The 3 Main Factors that May Cause Dirty Paint Jobs

Vehicle wrapped in plastic sheeting in paint booth.

When it comes to painting, a solid prep job is key to setting yourself up for success. A perfect paint job is as much about the preparation as the application.
As much as we’d like to get the car in the booth as fast as possible, it’s worth taking a bit more time to focus on prepping for paint (and it may not be what you think). Successful preparation includes a thoughtful combination of masking, cleaning, and the removal of dust and other contaminants. Here are a few ways to help ensure clean paint jobs and some considerations you may not be thinking about today:

  • Hand wiping car panel with paper towel.

    Properly cleaning panels

    Contamination can happen every second a panel is in the shop. Dust is your paint job’s worst enemy. Even the finest of dust could show up in the final paint job and then what? Rework. Time wasted. Additional material use. Even the price of one oily fingerprint could result in a lot of work. Taking time to thoroughly clean has an added benefit – every time you clean, it’s one more time the panel is being checked for defects like pinholes and inline scratches.


    • Blow off the entire vehicle in between each step of the prep process. It’s highly recommended to use a vacuum sander and cleaning disc to help ensure there are no physical contaminants on your panels (i.e., sanding dust, pollen, hair, etc.). Blow off the panel, wipe with wax and grease remover, then blow off the substrate again, use tack cloth on the part (even on the section of the air hose that may touch the car), and then you can start spraying.
    • Use both solvent and water-based cleaners to help prevent chemical contamination resulting in fisheyes, delamination, and other chemical-related issues.
  • The inside of an empty paint spray booth.

    Booth cleanliness

    Every time a vehicle or a part is brought into the booth, or a painter enters, new contaminants can be introduced into the environment. Every second a painter has the spray gun trigger pulled they are creating overspray that can lead to contamination. Booth fans and filters capture some contaminants but some will likely still remain after the job is done. These recommendations can help improve results.


    • Limit sanding dust in the air from entering the paint booth by leaving the booth fans running when opening doors or bringing vehicles in or out. Although it may seem unreasonable to turn on an empty booth, the positive air pressure within will actually help prevent dust from coming in.
    • Sweep and vacuum booth walls and floors every morning with the booth running and in spray mode. This will trap dust and dirt in the filters instead of it settling on the walls and the floor.
    • Keep the number of supplies in the booth at a minimum. They could potentially contaminate the surface you just prepped or painted. Like with the panel or vehicle, supplies can get hit with overspray or collect contaminants.
  • Man spraying paint onto a side car.

    Painter attire and PPE

    Often difficult to admit but ultimately the hard truth, nearly every dirt nib comes from either the painter or an improperly cleaned panel. No matter how clean the painter thinks their clothes are, they are still full of contaminants that could affect the paint job. Using the proper personal protective equipment (PPE) not only protects the painter from the chemicals but also protects the paint job from the painter who may bring outside contaminants in.


    • Always wear paint suits in the booth, along with the proper gloves and respirator or even better, a fresh air supply.
    • Don’t use the same gloves you wore to prep for painting. Grab a new pair before you spray. A new pair of gloves is a minimal cost compared to the amount of potential rework.
  • Flaws in the preparation process can cause issues for the painter, disrupt booth cycles, and inevitably affect the shop’s efficiency and production. Investing in an experienced painter can be extremely beneficial for shops but consider looking at the steps before the booth that may make all the difference.

    A clean vehicle benefits a shop from start to finish for a variety of reasons. A few extra minutes spent cleaning could help save hours in the end. After all, there is no successful paint job without the proper prep.

    Written by Jason Garfoot, Senior Application Engineer, 3M Automotive Aftermarket Division