The writing for this invisible ink technique is done using corn starch. An iodine solution is used to reveal the writing.
Time Required: 15-30 minutes
- Essentially you want to make a thin corn starch gravy. You will write using the gravy, allow the writing to dry, then reveal the message using an iodine solution.
- If you don't have a pre-made iodine solution, you can make some by adding a teaspoon of iodine to about 10 teaspoons of water. Set the iodine aside for later.
- Mix about 2 T cornstarch with 4 tsp water in a pan. Heat, while stirring, until smooth. You can boil the mixture to make a gravy - just be careful not to burn it!
- Remove the cornstarch gravy from the heat. Dip a toothpick, small paintbrush, or cotton swab into it and use it to write your message on paper.
- Let the paper air-dry.
- Brush a small sponge, swab, or paintbrush dipped in the iodine solution over the paper to reveal the hidden message. The message should appear purple.
- You can use simple corn starch in water to write the message, but the writing won't be as invisible as it is using corn starch gravy.
- If the heat source is a problem, try using very hot tap water to hydrate the corn starch rather than using a stove or hot plate.
- Iodine binds to the starch molecules to reveal the message.
- Try using other starches instead of corn starch, such as diluted mashed potatoes or mashed cooked rice with water.
What You Need
- Corn Starch
- Toothpick or Cotton Swab
- Hot Plate or Stove