• Dirty air cap and fluid tip (distorted spray pattern)
• Insufficient or incorrect overlapping of strokes
• Gun stroked to rapidly (dusting of the paint)
• Gun stroked at wrong angle to surface
• Stroking to far from surface
• Too much air pressure
• Split spray
  

Prevention

• Remove air cap and clean tip and air cap carefully
• Follow the previous stroke accurately. Deposit a wet coat.
• Avoid whipping. Make deliberate slow strokes
• Keep gun at right angle (perpendicular) to surface during stroke
•  Maintain 15-25 cm (conventional) or 35 –45 cm (airless) distance to surface
• Use least air pressure necessary
• Clean the fluid tip and air cap
  

Remedies

• Strip and clean or sand down and repaint