Turmeric as an indicator

Activity 2.5 makes turmeric paper. Mix a spoonful of turmeric (haldi) with a little water to make a paste. Dip a piece of filter paper in it till it turns yellow, let it dry, and cut it into thin strips. Do this with an adult.

Now put a drop of each sample on a strip. Most do nothing. Only some turn the yellow strip red.

Turmeric stays yellow in acids, stays yellow in neutral substances, and turns red in bases. So turmeric paper can spot a base, but it cannot tell an acid from a neutral substance: both leave it yellow.

You may have seen this at home. A curry stain (curry has haldi) on a white shirt turns red when you rub soap on it, because soap is a base.

Ashwin used it for a Guru Purnima card. He spread turmeric paste on white paper, let it dry, and wrote his wishes in his teacher's mother tongue, Odia. For the writing to appear red, he had to write with a basic solution, such as soap or baking soda solution.

Turmeric, the 'golden spice', belongs to the ginger family. Ayurveda uses it in many home remedies.