Red cabbage is a tried & true pH indicator for your science lab. While you may have played with liquid indicator, you can also make this into indicator paper to save money on expensive pH strips, or powder for long term storage and use. At ~$2 a head, you can easily make 2 gallons of liquid indicator, plenty of paper test strips, or concentrated powder. You can do a wide range of pH experiments with this food safe indicator. You can also use this to test the pH of food and eat it at the end