How do pressurised containers (e.g., for bodyspray) work?

Question

And is it possible to buy empty ones that you can fill with whatever you want, or even make one yourself? Thanks!

Answer 1

The aerosol propellant in a spray can, used to be CFC's but, since the advent of 'Global Warming' CFC are now more or less banned, particularly in Refrigerations systems.
Other low boiling point liquids are now used into which the product has been dissolved or mixed. When the spray nozzle is depressed, the pressure in the can is decreased and the liquid mixture boils causing partial vaporisation of the propellant and thereby maintaining the spray pressure.
(This is why the can becomes quite cool. As the liquid boils, its temperature drops to near the boiling point of the propellant. e.g. if the propellant is Butane liquid, it will boil at 31°F (-0.5°C) and maintain the vapour pressure in the can.
The pressure at normal room temperature is about 15psi.
Some aerosols simply use compressed air or other suitable gas.

Any good perfume shop should stock empty perfume bottles that can be filled with Eau-de-Cologne or whatever and have a pump bulb or plunger type action to atomise the contents with air pressure.

Never try to refill a liquid propellant aerosol can or bottle.
It could be very dangerous.

Answer 2

It all has to do with the aerosals that are in them. These chemicals boil at low tempuratures, and as they boil into gasses, pressure in the can increases. When the pressure reaches a certain point, the aerosal can no longer boil and the pressure remains constant until more of the other liquid is released, at which point more of the aerosal boils and the pressure returns to what it was before being sprayed.

Note how after spraying such a can for a long period of time, the can itself becomes cold. This is because boiling is an endothermic reaction, and as the aerosal boils, it absorbs heat from the can, making the can cold.

I can't imagine how this kind of can could be made without the proper machinery, but if you can get your hands on the right chemicals and bottle, I suppose it might be possible. I've never heard of them being sold empty... that would be extremely difficult to market.

Answer 3

An aerosol can contains one fluid that boils well below room temperature (called the propellant) and one that boils at a much higher temperature (called the product). The product is the substance you actually use -- the hair spray or insect repellent, for example -- and the propellant is the means of getting the product out of the can. Both fluids are stored in a sealed metal can.
There are two ways to configure this aerosol system. In the simpler design, you pour in the liquid product, seal the can, and then pump a gaseous propellant through the valve system. The gas is pumped in at high-pressure, so it pushes down on the liquid product with a good amount of force.


There are some good diagrams on the link too.

Answer 4

You can buy empty manually pumped spray bottles, or use empty ones sold with window cleaner or such. For more powerful applications like spray paint, you want an airbrush and a small compressor to do this yourself.

The aerosol cans just contain a propellant like propane or something (it used to be freon) that's liquid under pressure, but has a high vapor pressure, so it propels paint or whatever dissolved in it through a nozzle that either makes a stream or mist. You can do this yourself with regular air, but you need to compress it and buy a a device such as an airbrush to spray it.

Answer 5

The container contains pressure.

Well, if you want to get detailed, the container contains a propellant that becomes a very high pressure. This usually stays at the bottom and does not come out unless you are an idiot and you hold the can upside-down. Anyways, the high pressure fluid pushes on the contents of the can, and when you press the top spray thing on the can you create a hole, and the contents, under duch high pressure, seek a place of lower pressure, ie, outside the can. It then sprays.