The so-called boils or bubbles, also called needle points, are small superficial pitting produced by breakage or deformation of the paint surface, generated by the escape of occluded solvent once the outer surface of the paint layer has dried.
The reasons why it happens are the following:
- Solvents too fast.
- High ambient temperature.
- layers too thick
Solutions to avoid it:
- Use a slower solvent with balanced evaporation.
- Give lighter coats with longer flash-off intervals.
Reparation:
- Unfortunately the boils are produced from below and the only option to eliminate them is to remove the layer of varnish where the defect occurred and reapply.