Helpful Hint: To Remove Stains on Straw Hats… Do you know what the stain is? If it is organic, try peroxide! Do not use bleach as bleach will probably yellow the straw. You always have the option of putting a trim over it if it doesn’t work. The trick is to apply the peroxide then blot it from both sides until it is almost dry. After it dries completely, if you still have a stain, repeat. Make sure that you let it dry completely, as it will appear darker when wet. If the stain is chemical, you would need to use dry cleaning solvent.