What material you use for making wicks for oil lamps?

Cotton wool is used for making wicks for oil lamps. Cotton wool comes from cotton bolls i.e. the fruits of cotton plants. 

[Recapitulation: Natural fibres are those fibres obtained from nature (plants and animals).

Plant fibres are obtained from plants.

Example:

Cotton fibre is obtained from the fruit of a cotton plant known as cotton bolls. Cotton plants are usually grown in places having a warm climate. Black soil is used to grow cotton because black soil is clayey in nature. Hence, they are also known as black cotton soil. They retain moisture in high content and are fine-grained dark colour soil. They contain high levels of Calcium, Magnesium, and Carbonate. All these are required by the cotton plant for its growth. 

After maturing, the bolls burst open and the seeds covered with cotton fibres can be seen. From these bolls, cotton is usually picked by hand. Fibres are then separated from the seeds by the process of ginning. This is known as cotton wool which is then used for making wicks for oil lamps.