White fabric is most attractive when it has no visible stain, and that makes this color difficult to maintain. With white hats, you have the additional problem of sweat, hair products, color, even flying debris as potential hazardous matter that can damage and discolor your white hat forever. The trick with anything white is to clean any stain as soon as possible. Leaving a stain for a day or even a week may result in a permanent stain that is extremely difficult to remove.
Apply cold water to the stains. Place a few drops of a liquid dishwashing soap on the affected areas. Rub the stains with the moistened cloth and allow the soap to penetrate the stain for a half hour.
Rub the area with a moistened cloth and then rinse. Lay the hat under the sun or a light source until it dries.
Throw your hat into the washing machine. This only works for hats made of polyester or cotton. Hats made of other synthetic fibers are too delicate to go in the washing machine and should be dry-cleaned.
Wash using a laundry detergent containing bleach. Use a gentle, cold cycle. Do not use the spin dry function as this may damage the hat.
Spin dry will ruin your white hat and shrink it. It will also make it lose its form.
Never wash a white hat that has feathers or delicate lace. Have it dry cleaned instead.
Never place a white hat in the dryer. This will permanently ruin your hat and cause it to shrink.