K-12 Outreach Page, NSF Center for Environmentally Responsible Solvents and Processes Cabbage Juice Indicator Chemists use indicators to test whether a substance is an acid or a base.
Indicators work by turning a distinctive color in the presence of an acid or a base.
You can make your own indicator from red cabbage. You can also make indicators from the juice of elderberries, blackberries, or cherries. Chop red cabbage up finely. Boil a pint of water in a saucepan. Add the red cabbage carefully to the boiling water and take the saucepan off the heat.