Secret Messages

How can acids and bases be used to write secret messages? The teacher writes a message, such a note, a word, or a homework assignment, in lemon juice. Then a student sprays cabbage water on the chart paper to reveal the message.


1 c water + vinegar OR

1 c water + ammonia

pitcher of cabbage water (the purple indicator)

chart paper

cotton swabs

What To Do

DIP the cotton swab into the ink and use it to WRITE your secret message on the soft porous paper. ALLOW the message to dry completely.




READ the "invisible ink" message by MISTING it lightly with the spray bottle filled with the red cabbage water solution.

Try making different messages with the different solutions. Do they all appear the same way? In what ways are they alike and different?


What's Happening? Find out more about invisible ink.

Challenge. What other solutions can work as invisible ink, or invisible ink revealers? Share your results in our pH Exchange.


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