From the California Car Duster website:
"Because of a special permanently baked in paraffin treatment, The Original California Dusters are made to provide years of effective service without the need for cleaning. Simply shake them out before and after each use. The "dirtier" they get the better they work.
If you find it necessary to clean your Duster because it is too dirty or if the Duster stops lifting dust, it can be washed. You may hand wash your Duster in cold water with a mild detergent such as Woolite, then air dry. Do not use hot water to wash or hot air to dry, as heat or harsh detergent may remove the special paraffin treatment."
Doesn't sound like you ruined it, unless you threw it in the dryer
