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. While this may be inevitable during the painting process, there are some best practices for technicians to know. By following good spraying techniques and paint booth maintenance, painters can reduce the amount of overspray while painting.

Why reducing overspray matters

When overspray gets onto unintended areas, it can cause issues with lighting and filters within the paint booth, as well as paint defects on the surface being painted.

When filters become clogged, their performance and airflow can be affected. For example, filters may not bring clean air into the booth and dirty air out of the cabin as well as if they were clean. Unclean filters can also cause higher concentrations of vapors, airborne particulate, and contamination, making it an unsafe environment for painters as well as unideal for painting itself. Shops can also lose a lot of money over time, as congested filters require replacements more frequently.

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 the booth’s lighting and, therefore, the coloring within the cabin, causing metamerism. 

During the actual painting process, overspray from improper spraying can cause paint defects, such as unwanted dirt, dry spray, and others. Some defects can be spotted right away, while others won’t be noticed until after a coating has dried. Either way, paint defects can cause bottlenecks in production due to having 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 some paint lines varies greatly but sticking to your product’s application method from training needs to be followed. Before spraying, make sure the spray gun is at the optimal distance away from the surface being painted, which, depending on the gun and whether you’re spraying water or solvent, can vary from 6-10".

Also, the spray gun tip should remain perpendicular to the surface at all times. Anything at the wrong angle can result in more overspray than wanted outward of the panel and darker areas where the nozzle is closer to the panel due to the tilt. Correcting this by itself can help save “haloing” in blends. It’s common for many newer painters to have issues in their blends due to application problems. Improper blending with the gun and blends being “dry” causes poor repairs and costly redoes.

Finding the correct spray pressure

The correct spray pressure is also important when trying to reduce overspray. Having low pressure can result in a thick and orange peeled finish, as well as the possibility of over-application of the coating. Having high pressure can result in streaks, dry spray, or over-atomization of the paint and a lot of paint going everywhere. The correct pressure level will result in an even coating and coverage with no visible defects.

To get the right spray pressure, technicians must consider their gun setup, nozzle size, and coating temperature. We recommend always checking your materials technical data sheet (TDS) to see what recommended settings are for your gun and performing a spray test on a low setting to get a feel of the spray gun and its coverage. From there, slowly increase the pressure over time until an even coverage is achieved.

Pro Tip: Always set the pressure at the wall about 5 psi higher than wanted. Keep the spray gun set as wide open as possible at the gun itself to not choke the gun down and take advantage of all the CFM (cubic feet per minute) coming to the gun.

Keeping the spray gun clean

The spray gun itself is vital to reducing overspray, as a technician cannot achieve the right finish if their spray gun is unclean. The spray nozzle can become clogged over time and cause an uneven coating. We’ve all seen when a gun is spraying more on one side or the other. It’s imperative to keep the gun and all air passages clean.

The hose can also become covered in overspray and those same hoses tend to break down over time. Remember to change your booth hoses once a year, and if you are using a fresh air system, be sure you have a non-wicking hose for your breathing airline.

Ironically, overspray can also build up on spray guns and therefore should be taken apart and have all parts regularly cleaned.

Best paint booth setup to reduce overspray

Downdraft airflows are best at producing cleaner paint jobs and reducing overspray due to their top-down airflow direction. After clean air comes from the top of the booth, it flows directly down into the floor filters. For this reason, technicians should work from high to low to follow the airflow within the booth.

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

How paint booth maintenance affects overspray

It’s important to perform paint booth maintenance upkeep, as it can play a direct role in reducing overspray. Both an air makeup unit and exhaust fan parts greatly impact the amount of overspray that stays within a booth’s cabin. Performing routine diagnostic checks can help catch problems early on or even prevent big equipment failure issues from occurring. Cleaning the AMU and exhaust fan will ensure they are at peak performance and working as they should.

Best way to reduce overspray

To ensure your shop is following the best ways to reduce overspray, start with your paint booth set up. Invest in a downdraft booth if possible and keep up with its maintenance, including air makeup units, exhaust fans, filters, and lighting. From there, train technicians on overspray-reducing spray techniques and spray gun cleaning.