Natural indicators relate information by demonstrating shifts in color to inform observers of whether materials are acidic or basic. The indicators, which are plants containing useful chemicals relative to pH levels, do not provide a numeric value for acidity or baseness. Common natural indicators are litmus, red cabbage and Hydrangea.
Chemical indicators function similarly to natural indicators. They are available for use as test strips made of paper, liquid suspensions and crystals. Chemical indicators are synthetic, meaning they are man-made, and do not occur in nature. These indicators are also useful for studying acid-base titrations, which use chemical indicators to reflect ranges of pH levels.