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Making Silly String

In 2006, British and American troops discovered they could spray Silly String down the hall or under the door and see otherwise invisible tripwires connected to explosive devices. For the first time, Silly String was taken seriously. Prior to that, it was manufactured strictly as a toy or gag, made famous in the movie "Big." The interaction of chemicals causes them to change from liquid in an aerosol can to actual physical string.

Things You'll Need

Polyisobutyl methacrylate, an acrylic resin
Sorbitan trioleate, a surfactant
Dichlorodifluoromethane, a propellant

Instructions

- 1
  Find materials that chemically react to one another inside a small aerosol can so that the liquid, when extruded, will turn into hundreds of feet of solid string. Silly String uses polyisobutyl methacrylate, an acrylic resin also used in making Lucite and Plexiglas.
- 2
  Get the resin to foam by using a surfactant, or surface-active agent. Sorbitan trioleate, the surfactant used in detergent is also used in Silly String. The surfactant makes it possible to modify stickiness.
- 3
  Use a propellant to force the other ingredients out of the aerosol can as foam, and help form the skin of the string. The original propellant used was dichlorodifluoromethane, or Freon-12. Because it depletes ozone, Freon 12 is not manufactured today,
- 4
  Form the structure that coats the foam and makes it string by using a ratio of 15% resin. Too much resin creates a heavier substance like caulking material, too little resin and the result is too fragile.
- 5
  Measure the ratio of surfactant to make sure it is about 5%. Any less and the result will be the consistency of mousse, and any more will be too sticky, making Silly String adhere to surfaces.
- 6
  Note that about 70% of the formula is propellant. As the chemical reaction causes the substance to foam and be coated with resin the propellant is what forces it out of the aerosol can as string.
- 7
  Add a plasticizer to strengthen the strands, and further reduce stickiness, with silicone liquid helping to make the string removable from surfaces such as carpeting. Pigment is used to make the string multicolored, and flame retardant is added for safety.

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