Experiments to Try at Home from the Adhesives Topic Week

Some adhesives are made from ingredients that include starch. You may be familiar with starch from baking; it is a white powder that looks similar to flour. Starch is a natural raw material. But where does it come from? What contains starch? In the first step, you will discover a method for detecting starch.

Find Out Which Foods Contain Starch

For this experiment, you will need:

  • Various items of food for detecting starch, such as potatoes, semolina, corn kernels, grains of wheat, cucumber, nuts, sugar, salt
  • Small spoons
  • Saucers, small shallow glass dishes or similar receptacles
  • Plastic pipettes for dispensing drops of Lugol's solution
  • Iodine solution or, preferably, Lugol's solution (iodine/potassium iodide solution); available from pharmacies or online, for example

You can use a substance called Lugol’s solution to detect the presence of starch. Lugol’s solution is a pink to purple colored liquid that contains iodine. You may be familiar with iodine from its use in medicine. Iodine-containing medicine is used to disinfect a wound, for example. Iodine also has another property, however: It turns dark blue or black when starch is present.

Conduct a preliminary experiment:

  1. First use a small spatula to put a spatula tip's worth of cornstarch into a test tube.
  2. Add 2 ml (½ teaspoon) of water and carefully shake the test tube.
  3. Now add 2 drops of Lugol's solution to the test tube.

What can you see? Has the color changed?

You can now conduct the actual experiment:
Choose a few items of food that you would like to investigate. For example, you can test whether potatoes, cucumber, corn, rice, bananas, apples or things like baking powder, salt or sugar contain starch.

Cut a small slice from a potato and put two drops of Lugol's solution onto it. What happens? Does a potato contain starch?

Repeat the experiment with the other items of food. A small quantity is enough for you to detect the presence of starch.

Obtain Starch from Potatoes

For this experiment, you will need:

  • 4 medium-sized potatoes
  • 1 old dish towel
  • 2 medium plastic bowls
  • 1 kitchen grater
  • 1 small fireproof container that can be placed in an oven
  • 1 measuring jug
  • Water
  • Oven
  1. Grate the potatoes.
  2. Add 300 ml (10 fl. oz.) of water to the grated food in the plastic bowl and stir with a glass rod.
  3. Put a dish towel above a second plastic bowl, pour in the mixture and squeeze out the water (liquid). Collect this liquid in a bowl and wait until some sediment settles at the bottom.
  4. Put the remaining mixture back into the first bowl and repeat steps two and three, but using only 200 ml (7 fl. oz.) of water. Wait five minutes and then carefully strain off the liquid. Leave the white residue at the bottom in the bowl.
  5. Put the residue into a dish and place the dish in the oven at 180°C (350°F) for 20 minutes.

After 20 minutes, the water should have dried away leaving solid potato starch in the dish.

Make a Starch Paste

A starch powder by itself is not sticky. What do you need to do to make it sticky? It's quite simple: heat a small amount of starch with some water.

For this experiment, you will need:

  • Cornstarch
  • Kitchen scales
  • Measuring jug
  • A small saucepan
  • Water
  • Stove
  1. Use the kitchen scales to weigh out 10 g (½ oz.) of starch and put it in the saucepan.
  2. Add 50 ml (2 fl. oz.) of water and stir everything well.
  3. Heat the mixture on the stove at a low heat, stirring the whole time.
  4. When the mixture comes to the boil, you can remove the pan from the stove.

When the mixture is cold, you can use it to try to stick together two sheets of paper.