The invisible ink experiment uses the naturally acidic nature of lemon juice to write invisible messages. By using the lemon juice as ink, a written message disappears once the juice has been given chance to dry. Heating of the paper then reveals the hidden message!

Suggested teaching points

• Introduction to acids
• Introduce the idea that chemical reactions are temperature dependent
• There are a number of alternative inks that students can investigate (e.g. using cabbage indicator to visualise the text, tonic water)
• Investigative techniques

This file contains a set of detailed instructions, suggested questions, suggested improvements and disposal procedures for this experiment.

Invisible Ink Experiment Instructions

Before attempting this experiment, please ensure that you have read the safety section in the document above and performed a complete risk assessment. If you have any questions, comments or feedback, please use these forms.