Polyester shrinks only when it is washed at a very high temperature. In a typical washing cycle, clothing made from polyester should be washed and dried at the hottest water and highest heat setting. To successfully shrink polyester, the cycle should be repeated multiple times.
To achieve maximum polyester shrinkage, the clothing should be ironed at a low-to-medium heat directly after it is washed in hot water. It is important to make sure the water used during the washing is not too hot, as it can cause the polyester to harden. Extended high-heat washing can also lead to color fading of polyester clothing.