To prepare the indicator, shred some red cabbage leaves, place them in small volume of water (1/2 cup) in the pot, bring the pot to a boil on the stove, and boil for 5-10 minutes (Note - You should wear some form of eye protection and use pot holders when handling boiling solutions). Pour the water with the boiled leaves through the coffee filter to remove the pieces of cabbage, collect the filtered juice in a clean glass, and let it cool; it should appear purple. You can then pour the juice into the eyedropper bottles for use and storage. This filtered juice is your pH indicator. Note that the concentration of the indicator solution depends upon the amount of cabbage and the volume of water used; the more cabbage in the smallest possible volume of water will yield a high concentration of indicator molecules.
To use your pH indicator, pour about 2 teaspoons (10 ml) of each test substance into a separate Dixie cup. To each cup, add approximately 1/2 teaspoon (2 ml) of cabbage juice indicator. Now watch for the color changes! If the substance is an acid (i.e. lemon juice), the indicator should turn bright pink. If the substance is neutral (i.e. Gatorade), then the indicator should remain reddish-purple. Finally, if the substance is a base (i.e. window cleaner), then the indicator should turn green.