Blistering or Pinholes

Bubbles form during fusion and remain in the decoration.  Usually a result of air, water, dust, or lint being left under the decal film when fired.


Fine Blistering

Sign of either too fast a preheat burn-off or trapped organic carbon entrained in the color film due to poor ventilation.


Crawling

The contraction of an ink film into dots.  This is a sign of low surface tension on the piece of ware usually caused by grease, oils, or dirt on the ware surface prior to application of the decal.  May also be caused by a ruptured color film from a crease in the decal or excessive stretching during application.


Matte/Grainy Finish

A result of under firing (temperature of the kiln is too low); if the decal is undisturbed and has a powdery appearance, re-firing at a higher temperature usually saves the job.

Dull Color

If decal appears exceptionally smooth and flat and soaked into the glaze, it is probably a result of over-firing.  Over loading and poor kiln ventilation will also cause color fade/dull colors.


"Ghosting"/Hazing

An undesirable cloudiness on the ware or in transparent areas may be caused by impurities in the decal soak water or poor ventilation during firing.  Low temperature glass firing usually does leave a slight haze where the decal cover coat had been; this can be easily wiped away with a damp cloth.

Pitting

A small depression in the surface of the decoration, perhaps caused by tiny bubbles in the glaze, or if a sharp rough spot is present, perhaps caused by spalling fire brick.


Splitting

Caused by the use of creased decals or excessive stretching during application.