What Causes Bubbles in Paint?
4 Answers
Bubbles in automotive paint can be caused by improper construction conditions and processes, such as oil stains, dust, sweat, or other contaminants on the surface being painted. These impurities can trap moisture, excessive temperature differences between the paint and the surface, improper use of thinner, or excessive addition of hardener. Causes of the phenomenon: Gas trapped within the coating breaks through the surface, forming bubbles that may burst or wear away, creating pinholes. When the surface of the coating dries slightly faster than the interior, and the internal solvent or air continues to evaporate after the surface has begun to set, bubbles may form as the gas breaks through the surface. Solutions: Use the appropriate amount of thinner and hardener, adjust the paint viscosity to the correct level, and control the spray thickness. Properly fill and sand the substrate to eliminate contamination. Adjust the air pressure appropriately to minimize air entrapment—typically, the pre-gun pressure gauge should be set at 0.2MPa. Improve the working environment by controlling temperature and humidity. Extend the recoating time to allow the lower layers to dry thoroughly. Let the mixed paint sit for 10 minutes before spraying. When using heat drying for the coating, control the standing time to allow solvents to fully evaporate before preheating the coating.
Paint bubbling is a pretty common issue, and I've encountered it several times when doing my own spray painting. The main causes are insufficient surface preparation, where residual moisture or grease gets trapped under the paint forming bubbles; or uneven paint mixing—stirring too fast introduces air, which then appears as bubbles when sprayed. Spray gun pressure that's too high can make the paint fly too aggressively and trap air, while pressure that's too low often leads to uneven application. High environmental humidity is a big headache—it slows paint drying, trapping moisture inside that can't escape, inevitably causing bubbles. I remember last time I painted my car, I got lazy with surface cleaning and ended up with tons of bubbles. I had to start over, sanding thoroughly to ensure dryness, then applying thin layers slowly to succeed. My usual advice: sand carefully before painting, wipe with cleaner, and wait until completely dry. Avoid rainy days—if painting indoors, use a fan for ventilation. If bubbles appear, don’t panic—let it dry, sand smooth with fine grit, and respray to save extra effort.
Paint bubbling is mostly caused by moisture. Once when I was painting furniture during a particularly humid period, the bubbles were outrageous. If there's any water left on the surface and not properly cleaned, the paint will bubble when it covers it; if air gets mixed in while stirring the paint, the result will be unsightly. Improper spray gun pressure can also cause issues—too much pressure will whip air into the paint. My advice is to always check the surface before painting—it must be dust-free and dry. Stir the paint slowly, don’t shake it vigorously. The best time to paint is during dry weather. If it’s rainy, wait it out or use a dehumidifier. Don’t rush the application—apply thin, even layers for the best results. If bubbles do appear, don’t rush to fix them. Let it dry first, then sand it down and patiently apply another coat. This job requires patience—careful work can save a lot of hassle.
The main causes of paint bubbling are unclean surfaces or residual moisture, along with improperly mixed paint introducing air. High environmental humidity slows paint drying, trapping moisture and causing bubbles. Incorrect spray gun pressure (too high or too low) can also lead to issues. My routine involves thoroughly cleaning surfaces and ensuring complete dryness before painting. I gently stir paint to minimize bubbles and use medium spray gun pressure for thin coats. In high humidity, I postpone work. If bubbles appear, I wait for drying, sand, and repaint.
