How a spray gun can ruin your paint job: part I.

After the process of repairing damage to a component of the bodywork, it is time to coat the surface with finishing paint. This is one of the most rewarding times for paint shop professionals, which is why spray guns are their most precious asset. However, a spray gun can also ruin your paint job if it’s not in good shape, so today we are going to analyze a first part of them to prevent that from happening. Are you ready? Let’s go!

What is a spray gun?

An airbrush spray gun is a tool used to coat different surfaces and substrates through a process of atomization of the primer or finishing paint. Atomization is obtained by making the paint interact in one way or another, usually by mixing, with a certain air pressure.

With this, the drop of paint is broken into tiny fractions so that they are deposited on the work area in an orderly manner and in sufficient quantity to obtain a final layer of great surface homogeneity and with sufficient thickness. The guns are made up of the components that we see in the following image:

The function and the main features of these components are the following:

• Cup or deposit. It is the component in charge of storing the paint that is used to paint the surface. It is located at the top (gravity gun) or bottom (suction gun) and has a capacity of 600 or 200 ml. The new paint preparation systems for gravity spray guns are made up of a rigid cup and a flexible one placed inside that facilitates to the application of the lower parts of the vehicle or with the gun in an inverted position.
• Air flow regulators. They allow the air pressure in the gun to be adjusted to meet the requirements of the manufacturer and the type of gun. They generally have a regulator at the gun inlet and another on the body of the gun. To guarantee the most reliable working pressure possible and eliminate pressure drops, it is necessary to place a manometer at the gun inlet or use a nozzle one.
• Trigger. It is the trigger element of the gun and has two positions. The first only lets air out, while the second allows air and paint to come out together to generate atomization.
• Needle and fluid tip. They are the elements that control the amount of product that will reach the work piece. To this end, the needle moves inside the orifice of the fluid nozzle in order to allow the passage of paint to a greater or lesser extent. There are different diameters to adapt to the viscosity of the paint used (primer, clear coat, etc.).
• Product flow regulator. It allows regulating the amount of product that will come out of the nozzle thanks to the fact that it moves the needle in the fluid tip.
• Nozzle. Directs the compressed air flow towards the product flow to obtain atomization and spray pattern. It is consistent with the size of the fluid tip and the needle.
• Fan regulator. Controls the shape of the spray pattern to adjust it to the type of application required (open or closed areas).
• Compression gland assembly. It is the mechanism that seals the passage of the needle through the body of the gun. This element is self-adjusting to extend the life of the gun.

Poor condition of any of these elements in a spray gun can ruin your paint job, so the utmost care is required when handling them and storing the tool after use.

Nozzles, fluid tips and needles used

Of all the components analyzed in the previous point, the nozzle, fluid tip and needle are the ones that must be adjusted for the viscosity of the product that is going to be used. That is why, in the daily operation of the workshop there are these two options in this regard:

• Use a single spray gun that has different sizes of tips, needles and fluid tips, with the aim of mounting on each occasion the one that best suits. As is evident, during the repair process products with different viscosities are used, so with this system there is no choice but to make continuous changes, with the loss of time that this entails and the risk of damaging said components during handling, which can definitely ruin your paint job.
• Have three spray guns, each with the proper size nozzle, fluid tip and needle for the paint or group of paints being worked with. Generally, this is the option chosen by workshop professionals, so they have a gun for primer work, one for the application of the two coat and another for the clear coat.

Whichever option is chosen, what is evident and essential is that, before introducing the product or paint into the gun cup, make sure that the fluid tip is the right size for the viscosity of the product used and that the needle and nozzle are consistent with it. If not, there is a high risk that the spray gun could ruin your paint job. The following table shows the most common ones for gravity guns, which are the most common in car refinish bodyshops:

Ok, and that’s it for part one of how a spray gun can ruin your paint job. Do not miss our second analysis soon where we will see other aspects that can also lead to this fatal outcome.