Glaze Course - Lesson Summaries
Glaze Defects - Cratering, bloating, running etc.
Lesson Number 26
In the last section on glaze flaws we discussed

  • crazing
  • crawling
  • peeling or shivering
  • pinholing

Many glaze defects can be countered by adjusting the balance of oxides that end up in the glaze melt.

There are other faults that might look as though they are glaze defects but that are in fact problems with the clay body. One of these is the effect called bloating.

Blistering and cratering is an effect that results from the release of gas from the glaze, a process that occurs with all glaze melts but becomes a problem if the gas is still being released when the kiln is shut down. Crater glazes are those developed specifically to take advantage of textural effects that can result from glazes especially designed to be releasing gas at the shut down.

Quality issues of excessive gloss, running or mattness are usually the results of glazes in which the balance of flux to stabilizer and glass former need adjustment in relation to the temperature that the kiln is fired to.

In this lesson we will look at:

  • bloating
  • blistering and cratering
  • dunting
  • devitrification
  • excessive gloss, dryness or mattness
  • running

Full lessons contain content and activities not listed above. More lessons will be added to this list as they are completed.
Next Lesson

Contact: Lawrence Ewing - 1015 Ellis Rd, Five Rivers, RD3, Lumsden, Northern Southland,
New Zealand