[header] How to make homemade ph paper test strips [title] Chop up some red cabbage. [step] You'll need to chop about ¼ of a head of red cabbage and put it in a blender. You will extract chemicals from the cabbage to coat your ph paper. 
These chemicals are known as anthocyanins and are found in plants such as cabbage, roses, and berries. Anthocyanins are purple under neutral conditions (ph 7.0) but they change color when exposed to an acid (ph [7.0) or a base (ph]7.0).