Horsehair brush. A horsehair brush will be your felt hat's best friend. There are brushes made specifically for hats or you can use a soft shoe shine brush, as long as the bristles are 100% horsehair. Use a brush with light colored bristles for a hat that is light in color and vice versa for dark colored hats. To clean the hat, gently brush the hat in short strokes with the nap. If the hat is in need of a more intense refresh, the brushing can be combined with some light steam from a clothing steamer, iron, or even a tea kettle. Be careful not to overdo it with the steam, you don't want to reshape the hat, just a light surface coating will suffice.
Horsehair brush. If your felt hat is looking tired and dirty, take a brush to it. Use a horsehair brush, as those made with nylon bristles can be too abrasive for felt. A soft shoeshine brush can do the trick or you can buy brushes especially made for hats. Get a brush with light-colored bristles for use on a light-colored hat and vice versa for dark hats, as the color of the bristles can sometimes transfer to the hat. Gently brush your hat with the nap in small, counter-clockwise motions.
Even when you can’t see the dirt, give your felt hat a regular brushing; it will prolong its life.
Dust. Wipe with a slightly damp cloth.
Hair and fuzz. If your hat is covered with pet hair or fuzz, wipe it gently with a piece of tape. Wrap it around your fingers, sticky side out, and sweep it gently across the hat.
Smudges and stains. For a stain on a felt hat, start off by taking a gum eraser or a rubber sponge (like a make-up sponge) to the mark or smudge. There are also sponges made especially for hats and dry cleaning sponges can do the trick as well.
If the stain or smudge persists, try a cleaner made for hats like Scout Hat Cleaner. You spray it on, wait for it to dry into a powder, and then brush it off. For a grease stain, you can also try rubbing some cornstarch into it and then brushing it off.
For a straw hat, use ivory soap and a wet cloth and gently rub the stain.
Prolonging the Life of Your Hat
Handle it by the brim, not the crown. I’ll admit that I like doffing my hat by grabbing it by the crown. It just looks cool. But unfortunately, while it may be suave, it’s no good for your hat. All that pinching will weaken the crown’s ability to holds its shape or create a crease that can’t be fixed. Oils and dirt from your hand will also soil the hat. Take off or pick up your hat by grasping it at the front and back of the brim. Always handle your hat with clean hands to avoid transferring grime to it.
Allow wet hats to dry naturally. If you get caught in a rainstorm and your hat becomes soaked, allow it to dry naturally; artificial heat from a hair dryer or heater can distort or shrink the hat. Turn the sweatband out and place the hat on its brim on a towel to avoid creating flat spots on the crown. Shape the hat to its proper form; a wet hat will dry in the shape you leave it in.
Try to avoid ever getting a straw hat wet, as the moisture will cause the straw to swell, distorting the hat’s shape.
Never leave your hat in your hot car. Heat and sunlight can dry out, fade and shrink your hat. So don’t leave it on your dashboard or in your trunk, or sitting in front of a window at home.
When your sweatband gets wet and oily, flip it down to let it dry out. This allows the perspiration to evaporate instead of soaking into your hat.