042 | How It Works
Aerosol cans are highly pressurised cylinders that use a gaseous propellant to expel their contents. The more common system is the liquefied gas system. Liquid product gets poured into the can before the propellant is forced in through the nozzle at somewhere between two and eight times its normal atmospheric pressure. Aerosol propellant was originally made from chlorofluorocarbons (CFCs), but as they are hazardous to the ozone layer, liquefied propane and butane are generally used now. The propellant has a boiling point lower than room temperature, but the intense pressure it is under stops it from boiling. Depressing the nozzle opens up an airtight seal, releasing the pressure. As the pressure is reduced the propellant boils and breaks up the product, forming a gas mixture of propellant and product. This gets pushed out through the newly created gap and out of the nozzle in the form of a fine spray. The pressure is reduced as the volume of product and propellant decreases, which is why each spray is slightly less forceful than the previous one. Thicker substances like shaving cream work in the same way but when the propellant is forced out it forms bubbles inside the product instead of dissipating, creating a foamy result. The exception to this is aerosol cans in which food, such as whipped cream, is stored. Propane and butane are not safe to ingest, so liquefied nitrous oxide, otherwise known as laughing gas, is used instead. Aerosol cans are traditionally made from a thin sheet of steel or aluminium wrapped in rustresistant tin. The cylinder is wrapped around a curved steel base and welded shut at the end to ensure the high-pressure gas cannot escape. Depressing the nozzle on an aerosol can opens up a seal inside the can.
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The inner workings of an aerosol can
Inside an aerosol can
The science behind how aerosols spray everything from deodorant to whipped cream
How aerosols turn liquid into gas Aerosol sprays can be used for everything from spray painting to topping cakes
WorldMags.net
The propellant, most commonly butane or propane, is forced into the can under high pressure.
Propellant
The system is spring-loaded so when the pressure is removed from the nozzle, the spring pushes up, resealing the system.
Spring
The tight seal keeps the pressure inside the can high until it is released.
Seal
The propellant dissipates into the atmosphere, leaving just the desired product.
Spray
“As the pressure is released the propellant boils and WorldMags.net breaks up the product” SCIENCE
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