Pictured above are two of the hats we are using. Both have a spiral braid construction, meaning that a long narrow braid of straw has been stitched together in a spiral to form the shapes of the hats. (The hat on the right has sections of lace pieced into the brim.) The straw has grown extremely brittle and dry from age, and the hats are starting to break apart where the braid is seamed to itself.
One technique that can be used to rejuvenate dried-out old straw is a damp towel wrap. Put an old towel in the washer and run it through a rinse cycle. Let the washer spin out the water from the chamber, but stop the spin cycle as soon as the water's spun out so that the towel remains fairly wet.
Place the towel over a large bowl and make a depression for the hat crown.
Set the hat in the bowl.
Cover it gently with the towel.
Make sure it is completely enclosed, and let it sit overnight.
This will restore some pliability to the straw.
To repair a torn portion of a straw hat, make a patch from several layers of sturdy netting in a matching color, like so:
Then use a thin needle to patch it, taking care to slide it between the weave instead of stabbing it through the pieces of straw.