WIRED Staff
Science

What's Inside: Silly String

The solid spray's secret sits in the solvent.
  • 01
    Find out how they make this molecular marvel.
  • 02

    Surfactant

    A hydrophobic (water-repelling) and hydrophilic (water-attracting) combo—aka detergent—that binds the molecules into a solid, silly stream.
  • 03

    Deionized Water, Solvent

    Shaking the can isn’t just fun -- it also mixes the solvent with the rest of the ingredients. Once the water and solvent evaporate outside the can, it leaves the foamy solids behind.
  • 04

    1,1,1,2,-Tetrafluoroethane

    Inside the can, this propellant is in a compressed liquid form. When you hit the nozzle to slime your enemies, the pressure drop causes the liquid to boil and vaporize, expanding and pushing the goo out.
  • 05

    Polyacrylic Resin

    This is what gives the string its structure. It forms the sturdy exoskeleton that keeps all that goo together. It’s got staying power, too: The shell will remain intact for weeks if you don’t clean it up.
  • 06

    Talc

    Without talc, the string would be all plastic skin and no body. Made up of mostly magnesium, silicon, and oxygen, this absorbent mineral provides the resin with some guts.
  • 07

    Isopropyl Alcohol, Ammonia

    If you find an old can of Silly String in the back of your closet and it still works, thank these ingredients. The alcohol prevents bugs from growing in the container, and the ammonia keeps the metal interior from corroding.
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