Botanical Anthocyanin Invisible Ink Acid-Base Reveal

30 mins Ages 10-14 Indoor

A challenging, hands-on discovery and STEM project designed for curious young minds aged 10 to 14.

Materials Needed

  • • Baking soda (Sodium bicarbonate) (1 tablespoon)
  • • 100% purple grape juice or boiled red cabbage broth (1/2 cup)
  • • White bond printer paper (2 sheets)
  • • Cotton swabs (Q-tips) (3 units)
  • • Fine-mist spray bottle (or soft foam brush) (1 unit)

Pro Tips

  • → Dissolve 1 tablespoon of baking soda in 2 tablespoons of water to create an invisible alkaline writing ink.
  • → Write a secret message on paper with a cotton swab and let it dry completely until invisible.
  • → Sponging or spraying purple grape juice or red cabbage juice over the paper turns the alkaline writing blue-green, revealing the hidden text.

Safety First

Non-toxic; protect work surfaces with newspaper from staining grape or cabbage juices.

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Step-by-Step Instructions

1

Step 1

Dissolve 1 tablespoon of baking soda into 2 tablespoons of warm water until clear.

2

Step 2

Dip a cotton swab into the clear liquid and write secret messages or maps onto white printer paper, letting it dry completely.

3

Step 3

Pour concentrated 100% purple grape juice or red cabbage indicator liquid into a clean fine-mist spray bottle.

4

Step 4

Lightly mist the dry paper to watch the alkaline baking soda letters react, turning teal-green against the purple page.

What they are learning

Invisible ink chemical developer reactions Acid-base anthocyanin indicators Historical espionage steganography