Write a chemical message

What can we use if we don't have fresh lemon juice or cotton swabs?

Use bottled lemon juice or white vinegar poured into the small bowl and replace the cotton swab by dipping a clean paintbrush, toothpick, or cotton ball to write your secret message.

My writing either stays visible after drying or never appears when warmed — what should I try?

If the writing stays visible after drying, blot excess juice and write with lighter, quicker strokes, and if it doesn't brown when warmed, have an adult apply steady gentle heat (iron on the lowest setting or hold the paper a few inches from a warm lamp) until the juice darkens.

How can I adapt this activity for different ages?

For younger children, have an adult dip the swab, guide simple shapes, and do the heating step, while older kids can write full messages themselves and experiment with different acidic liquids like orange juice or vinegar and varied heating methods.

How can we extend or personalize the secret message craft?

Personalize it by decorating the dry paper before heating, folding it into a secret scroll or envelope to share on DIY.org, or write duplicates with lemon juice, vinegar, and orange juice to compare which turns the darkest brown when warmed.