How does spray paint work?

Have you ever wondered how spray paint works? The reason it comes out of the can like it does is down to the combination of a gas propellant and the paint.

When the cans are manufactured, they are initially filled with paint before being injected with gas propellant. The valve is crimped, which traps the compressed compound inside the can. This is the method behind why it releases from the can the way it does.

Before 1978, the propellant of choice were chlorofluorocarbons but once it was discovered they depleted the ozone, they were banned. Manufacturers turned to hydrocarbons until the 1980s when it was discovered they caused smog. So, today manufacturers use hydrofluorocarbons, containing carbon, fluorine and hydrogen which don’t present so much of a risk to the environment.

Why is there a ball bearing inside? The pea-sized metal ball bearing ensures that when the can is shaken, the components are mixed well. If the two components were allowed to settle, they would come out unevenly and the paint would form clumps.

Thanks to the clever combination of chemistry, physics and mechanics, spray paint has become an incredibly useful tool in home improvement. However, the science behind spray paint is not limited to home DIY, and there are heavy-duty industrial applications that use spray paint.

The benefits that home improvers enjoy – such as no wastage, even coats and quick application are all benefits enjoyed in large-scale industrial settings as well.

When it comes to industrial spray painting, the most common methods are vacuum coating, flatline spraying and powder coating.

Powder coating is also referred to as electrostatic spray painting and is the process of applying dry paint to a surface. Similar to the propellant/paint mix inside a can, compressed air is utilised to send atomised paint particles through a paint gun onto a target. The particles are so fine that they are like dust or powder. As with the aerosol can, the particles gain an electrical charge from the friction as they pass through the nozzle. The positive charge on the particles means they repel each other and distribute evenly when they hit the surface to be painted.

Industrial paint spraying is often done inside a specially designed booth with an air cleaning and extraction system to protect workers from breathing in harmful chemicals. For Spray booth filters, visit www.dustspares.co.uk/spray-booth-filters

Vacuum coating is a method used to apply water-based paints to surfaces. This is usually objects like plastic, wood or glass. The object is placed in a chamber where the whole object is submerged or nozzle sprayed. When the object is removed, it is exposed to high levels of UV light called curing, which dries the object in seconds.

Lastly, flatline spraying is the most commonly used method in industrial settings that need to paint in huge quantities. Items are placed on as assembly line and fed to a machine designed to paint that specific part. Spray guns are programmed with a sequence of movements so the whole object is coated evenly.

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