 Silly String is often used during weddings, birthday parties, carnivals and other festive occasions, but it has also proven useful militarily to detect tripwires.Silly String is made of a mixture of components dispersed throughout a liquid solvent in the product’s aerosol can.These substances include a polymer resin that provides the string’s structure, a plasticizer to tune the physical properties of the string, and a surfactant that promotes foaming of the product.