Filson waxed cotton rainwear should not be washed, as detergents will strip the wax from the fabric and reduce its water resistance. Simply brush or wipe off dirt, and let the waxed cotton develop its unique character and patina. Periodically rewaxing the cotton will renew its water-resistant properties. How often to rewax is dependent on its use. The more frequently waxed cotton gets soaked or muddy, the more frequently rewaxing is needed. For most users, every few years is a good guideline.
Filson technical rainwear can be machine-washed in cold water with no bleach. It should not be dry-cleaned.