Why Does Paint Have Bubbles?
2 Answers
The causes of bubbling are as follows: 1. Exposure to sunlight or hot weather: Paint or water-based paint applied outdoors is often exposed to direct sunlight, causing the surface to heat up and eventually bubble. It may also be due to high temperatures in the production line, causing workers to sweat excessively during operation. Sweat droplets may fall onto the painted parts, and after cleaning between paint applications, small amounts of salt residue remain on the surface. When covered with paint film, the salt absorbs moisture in hot weather, and when exposed to heat again, the moisture expands outward, repeatedly pushing the paint film to form small bubbles. 2. Poor quality: The substrate being painted is of poor quality, such as having a high moisture content, which can cause the paint surface to become damp and bubble during use. 3. Incorrect painting: Not following the correct painting procedures, such as applying paint before the putty is dry. After painting, inadequate waterproofing measures, such as exposing the freshly dried paint to a humid environment or direct rain, can also cause bubbling. 4. Insufficiently dry construction tools: For example, compressors or air hoses may contain too much moisture, or water may come into contact with the paint surface during the construction process.
Every time I encounter the issue of paint bubbling, it reminds me of my experience repairing my own car during the rainy summer season a few years ago. The most common problem is inadequate surface cleaning, leaving behind oil stains, dust, or fingerprints on the car body. When painting, these impurities get trapped, preventing moisture from escaping and causing bubbles. High humidity is another culprit—excess moisture in the air gets absorbed into the paint film during application. Additionally, moving the spray gun too quickly or holding the nozzle too close can trap air; incorrect thinner ratios make the paint too thin or bubbly; or applying a second coat before the primer fully dries. Prevention requires attention to detail: thoroughly wipe the surface with alcohol before painting, then dry it with an air pump; choose a dry, well-ventilated environment; spray slowly and evenly, applying thin layers multiple times instead of thick coats. For repairs, the only solution is patiently sanding down the bubbled areas, thoroughly cleaning them, and reapplying primer and topcoat—otherwise, the paint may peel and lead to rust. The entire process is time-consuming but worthwhile, as small bubbles can escalate into major issues.