Activity: The usefulness of wood ash
Aim
To understand that wood ash has chemical properties that make it useful.
Wood ash has properties that have made it useful in many cultures. It has been used to clean teeth and make soap.
Toothpaste
Besides using wood ash to produce dyes, some cultures including some iwi Māori have traditionally used a paste made from a fine powdery clay and wood ash to clean their teeth. The wood ash reacts with the acid made by the germs in your mouth and turns the acid into salt and water. This stops you getting tooth decay. This traditional toothpaste is not that different from the baking soda toothpaste sold in shops today.
Soap
The use of wood ash to make new substances has been a part of many cultures. Wood ash was mixed with vegetable oils by the Egyptians as long ago as 1550 BC to make soap. African people have been making soap for hundreds of years.
Soap can also be made from fat instead of oil. Fat comes from animals and is a solid at room temperature. Oil comes from plants and is a liquid at room temperature. The first soap was made by boiling wood ash in water and then boiling the liquid together with oil. This is difficult to carry out at school. The following activity is much easier.