Red cabbage ph indicator

by Mildred
(New York)

Some fruits and vegetables contain a chemical that will change colors if it is mixed with acids or bases. A common example is red cabbage. Red cabbage contains a pigment molecule called flavin. This pigment can be used to indicate pH.


How to make your own pH paper using juice from red cabbage

1. Chop the cabbage into small pieces until you have about 1 cup of chopped cabbage.

2. Put the cabbage into the blender with about 1½ cups of water. Blend the water and cabbage until finely chopped.

3. Decant the fluid into a glass bowl, pouring through a strainer to remove the cabbage.

4. Store your red cabbage juice in a sealed jar until you are ready to use it.


How to use your simple pH tester

You can use your homemade pH indicator on any other solutions of interest. However, to test your "pH tester" use some common household solutions. Here are some suggestions: washing detergent dissolved in water, tap water, vinegar, lemon juice or milk.

• Add a few drops of the cabbage juice to your solution of interest, and note any color changes.

Red (pH 2), Purple (pH 4), Violet (pH 6), Blue (pH 8, Blue-Green (pH 10), Greenish Yellow (pH 12)


Tip: You can make your own pH test strips.

Take a coffee filter and soak it in your red cabbage juice solution. Allow it to dry. Cut the coffee filter into strips and use them to test the pH of various solutions.