Re: I made ph indicator strips out of cabbage. Why doesn't it work with bases?

Food pigments using have one color for acid and another (or colorless) for 
base.

You can usually only get one color change (either to acid or to base), 
depending on the initial pH of the indicator.

If you would like to make a food pigment indicator for base, you should 
use a food which is colored when acidic, and look for the color change. A 
variety of foods would suit the purpose, including strips of paper dipped 
in beet juice, blueberry juice, apple peel juice, etc.

The pigment involved is anthrocyanidin, which has different colors for 
acid and base pHs.