Acids and bases/Litmus paper

Many vegetable inks contain compounds which can be used for indicator paper.

Simple recipe for litmus paper:
 * 1) Chop up some red cabbage
 * 2) Add water to cover
 * 3) Bring to a boil
 * 4) Soak some blotting paper in the colored solution
 * 5) Let the paper dry

Experiment with dipping the paper into a variety of common acids and bases. The paper will change color. Other intensely colored vegetables can also be used to make litmus paper.

See also:
 * Acids and bases