Ironing or smoothing is the work of using a heated tool to remove wrinkles from washed clothes. The common tools for this purpose are called "irons", though modern designs are no longer made of iron.
Ironing works by loosening the bonds between the long-chain polymer molecules in the fibres of the material. While the molecules are hot, the fibres are straightened by the weight of the iron, and they hold their new shape as they cool. Some fabrics, such as cotton, require the addition of water to loosen the intermolecular bonds.