How to Use a Paint Spray Gun – Complete Guide
Prepare Your Paint or Coating for Spraying
The first critical step in using a spray gun is to ensure that the your paint is properly prepared for the spraying process. In general, to use paint in a spray gun, paint cannot be too thin or too thick.
For airless or a pressure-fed spray gun, the paints can be used without needing as much thinner. However, for a gravity or suction-fed spray gun, the paints will have to be slightly thinner in consistency than most latex paints.
For best results, use a viscosity cup, like the Zahn 2-Cup, and verify that the paint runs between 20 and 30 seconds. This speed will typically spray well from any spray gun, but is most necessary for the gravity and suction-fed fun types.
Once verified that the paint is properly thinned for the spraying process, the next step should be ensuring that the product surface area has also been properly prepared.
Prepare the Product Surface
As important, if not more important, than having the paint prepared is having the product surface properly prepared. This is also referred to as anchor or etch pattern creation.
How the surface will be prepared depends on the type of paint or coating being used, the surface type that will be painted and many other variables.
Most coating will have a technical data sheet that shows how the surface should be prepared, like a NACE or SSPC callout. Either way, it is always a good general rule to ensure that the product surface is cleaned of any dust or oil prior to painting by using a solvent or thinner to wipe down the surface.
Select the Proper Fluid Tip and/or Air Cap
When using a spray gun that offers a variety of air caps and fluid nozzles, be sure to review the options available in order to select the best size suited for the paint. For most gravity spray guns, a fluid tip will allow the paint to flow when the trigger is pulled.
Once the gun has a tip large enough to allow the material to flow, next is ensuring that the tip allows control of the amount of paint effectively applied. This can require performing a few test patterns to see if the spray pattern and flow is comfortable for use.
Also refer to the spray gun manuals to have a better idea of the tip sizes that are most common for different materials.
Verify that your air cap is meant for the viscosity of paint being sprayed as some air caps are not designed to atomize heavier material. For more info on selecting a spray gun air cap, contact SurfacePrep to get assistance on choosing the right air cup and fluid nozzle.
Begin Adjusting Air Pressure
Once the coating is properly prepare and the spray gun nozzle and air cup are properly selected, the next step is to begin increasing air pressure until the paint break up performs as desired. If using an HVLP spray gun keep the pressure to the gun below the pressure listed on the spray gun cap. The pressure listed represents the maximum pressure that can be uses while still getting the paint waste reducing benefits of HVLP.
Increase the air pressure while doing test spray with the goal of achieving the proper amount of break up. Just remember that the smaller the paint particles appear, the better finish that will be achieved. However, it can be overdone and too small of particles will give a dry spray finish.
Use Good Technique
While painting, keep the spray gun about six to eight inches, or about a hand’s length, away from the product’s surface. Move the spray gun back and forth at an even pace. Overlap each pass by about 40%. Keep the spray gun perpendicular to the surface and avoid swinging the wrist. All of this will ensure a consistent spray technique and a good finish.
Evaluate Your Initial Results
It is a good idea to perform a check on how much paint is on the surface after a pass or two. This is helpful to ensure that the proper tip has been selected and that the air pressure is at the right speed to apply enough material. If the material runs while painting, that typically is a sign that the paint is too thin or that the tip is too large. On the flip side, if there is not enough paint than the tip may be too small or it may be time to consider using a pressure-fed spray gun or an airless paint sprayer.
Finish the Part
After this initial checklist has been completed and the spray gun is working as desired, paint away! Be sure and note the settings and spray gun details down for future reference. This information will help the process become easily repeatable if the same material is used again in the future.
Clean Your Spray Gun
After the job is complete, be sure to thoroughly clean the spray gun so that it will perform well the next time it is needed. Proper cleaning will involve:
- emptying all the paint from the spray gun
- running cleaner (solvent or water depending on paint type) through the spray gun until only cleaner is coming out
- ensure that the air cup is thoroughly cleaned as well
Store the spray gun in a safe place.