When dealing with vintage hats, purists never wear them, less strict collectors wear them when their hair is very clean, and nobody takes the aging hat out in a downpour. Stiff hats will collapse.
Keep a close eye on the weather when wearing vintage hats.
If you are caught in the rain with your felt hat, turn out the sweatband to dry it and to provide a platform for the hat to slowly dry on.
Gently push out the creases and dents to make the crown as rounded as possible.
Never use a hair dryer as this will wrinkle and damage the hat.
Once the hat is dry, gently reform the crease.
Dusting with Brushes
Whether vintage or modern, dust your hat daily with a soft-bristled brush.
Stiff bristled brushes will tear the felt.
Western stores frequently sell hatter's brushes for this dusting job.
Use a dark-colored brush for dark hats and a light colored brush for light hats.
Dusting with a Damp Towel
A damp towel with a slight nap can also be used to remove dust.
Gently rub the dampened towel in a circular counterclockwise motion over the surface to quickly remove dust.
A soft towel used to dry off with after a shower will work.
Remember, do not try this with a stiff hat, moist shellac is a terrible thing.
For stubborn stains the brush will not reach, try using a soft, small-pored sponge such as a makeup sponge or a bit of foam rubber.
Rubber sponges are slightly sticky and will coax surface soiling away from the felt.
An art-gum eraser will work as well, as long as your remember to rub with a counterclockwise motion to the grain.
For deeper stains, sanding is required.
Using the finest sandpaper on the market, move the sandpaper counterclockwise very gently and gently touch the dirty spot.
Be careful not to dig in or use your finger to push up against the spot from underneath as either of these will cause the sandpaper to dig in and create a weak spot.
When sanding is required, make sure to remove only the tiniest layer of felt.
Oily stains are a different matter.
For these you need to head to the paint or drug store and fine Fuller's Earth. It has the consistency of baking powder, will not stain hats, and will draw the oily residue out of the hat fibers.
Brush the stained spot off first. Apply roughly one-eight inch worth of Fuller's Earth, and let it sit for two or three hours.
Brush the powder off afterwards with a soft brush or towel. Repeat this process if necessary.
When finished, use a plastic or rubber sponge to clean away powder that has penetrated into the felt.
If stains remain after all of this, find a professional renovator for your hat. Heavy sweat stains, for example, need professional attention as they penetrate deep into the body of the felt.