Cleaning mold/mildew off your well-loved straw hat:
The best way to clean mold or mildew off a straw hat is to vacuum it off with a brush attachment.
If that does not remove the mold/mildew:
Caution: Excess solution applied to mold on a hat will discolor the straw.
Storage: Hats that come with a Peter Beaton signature hat box should be stored inside the box with the included cone in order to preserve the integrity of its shape.