Carbonated beverages like soda are more acidic with a pH of 3 while detergents are more basic with a pH around 10 and 11. Pure water is a neutral solution-it has a pH of 7. The paper is made with litmus, an organic dye that turns different colors. A very acidic solution is red, a very basic solution is blue, and a neutral solution is green. But it's pretty easy to make your own color pH indicator.
Indicators are organic dyes that change color when an acid or base is added.
Add enough water to cover the cabbage and boil it for 20 minutes. After cooling the boiled mixture for about 30 minutes, remove the cabbage and keep the dark liquid. The dark liquid will be your indicator. After eating a big dinner, you might take an antacid tablet with sodium bicarbonate in it to settle your upset stomach. The base in the antacid tablet neutralizes some of the acid in your stomach and should make you feel better.