Take a soft-bristled brush and use it to gently remove any surface debris from the hat. Use a gentle touch to avoid grinding dirt into the straw and staining. The bristles on the brush should be as soft as possible to avoid puckering the straw. Brush straw hats gently after each use to prevent dirt buildup.
Begin by selecting a mild dish detergent. Using chemical applications can cause damage to the hat. Drop a soft cotton cloth (light cloth for light straw and dark cloth for dark straw) into a bowl of warm water mixed with a few drops of the detergent.
Gently wipe the surface of the hat with the soapy cloth using small circular motions to remove surface dirt. Rinse the soap suds off the hat using a different cotton cloth dipped in plain water. Be sure not to soak the hat with water.
To clean surface sweat and grime from the interior of the hat, repeat the cleaning method above, but wait until the exterior of the hat is dry, to avoid moisture saturation.
For best results, allow the hat to dry on a form or shaped stand to maintain the look and line of the hat.
Brighten a dull straw hat by wiping over the entire surface with a damp cloth dipped in alcohol. The alcohol should be diluted with water to avoid strong odors and over-application. Use dark cloths for dark straw and light cloths for light straw to prevent unintended staining or stripping of the natural fibers.
If a straw hat is showing its age or got caught in the rain one too many times, there is a chance that the fibers will soften and the hat will begin to lose its shape. A light coat with shellac gum resin will give both luster and strength. Mix the shellac with equal parts clear alcohol (such as rubbing alcohol) to ensure the resin is not too thick when applied. Always follow the directions on the label.
Straw hats that receive excess moisture will shrink, so use care when cleaning and applying maintenance techniques. For a water laden hat, turn the sweat band to face out and let the interior air-dry.