Silly String has long been a mainstay of children's birthday parties and celebrations. Silly String comes in a can that is filled with liquid plastic that is under pressure. When the button is engaged, the liquid comes out of the can in a small stream and hardens mid-air. This leaves long strings of colorful plastic everywhere which is loads of fun for children.
Leonard Fish and Robert Cox invented Silly String in 1972, when it began being produced by the company Wham-O. Since that time, many other companies have released similar products, but the original product (although the company that produces it is now called Just For Kicks) retains the name "Silly String."
Silly String is bright, colorful and festive. Spraying Silly String at celebrates has long been done as an alternative or in addition to confetti.
Silly String is considered by some to be an environmental menace. Because it is a plastic resin, it is not biodegradable. In fact, is has been known to clog up sewer systems and as a result has been banned by a number of cities.
Another issue is the propellants that are used to allow the Silly String to exit the can. In the past, these have been CFCs (chlorofluorocarbons), which have recently been banned once it was discovered that these compounds can damage the ozone layer. However, there are still cans containing CFC propellants being produced in foreign countries that do not have stringent environmental laws.
Recently Silly String has been used in the Iraqi war to indicate the presence of dangerous trip wires. When sprayed onto a surface, the Silly String will land gently on the trip wire and expose it without causing it to explode.
There are personal risks associated with using Silly String. The propellants used in Silly String can be very cold, and can actually freeze skin as it exits the can. Silly String cans are also under pressure, and the contents are flammable, which poses a fire risk particularly when sprayed near an open flame (like a candle on a birthday cake). The plastic that makes up Silly String can interact negatively with vinyl, and can permanently damage it.