If you wear a hat when it is hot outside, you know that the brim of the hat absorbs your sweat, often giving your hat a yellow stain. These stains are similar to those you may find in white shirts you wore while sweating. However, it is not as easy to throw your hat in a washing machine to get it clean. While you can put it in the washing machine on a gentle cycle -- and with a hat shaper -- you often must treat the stains individually first.
Drip a little bit of hydrogen peroxide onto the yellow stains in the brim of the hat. You do not need to soak the area. Distilled vinegar can be used in place of hydrogen peroxide.
Scrub the area with a clean toothbrush to allow the hydrogen peroxide to work into the fabric.
Allow the hydrogen peroxide to soak into the hat for about 10 minutes.
Rinse the hydrogen peroxide out of the hat with water and allow it to air dry. If possible, wash the hat in the washing machine on the gentle cycle with warm water and detergent.
Mix some enzyme-based cleaner into warm water. Use just enough to fully dissolve into the water.
Soak the hat in the enzyme-based cleaner and water for 20 minutes to allow the cleaner to do its work. If it is an older stain, soak it longer, up to a couple of hours if necessary.
Wash the hat in the washing machine on gentle cycle with mild detergent to further remove the stains.
Mix 1/4 cup of baking soda with water to make a thin paste.
Spread the baking soda paste onto the hat with a toothbrush and rub it into the fabric.
Leave the paste in place for 10 to 15 minutes.
Rinse the paste clean with water and wash it in the washing machine on a gentle cycle with mild detergent and warm water.