White spots 0.3–0.5 mm (0.01–0.02 inches) in diameter surrounded by denser spots (blister-like white spots) appear.
Cause:
This may occur if a solid image is printed on coated paper, if a solid image is printed during duplex printing, or if printing is done at low temperature.
Solution:
If these white spots appear, check for insufficient toner fusing. (Insufficient Toner Fusing)