Ink and secret messages


  • Glass jar with lid
  • Nails (alternate: steel wool)
  • Vinegar
  • Tea
  • White Glue or mucilage
  • Kerosene or safer cleaning solution for degreasing
Soak the nails (or steel wool) in the cleaning solution to degrease. Transfer to a non-metallic container and cover with white vinegar. Soak for 48 hours. Boil tea - 3 or 4 tablespoons per cup of water - several minutes. Add equal parts of the nail juice and tea. Mix in a little mucilage or glue until it is thick enough to write with. Once on paper, the ink will turn black with age. This is an old standard, and has appeared in many books of science.

You can also make ink from old pecan or walnut shells. Crush a dozen or so shells in a cloth. Boil in 1 cup (250 ml) of water for half an hour to 45 minutes, or until the water is dark brown. Allow to cool. Strain into a glass jar. Add 1/2 teaspoon (2.5 ml) of vinegar and 1/2 teaspoon of salt.

Invisible ink

Heat sensitive invisible inks are usually fairly simple organic liquids that will appear invisible once they have dried on a sheet of paper, but will darken when held over a heat source. Lemon juice or onion juice work best, with milk or vinegar lagging close behind. They can be applied with a pen or toothpick. Allow to air dry (don't use heat to dry it). The dried paper is held some distance over a candle, or pressed with a hot iron. There is, of course, the danger of the paper catching on fire with the candle, or scorching under the iron, so take the necessary precautions. It will be a little smoky, but the message should appear fairly quickly. Prisoners of war used this method to sneak out messages, using their own sweat and saliva as ink.

Another invisible ink

An alternative is to use a cornstarch and water mixture. Mix about 1 tsp (5 ml) cornstarch to 1/4 cup (60 ml) of water. Cook it a bit (you can nuke it in the microwave for a minute, stirring once). Let it cool, and write your message. Once dry, sponge it with a solution of iodine (toxic!) and water (10 or so drops in 1/4 cup (60 ml) of water). Your writing will appear in a dark blue, and the paper will be a lighter blue. If you substitute lemon juice for the cornstarch solution, you will end up with white text on a light blue background. If you are artistically minded, you should be able to get some interesting effects using this information.

Still more invisible ink

This one is a little tricky to do, and does not always turn out completely invisible. The reacting chemical in the ink is phenolphthalein, which is a component of some laxatives. Phenolphthalein alone makes an invisible ink, but often the other components of the laxative tablet will give the ink a color. It will still produce a nice reaction. You need:
  • Laxative pills. They must contain phenolphthalein.
  • Washing soda (or another safe alkali)
  • Paper
  • Water
  • Jar for mixing
  • Plate
If the tablets you are using have a colored coating, it will need to be scraped off. Use 5 or 6 tablets. Crush the tablets with a spoon in a jar. Add a couple of inches of water to the jar and mix. Use this "ink" to write your secret message. Allow to dry. To make it visible, mix four teaspoons of washing soda with four tablespoons of hot water. Lay the paper over a plate where a bit of water has been poured. You want the paper to soak up the water and saturate. Carefully dribble the washing soda solution onto the paper, allowing the drops to spread over the entire surface. Don't touch the paper where the message is while it is wet, as this will smear it. The writing should appear pink.

Secret message eggs

are on the egg page.
© 1997- Brian Carusella All rights reserved.
Quotes and images not my own remain in the
copyright of the originator or else in the public domain.