A balloon is a flexible bag that can be filled with air or another substance.
Party balloons are mostly made of rubber and can be filled with air, helium, water, or any other suitable liquid or gas. When rubber balloons are filled with air, their shapes can last for weeks. When rubber balloons are filled with helium, they seldom can hold their shape for more than a few hours. The helium gas molecules are too small to be contained by the stretched rubber membrane. The molecules slowly escape through the gaps among the polymer molecules.
Children sometimes fill small balloons with water and throw them at (or to) each other. A popular game with this idea is a water balloon toss, where two lines of people stand across from each other and throw balloons back and forth until each one bursts.
In the last decade, some more expensive (and longer-lasting) helium balloons are made of thin, unstretchable, impermeable mylar films. The mylar balloons have attractive shiny reflective surfaces and are printable with color pictures and patterns. The most important attributes to mylar ballons are its light weight and its ability to keep the helium gas from escaping for two to three weeks. It is generally the material of choice for helium balloons.
Large helium balloons are used as high flying vessels to carry scientific instruments (as in weather balloons), or even human passengers.
Balloon artists are entertainers who twist tubular balloons into sculptures.
External link: work of a typical balloon artist
See also: Hot air balloon