How to Use Conventional Spray-gun Systems

There are several types of conventional spray systems. The low-pressure system uses a gun attached to the pot directly, and is used for smaller jobs requiring high degree of control.

The high pressure system pressurizes the paint and the air, and consists of a large pot, and hoses for the air and paint. This system is used for larger areas.

Both systems depend on a pressurized air supply from a compressor. The air is mixed with the paint at the orifice and atomises to create a fine even mist. Therefore, conventional spray systems are mainly used for solvent-based paints requiring a high quality fine finish.

Set --Up procedure

Attach the materials hose to the pot and tighten using a spanner.

Attach the materials hose to the spray-gun, then attach the air hose. Tighten both using a spanner

The amount of air can be adjusted by turning the air flow valve in or out.

The amount of paint can be controlled by adjusting the fluid control screw.

The fan control screw adjusts the fan width and pattern.

Pour the paint into the pot. Measure and add solvent to thin the paint according to manufacturers directions.Mix thoroughly

Secure the pot lid and tighten by hand.

Attach the air hose from the compressor to the pot. Adjust the regulator to the desired pressure. This is usually about 45 -60 psi.

Application Procedure

Use the correct respirator filter for the product.

Apply the paint using an even side-to-side motion. The gun should be kept at an even distance from the surface at all times, and the spray-gun should be kept moving the entire time. Overlap each stroke by 50%.

The air-cap can be adjusted to direct the spray-pattern vertically, or horizontally. This is done by simply twisting the cap.

Regularly check the finish to ensure the paint is being applied evenly and sufficiently.

Application techniques

It is better to build up the coating with several coats than to apply one heavy coat. Insufficient movement of the gun will result in a high build up of paint, leading to sagging and runs.

The gun should be maintained at a constant distance from the surface, and the spray pattern should be an even, slightly oval shape.

Pull the trigger just before the spray-gun passes over the surface, and release it after a full pass of the surface. Do not start or stop half-way across the surface. Keep the gun moving at all times.

Clean-up procedures

On completion of the work, release the pressure on the pot. You should be able to see the pressure drop by checking the regulator guage. Once the pressure is released, open the pot lid.
Pour the excess paint back into a suitable container.

Clean the pot using a compatible solvent. Spray solvent through the gun until it sprays clear.

Clean the air cap and remove the needle. Once the needle has been cleaned replace it. All paint should be cleaned carefully from the gun to ensure trouble-free service. However, do not immerse the gun in solvent.

To find out more about conventional spray-gun systems and for courses and training see painters.edu.au/Training-Courses/