The innocuous spray can has been the subject of some controversial press coverage over the years. Its use as a cheap means of getting "high," termed solvent abuse, involves inhaling the fumes of certain aerosols to achieve an effect a little like being drunk. The aerosol can is also popularly used to spray-paint graffiti and, during the 1970s, the increasing awareness that chlorofluorocarbons were causing damage to the ozone layer led to the use of CFCs being phased out in agreement with the Montreal Protocol. Despite the negative aspects of the product, the aerosol spray can is a ubiquitous invention that enjoys widespread use around the world today.
Aerosols date back to the late 1800s, with metal spray cans being tested as early as 1862. The real breakthrough in aerosol technology did not come until 1926 when Norwegian chemical engineer Erik Rotheim (1898-1938) discovered that a payload could be mixed with a propellant in a pressurized canister, allowing the product to be sprayed through a small directional nozzle.
The key to the aerosol is in the propellant. The gas used is stored in the can as a pressurized liquid vapor, at a temperature just below its natural boiling point (usually slightly below normal room temperature). When the liquid is released through the nozzle, it evaporates and turns into a gas, thus propelling the product in the form of a spray.
Despite its detractors, Rotheim's invention has brought improvements and greater convenience in many areas of activity, from spray paints that produce a satisfyingly even coat on refurbished cars to the improbable but appetizing arabesques of spray- administered whipped cream topping.
