5. What's in an aerosol?
Letting product out P.11 of 13 
An aerosol contains some product (such as a body spray) and some propellant. The propellant has two main jobs:
  • to create a pressure to push the product out
  • to help break up the liquid droplets and make a fine spray.

The pressure inside the can is trying to push the product out. All that’s stopping it is the valve. Opening the valve lets the liquid through. The liquid flows up the dip tube, through the valve and out through the actuator. The actuator is the plastic parton the top of the can that you press.

Valve construction
Picture 5.0 The parts of a valve.
How does the valve work?
The valve has a number of components:

A plastic stem with a hole in it. The product passes out through this hole when the valve is opened. The valve is kept closed by ...

... a rubber ring that slips over the stem. When closed, this seals the hole in the stem. When the actuator is pushed down, the ring is bent upwards and uncovers the hole - letting the product through.

The housing which supports the rubber ring and forces it upwards when the actuator is pushed down.

A cup that holds together the valve components and the can.

A spring that pushes the stem back up when the actuator is released; the rubber ring then re-seals the hole in the stem.

When the valve is assembled, the rubber ring sits on the housing. If the stem is pushed down by the actuator, the rubber ring is bent upwards and reveals the hole. Product then passes up the inside of the stem, through the hole and into the cup. This directs it up through the actuator.

Aerosol cans are under pressure. Never take a real can apart or try to look inside
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Question 9
Look at the paragraphs below and fill in the gaps.
As well as pushing product out of the can, the propellant helps to . The stops the product leaving the can until someone presses on the . Then a hole in the is uncovered because the is bent upwards.

Summary                                           Close
  • the propellant pushes product out of the can
  • it also breaks up the product
  • the valve stops the product leaving the can until the actuator is pressed