A knit hat can be stretched by soaking it in warm water and detergent, wringing it out and stretching it to the desired shape. To keep the hat stretched to the desired shape, put it over an object such as a jug or bowl.
When hats are stretched using the soaking method, mild detergent should be added to the water. Allow the hat to soak for 20 minutes. The hat should be damp before it's placed on the forming object. Tug the hat slightly in different directions so the hat stretches evenly. Allow the hat to dry completely before wearing it.