The aerosol was invented in 1941 by the American scientist Lyle David Goodhue. It first came onto the market in the early 1950's, since that time it has been utilised as a dispenser for a vast range of commercial commodities such as hair spray, insecticides, furniture polish and deodorants.
The spray is produced using a canister that contains a pressurized propellent such as butane (better known these days as a Chlorofluorocarbon or CFC). The propellant is a liquid that boils at everyday temperatures, it is partly liquefied due to the pressure within the can. Above the liquid is a layer of free gas, as the can is operated and the contents empty, the liquefied gas vaporizes and fills the space.
The aerosol functions when finger pressure is applied onto the nozzle which opens the valve and, due to the high internal pressure, causes the liquid to be forced up the plastic dip-tube and out of the nozzle as a fine spray. The propellant which emerges with the spray immediately evaporates into the air.
It has recently been discovered that CFC's have a detrimental effect on the earth's ozone layer. Many aerosols are now termed `Ozone friendly', using a less damaging propellant or a pump action on the nozzle to force out can contents under pressure.
