|1. The product. This is a solution or suspension of the substance that we want to spray. In this case, it is an aqueous solution of a water-soluble glue. |
2. The propellant. In this case, the propellant is a liquefied mixture of butane and propane (LPG). The gas has been put under pressure until it turns into a liquid (this happens at about 2.1 x 105 Pa). The space above the liquefied gas is taken up by butane or propane vapour. It is the pressure from this vapour that pushes the product out of the can. As the product gets used up, more of the LPG will turn into vapour, keeping the pressure constant.
3. The actuator. When you press down on the actuator, it opens ...
4. ... the valve and allows the product to be pushed out. The structure of the valve and the nozzle help determine the features of the spray.
5. The dip tube. The dip tube goes down to the bottom of the can to make sure it is always dipped in the product and that you always get all of the product out.