How to Make Invisible Ink with Baking Soda

Easy instructions for making non-toxic invisible ink using nothing more than water and baking soda.

1. Mix equal parts water and baking soda.
   
   
2. Dab a cotton swab, toothpick, or paintbrush into the mix.
   
   
3. Write a message onto white paper, using the baking soda solution as 'ink'.
   
   
4. Allow the ink to dry.
   
   
5. Read the message. There are two possible ways to read it:
   
   • 1. Hold the paper up to a heat source, such as a light bulb. The baking soda will cause the writing in the paper to turn brown.
     
     
   • 2. Paint over the paper with purple grape juice. The message will appear in a different color.
     
     

• Grape juice concentrate results in a more visible color change than regular grape juice.
• The baking soda mixture can also be used more diluted, with one part baking soda to two parts water.
• Baking soda and grape juice react with each other in an acid-based reaction, producing a color change in the paper.

• If you are using the heating method, avoid igniting the paper - don't use a halogen bulb.
• Be careful not to use too much water in your invisible ink. This may cause the paper to become soggy.

• Baking soda
• Paper
• Water
• Light bulb (heat source)
• Paintbrush or swab
• Measuring cup
• Purple grape juice (optional)