aspirin mixed with water. Though the ink is easily available, uncovering it required a complicated chemical developer. Other recipes in the CIA documents used solutions of iron, silver or copper salts as ink and developed the writing by heating the paper. 1. This is how my experiment turned out. Using lemon juice as invisible ink, before and after developing with heat. 2. But if spies intercept a message written with one of these inks, it’s likely they could decode it.
To solve this problem, I borrowed a trick from George Washington: using two different chemicals to write and decode the message. Maintaining ink supplies was crucial during Washington's day. 3. Catapult - Planning-Sheet. Sinking & Floating (Book w/ Exercises, Activities) Full List PBS Science Projects. Sci . Thermometer (PBS) Sci . Parachute (PBS)