Silly String

Silly String is a child's toy, generically known as aerosol string: a flexible, brightly-colored plastic string, which is shot as a stream of liquid from an aerosol can. The string sets quickly in mid-air, allowing one to shoot a continuous strand of it. Silly String is popular for usage during weddings, birthday parties, school carnivals and other festive occasions. The material is a polymer-based resin which is propelled by the chlorofluorocarbon Freon-12, which is one of a group of compounds implicated in the depletion of the ozone layer. Within a year after Silly String was introduced, the US banned Freon 11 and 12 because they allegedly harmed the ozone layer. The formulation was immediately switched by Whamo and others to Freon formulations which were allowed. For this reason, the product has been banned in Canada.

History

Silly String was invented by Leonard A. Fish and Robert P. Cox who died in February, 2008. A patent was issued to them in 1972 as a United States Patent for a "foamable resinous composition". It is polymer-based, likely 11-16% polyisobutyl-methacrylate and 0.5 to 4% sorbitan trioleate dissolved in a CFC-based solvent (e.g. dichlorodifluoromethane aka Freon-12) that evaporates in the air and acts as a foaming agent. The pressure in the can propels the mixture a short distance of up to 20 feet. Some other alleged ingredients are a small amount of isopropyl alcohol, and plasticizers like dibutyl phthalate.

Silly String was licensed to and was produced by Wham-O, in a range of colors, until the rights were sold to Just for Kicks in 1997. The U.S. Patent #3705669 includes a clear description of preferred implementations.

The can is advertised to contain "over 400 feet of string". One measurement has shown over 1600 feet. For a 3.5 oz can, this equals 200 milligrams per meter.

Similar toys are Goofy String, Streamer String, Wacky String, and Nickelodeon Smatter. Silly String is also notorious for permanently damaging the vinyl surfaces of inflatable structures, upholstery, vinyl wallpaper, and automobile vinyl tops. It has been banned in the city of Marlborough, Massachusetts and a number of other places, and also at some public gatherings and events. The town board of Huntington in Long Island voted 4-1 to ban the sale of Silly String within 1,500 feet of the route of a parade.

Safety

The composition of Silly String is fairly safe, but the evaporating fluorocarbon can be quite cold, theoretically capable of causing frostbite. The mixture is a very weak skin irritant. The solvent is somewhat flammable, although the solidified string is said to be flame-resistant. The flammability of Silly String as it comes out of the can has been highlighted in several home videos of Silly String sprayed near birthday cakes with lit candles, causing small but frightening fires. Users of the product should take care not to spray it near an open flame.

Silly string is banned in Canada due to the use of CFC's as a propellant and in December 2006, Tween Brands, Inc., a retailer of girls' clothing and accessories in the U.S., was fined $109,800 by the United States Environmental Protection Agency for "allegedly distributing canned confetti string damaging to the ozone." EPA said the product marketed under various names by the retailer damages the stratospheric ozone layer. The production and use of chemicals harmful to that layer is controlled by U.S. federal law.

Military use

Silly String and similar products have long been used by American and British forces to detect tripwires for explosive booby traps. To use it in this manner, the soldier stands in the doorway and sprays the material over the suspect area. If the string falls to the ground there are no tripwires. However, if there is a tripwire, the string will be suspended in the air without pulling the wire

As of 2006 it is being used by U.S. troops in Iraq for this purpose. However, because the material is an aerosol, it cannot be shipped privately to Iraq and it is not provided by official channels. Thus, 80,000 cans unintentionally got stockpiled in New Jersey. In October 2007, a shipping company with the required credentials was finally found.

References

External links

• How Stuff Works - Silly String