Glaze Course - Lesson Summaries
Glaze Defects - Crawling, Shivering and Pinholing
Lesson Number 25
Often fired pots when removed from the kiln will have flaws of various kinds. These can be as slight as a little more or less gloss than anticipated or as great as the entire glaze coating peeling off.

In between these extremes are many cases that may be considered technical faults but which, in some circumstances may be desirable.

Crazing, a common feature in many soft, feldspathic glazes, is referred to as "crackle" when it is acceptable. This issue was discussed at length in Lessons 22 - 24

Pinholing and crawling are accepted as part of the shino aesthetic while blistering on a gross scale is the basis of crater glazes.

So a large part of defining what are glaze "defects" is really a question of attitude.

Over the next couple of lessons we will look at the following "issues" that might or might not, in respect to your glaze aesthetics, be defined as a defect. We will also look at ways in which these "defects" might be at least controlled and perhaps eradicated if that is your desire.

  • crawling
  • peeling or shivering
  • pinholing
  • blistering and cratering
  • excessive gloss
  • running
  • bloating
  • excessive dryness or mattness
  • color defects.

In this lesson we will:

  • define the effects usually considered defects in a fired glaze.
  • suggest ways in which glaze defects might be minimised or eradicated.

Full lessons contain content and activities not listed above. More lessons will be added to this list as they are completed.
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Contact: Lawrence Ewing - 1015 Ellis Rd, Five Rivers, RD3, Lumsden, Northern Southland,
New Zealand