How to Reduce Overspray in a Paint Booth

Q: How can my shop reduce overspray in our paint booth?

A: Overspray occurs when a spray coating lands on an unintended surface. Although this may be unavoidable during the painting process, technicians should be aware of certain best practices. By following proper spraying techniques and spray booth maintenance, painters can reduce the amount of overspray while painting.

Why reducing overspray is important

When overspray reaches unintended areas, it can lead to problems with lighting and filters in the paint booth, as well as paint defects on the surface to be painted.

When filters become clogged, their performance and airflow can be affected. For example, filters may not bring clean air into the cabin and dirty air out of the cabin as well as if they were clean. Dirty filters can also cause higher concentrations of fumes, airborne particles and contamination, making them a dangerous environment for painters as well as an ideal one for the paint itself. Shops can also lose a lot of money over time because clogged filters require more frequent replacements.

Lighting is extremely important in the painting process, especially for color matching. Having the best bulbs installed doesn’t matter much if they’re covered in overspray. This can affect cabin lighting and therefore coloring inside the cabin, causing metamerism.

During the actual painting process, overspray due to improper spraying can cause paint defects, such as unwanted dirt, dry spray and the like. Some flaws can be spotted immediately, while others won’t be noticed until after a coating has dried. Either way, paint defects can lead to bottlenecks in production due to the need to redo a paint job.

What are the best spraying techniques?

Every technician should know and follow these best spraying techniques to help reduce overspray. Of course, we all know that application between certain paint lines varies widely, but follow your product application method from training. Before spraying, make sure the spray gun is at the optimum distance from the surface to be painted, which, depending on the gun and whether you are spraying water or solvent, can vary from 6 to 10″.

Also, the tip of the spray gun should remain perpendicular to the surface at all times. Anything at the wrong angle can result in more overspray outward of the panel than desired and darker areas where the nozzle is closer to the panel due to tilt. Fixing this on its own can help save the “halo” in blends. It is common for many beginning painters to have problems in their mixtures due to application issues. Improper gun mixing and “dry” mixes lead to poor repairs and costly rework.

Find the right spray pressure

The correct spray pressure is also important when trying to reduce overspray. Low pressure can result in a thick, peeling orange finish, as well as the possibility of over application of the coating. High pressure can result in streaking, dry spray or over atomization of paint and lots of paint everywhere. The correct pressure level will result in an even coating and coverage with no visible flaws.

To achieve the correct spray pressure, technicians must consider their gun configuration, tip size, and coating temperature. We recommend that you always check your materials data sheet (TDS) to see what the recommended settings are for your gun and perform a test spray on a low setting to get an idea of ​​the spray gun and its coverage. From there, slowly increase the pressure over time until even coverage is achieved.

Pro tip: Always set the pressure to the wall about 5 psi more than you want. Keep the spray gun as wide open as possible at the gun itself so you don’t choke the gun and take advantage of all the CFM (cubic feet per minute) coming to the gun.

Keep the spray gun clean

The spray gun itself is key to reducing overspray because a technician cannot get the right one finish if their spray gun is dirty. The spray tip can clog over time and cause an uneven coating. We’ve all seen when a gun sprays more to one side or the other. It is imperative to keep the gun and all air passages clean.

The hose can also be covered in overspray and these same hoses tend to break down over time. Don’t forget to change your cabin hoses once a year, and if you use a fresh air system, make sure you have a wicking hose for your breathing line.

Ironically, overspray can also build up on spray guns and therefore needs to be disassembled and cleaned regularly.

Improved spray booth configuration to reduce overspray

Downward airflow is best for producing cleaner paint jobs and reducing overspray due to its top-down direction. Once the clean air comes from the top of the cabin, it flows directly into the filters in the floor. For this reason, technicians must work from top to bottom to follow the airflow in the cabin.

Cross-draft and semi-vented booths are more prone to overspray since their airflow moves from side to side. In a cross cabin, it is best to paint against the booth airflow and spray starting closest to the filters at one end of the booth. This will ensure that the overspray lands in the wet paint you sprayed and not on a dry surface you are about to paint. Wet surface will allow overspray to melt resulting in much less “dust” on the surface.

How Paint Booth Maintenance Affects Overspray

It is important to perform paint booth maintenance as this can play a direct role in reducing overspray. An air make-up unit and exhaust fan parts have a huge impact on the amount of overspray that remains in a booth’s cabin. Running routine diagnostic checks can help catch problems early or even prevent major equipment failure issues. Cleaning the AMU and exhaust fan will ensure they are at peak performance and working as they should.

The best way to reduce overspray

To ensure your shop is following the best ways to reduce overspray, start with your paint booth setup. Invest in a downdraft cabin if possible and track its maintenance, including make-up air units, exhaust fans, filters, and lighting. From there, train technicians in spraying techniques to reduce overspray and in cleaning spray guns.