All you need to know about paint spray guns

How does a paint spray gun work in bodywork?

In bodywork, the spray gun is the central tool for applying primers, basecoats and Clearcoats to your car's bodywork. If you know how to use it properly, you'll not only be able to optimise the quality of the finish and apply the product correctly, but you'll also be able to reduce product losses and ensure that the work is regular and reproducible.

1. Operating principle :

The Spray gun is based on nebulisation: compressed air, supplied by the compressor, meets the product to be sprayed at the nozzle. This breaks up the flow of paint into micro-droplets, forming a homogenous spray that is deposited on the surface to be treated. Two main systems are used:

• Gravity: the cup is repositioned on top of the nozzle, and the paint falls by gravity towards the nozzle.
• Suction: the cup is placed underneath, and the paint is sucked up by vacuum.

2. The impact spanners on the paint gun :

A professional paint gun has three essential settings:

• Air pressure: this determines the size of the particles and the regularity of the spray. If the pressure is too high, the result is mist and a lack of charge.
• Product opening: adjusting the flow of paint delivered is crucial to avoid drips and lack of material.
• Spray pattern: allows you to change from a narrow cone (precise areas) to a wide fan (large surfaces)

It is adjustable and can be set according to use.

3. Technologies used :

In modern bodywork, two technologies dominate:

• HVLP (High Volume Low Pressure): large volume of air at low pressure, to limit misting and improve transfer (ideal for top-of-the-range Clearcoats and finishes).
• RP (Reduced Pressure): a compromise between high transfer and application speed, popular for fast drying bases.

4. The importance of maintaining your paint spray gun :

A high-performance spray gun requires rigorous maintenance:

• Thorough cleaning after each use, by removing the Nozzle, needle and air cap.
• Use clean filters to avoid impurities
• Regular checks on the condition of seals and wearing parts.

A poorly maintained Spray gun generates spraying defects (spitting, uneven spray pattern, dust inclusion) and increases the risk of rework.

5. A role in final quality :

In the car body shop, the paint spray gun is the tool that transforms a controlled mixture into a perfectly taut, even coat. Its precision, combined with the expertise of the professional bodybuilder, ensures :

• Uniform film thickness
• Optimum gloss
• Reduced defects such as orange peel, gaps and overcoating

Mastering the operation and settings of a spray gun means guaranteeing regular, effective and profitable bodywork.

Which paint spray gun should you choose for your bodywork?

For a bodywork workshop, the choice of spray gun should be based on the types of paint work to be carried out, the precision required and the productivity targeted.

1. Spray technology :

a) HVLP (High Volume Low Pressure)

• Advantages: excellent transfer rate, reduced misting, ideal for top-of-the-range Clearcoats and finishes.
• Disadvantages: slightly slower application speed, requires a high-performance compressor

b) RP/HTE (Reduced Pressure / High transfer efficiency)

• Advantages: combines high efficiency and fast application speed, very versatile (primer, base, Clearcoat)
• Disadvantage: transfer rate slightly lower than HVLP

2. Type of repair :

• Primers: prefer a paint gun with a wide Nozzle for fast coverage and correct loading
• Water-based or solvent-based paints: thin Nozzle for precise atomisation
• Clearcoat: HVLP or RP spray gun, offering excellent tension and optimum gloss.

3. Ergonomics and comfort :

• Balanced weight, comfortable handle to reduce fatigue during long stages of car repairs
• Flexible airflow and trigger for precise control
• Solvent-resistant materials for optimum durability

4. Professional brand of paint spray gun :

Professional workshops often prefer well-known brands such as Sata, Sagola, Devilbiss or Iwata. These brands offer consistent atomisation, readily available spare parts and compatibility with different paint products.

How do I get an even finish?

To achieve an even application and a better finish with a body paint spray gun, it's all about the balance between adjusting the spray pattern, the paint spray gun and preparing the car's surface.

1. Perfect preparation :

A poorly prepared surface is unforgivable, even with the use of a high-quality spray gun. Sanding must be fine and even to avoid visible marks under the paint. Cleaning and degreasing must be thorough, using suitable cleaners to remove dust, grease and residues.

2. Adjust the paint spray gun:

The pressure must be appropriate, generally between 2.0 and 2.5 bars for a Clearcoat or solvent base. It is important to have a constant flow of product, neither too weak nor too strong. The shape of the spray is also very important, and a regular, well-centred fan to cover the surface evenly will ensure an ideal repair.

Tech'team tip: To achieve an even finish, we recommend you test spray a pad before repainting the surface. This allows you to check the viscosity, pressure and uniformity of the spray.

How do I clean the paint spray gun?

Cleaning the spray gun is a crucial and essential step in ensuring the protection and durability of the tool. It helps maintain atomisation accuracy by preventing paint or Clearcoat residues from clogging the nozzles. It also prevents contamination and extends the tool's service life. Effective cleaning means that your paint spray guns will last longer.

We recommend that you clean immediately after application so that the paint doesn't dry out, because the more it sticks, the more complicated it will be to remove. Use a suitable Thinner to clean thoroughly.

Drain the product remaining in the cup, then rinse quickly. Then use the Thinner in the circuit to eliminate internal residues. Dismantling the parts (Nozzle, needle, air cap) is important for separate cleaning. Wait until they are completely dry before reassembling to avoid corrosion and deposits.

Where on your bodywork should you start painting?

In bodywork, you never start in the middle of the visible area. A professional always starts outside the part or on an overlap area to avoid overloading and starting marks. In practical terms, you start applying paint to a dismantled part (door, wing, bonnet) and begin spraying outside the surface, starting the spray in a vacuum, then gradually working your way into the part. Release the trigger on the way out, still outside the area to be painted. This technique allows you to:

• Obtain an even application from the first pass
• Avoid lumps or build-up of product at the beginning/end of the pass
• Maintain a constant thickness across the entire surface of the car.

It is advisable to apply the paint from left to right and with a precise movement to ensure even coverage of the car paint and the same spray distance from start to finish. This practice is necessary to ensure very high quality results on the vehicle. The drying time and number of coats of paint depend on the type used.

What are the criteria for choosing a paint spray gun?

The criteria for choosing a paint spray gun depend on a number of factors: technology, type of project, ergonomics, comfort and reliability. The choice of equipment depends on the Touch up you want to do to your surface.