Science, Tech, Math › Science How to Make Invisible Ink Using Lemon Juice Share Flipboard Email Print Bettmann/Contributor/Getty Images Science Chemistry Projects & Experiments Basics Chemical Laws Molecules Periodic Table Scientific Method Biochemistry Physical Chemistry Medical Chemistry Chemistry In Everyday Life Famous Chemists Activities for Kids Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate By Anne Marie Helmenstine, Ph.D. Chemistry Expert Ph.D., Biomedical Sciences, University of Tennessee at Knoxville B.A., Physics and Mathematics, Hastings College Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels. our editorial process Facebook Facebook Twitter Twitter Anne Marie Helmenstine, Ph.D. Updated May 06, 2019 Use this easy recipe to make invisible ink. It only takes a few minutes to complete! Lemon juice is acidic and weakens paper. When paper is heated, the remaining acid turns the writing brown before discoloring the paper. Ingredients You only need a few simple materials to make invisible ink: Lemon or Lemon JuiceSunlight or Heat SourcePaperPaintbrush or Stick How to Make Invisible Ink Squeeze lemons to obtain their juice or obtain bottled lemon juice.Use the juice as ink by applying it to a stick or paintbrush and writing on paper.Allow the paper to dry.When you are ready to read your invisible message, hold the paper up to sunlight, a light bulb (recommended), or another heat source.The heat will cause the writing to darken to a pale brown, so your message can now be read.Another way to read the message is to put salt on the drying ink. After a minute, wipe the salt off and color over the paper with a wax crayon to reveal the message. Useful Tips Experiment with other juices. White wine, orange juice, vinegar, and apple juice all work well, too.A cotton swab makes an excellent disposable paintbrush.The writing turns brown because the weakened paper burns before the rest of the paper. Be careful not to overdo your heating and ignite the paper!