Chemistry Experiments You Can Do at Home


How can I make invisible ink?

  • Evaporation
  • Combustion reactions
  • Acid/base reactions
  • Cotton swab or paint brush
  • Heat source (can be a light bulb)
  • Measuring cup
  • Paper
  • Baking Soda
  • Water
  • Grape Juice (optional)
  1. To prepare the ink, just mix equal volumes of water and baking soda and stir well.
  2. Take a cotton swab, paint brush, toothpick (or something similar) and write a message on a piece of white paper using the water and baking soda mixture you have prepared.
  3. Allow the “ink” time to dry. The water will soak into the paper and eventually evaporate, but the baking soda will not evaporate and it will be left behind.
  4. To read your invisible message there are a couple of options. One is that you can hold the paper to a heat source, such as a light bulb or gentle flame (don’t burn the paper!) This should cause the baking soda on the paper to turn brown, revealing your message! The baking soda burns faster than the paper, which is why it turns brown before the paper does.
  5. Another option is to spread purple grape juice, over the paper (you can use a paint brush to do this). The message should appear in a different color/shade compared to the rest of the paper. This works because an acid in the grape juice reacts with the sodium bicarbonate that you used to write your message.

Make your message visible again by carefully heating the paper over a flame. The baking soda will brown before the paper does, making your message visible. You can achieve the same effect by brushing grape juice over the paper. (Photo by Jim Fordyce.)


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