Blisters

Blisters is a common enamel defect, which is characterized by appearance of circular holes & bubbles in a cooled enameled surface.

May occur as a group, cluster or line of blisters.

Blisters are typically caused by gas evolution during firing, as a consequence of :

  • Poor steel quality
  • Scratches or damage on base steel
  • Large welding seams
  • Insufficient cleaning
  • Over pickling
  • Over blasting
  • Impurities in enamel
  • Too thick enamel film
  • Too high viscous frits
  • Contamination of furnace atmosphere
  • Under firing