Remember when Rhett Butler comments on Mammy’s new red taffeta petticoat when he hears it rustling? That sound is called ‘Scroop’ and is the distinct crisp, scraping sound made by silk taffeta. The sound is achieved by the silk being treated with a dilute acid that hardens the protein filaments. The sound is also achieved in rayon taffeta by using a similar treatment that hardens cellulose filaments.