WHAT'S INSIDE SILLY STRING: THE SECRET'S IN THE SOLVENT

In the patent application for Silly String (1972), the inventors characterized it as “a pressurized or ‘aerosol’ can containing a composition of matter for producing a string of plastic foam.” “Such a combination, they continued, “has substantial play and decorative utility.” Apparently you can’t say “ultimate spiderweb war weapon” in a patent.
  1. Surfactant
    The string’s secret is in its solvent and its surfactant, neither of which the company will name—along with other stuff it won’t confirm. Surfactant is just a fancy name for detergent, which is amphiphilic—both hydrophobic (water repelling) and hydrophilic (water attracting). That attraction-repulsion combination helps glue together molecules in the solution so the string comes out in one solid, silly stream. The stickiness also helps the stuff lightly cling to surfaces—and people—after launch.
  2. Deionized Water, Solvent
    Shaking the can mixes the solvent-that-shall-not-be-named with the rest of the ingredients, forming a temporary blend of plastics, minerals, and propellants. Both the water and the solvent quickly evaporate outside the can, leaving the foamy solids behind.
  3. 1,1,1,2-Tetrafluoroethane
    The aerosol powerhouse that sends the mixture flying is a relative of Freon-12, the ozone-depleting refrigerant that pressurized first-gen Silly String back in 1972. Inside the can, this propellant is in a compressed liquid form; when you hit the ­nozzle to rain silliness upon your enemies, the pressure drop causes the liquid to boil and vaporize, expanding and pushing the goo out of the can.
  4. Polyacrylic Resin
    The string gets its structure from this durable polymerized plastic. Mixed into the can as a powder, it creates a viscous solution. But once the plastic is propelled into the air, it forms a sturdy exoskeleton. The shell will stay in place for weeks if you never quite get around to tying up the loose ends of your Fright Night festivities.
  5. Talc
    Without talc, the string would be all plastic skin and no body, like a joke that falls flat. Made up of mostly magnesium, silicon, and oxygen, this absorbent mineral gives the resin substance, filling out the string as it expands to the size of the can’s nozzle.
  6. Isopropyl Alcohol, Ammonia
    These two ingredients help keep the solution stable so it can last between Halloweens. The alcohol prevents bugs from growing inside the can. The ammonia—or other basic compound—raises the pH enough so the can’s metal interior won’t corrode. After all, nothing is less silly than rusty Silly String. (📷 The Voorhes)