Calibrate a pH Indicator Scale

How to Calibrate a pH Scale for Red Cabbage Juice

The scale shown was calibrated by KBolden. It gives you an idea of what a completed scale might look like. Notice that at the top and bottom of the scales, the color appear to be too make a distinction. If you get a color scale with more distinct colors, please share it with me.

The juice from red cabbage can be used as an acid/base indicator. For instructions to extract red cabbage juice, see


Prepare pH Indicator Scale

Find the pH of each of the different materials you plan to test. You can use the materials shown as well as other materials you wish to test.

Prepare a chart with the materials tested, their pH, and the color they are when added to the red cabbage juice.

Prepare Testing Materials

Prepare a clear, transparent, plastic cup for each material you wish to test. Label each of the cups with the name of the material.

* Solid Materials—Crush each solid. In its labeled cup, mix the crushed material with ¼ cup of distilled water.

* Liquid Materials—Pour ¼ cup of each liquid material into its own labeled cup.

Testing with Red Cabbage Juice

Add drops of concentrated red cabbage juice to each of the testing cups. Stir so that the juice and material are thoroughly mixed.

Record the color of the mixture in your pH Scale Chart.

33101X: Sticky, Gloppy, Wacky, and Wonderful Experiments Sticky, Gloppy, Wacky, and Wonderful Experiments