Liquefy six large red cabbage leaves in a blender half full of water. Strain the contents of the blender and keep the liquid. Fill three clear glasses half full of cabbage juice. Put a piece of white paper behind them. Add some vinegar to one glass and stir. The cabbage juice turns red indicating vinegar is an acid. Add some laundry detergent to a different glass and stir. The indicator turns green because the detergent is a base. Keep the three glasses to use for comparison. Use a small amount of cabbage juice indicator to test other substances, such as ammonia, milk, orange juice, cola, lemonade or soap.
Put cabbage juice indicator in a glass container. Put several pieces of filter paper in the cabbage juice to soak up the juice. Hang up the filter paper to dry. When the filter paper is dry, cut it into thin strips about 1/2-by-2 inches. When you want to find out if a liquid is an acid or a base, dip the homemade pH paper briefly in the liquid. The redder the color, the more acidic the liquid is. The greener the color, the more basic the liquid is.
Put the contents of a Pixy Stix in 1/2 cup of water and allow it to dissolve. Measure 1 tsp. of baking soda and spread it over the water. Bubbles will begin to form. When baking soda is combined with an acid, it produces carbon dioxide. You can test other sour candies by crushing them before adding them to water.
Fill one glass half full of vinegar, another glass half full of ammonia and a third glass half full of distilled water. Using commercial pH paper with a pH scale on the container, test the liquid in each glass and record the results. The vinegar, an acid, will have a pH of about 4 and the ammonia, a base, has a pH of about 12. The pH of pure distilled water is between 5.6 and 7. Most distilled water does not have a neutral pH of 7 because it turns acidic as it mixes with carbon dioxide from the air. Neutralize the distilled water by adding 1/8 tsp. of baking soda and retest the pH. Continue until it tests at 7. If add too much baking soda, add a drop of ammonia and retest.