 Other ingredients include silicon fluid (to make the strands easier to clean up), flame retardant, and a pigment for color.A key component in Silly String is its aerosol spray can and the propellant that ejects the product mixture from the can.The product originally used chlorofluorocarbon propellant Freon 12 mixed with Freon 11, both part of a group of compounds that damage the ozone layer.