Glaze Course - Lesson Summaries
Glaze Defects - Crazing Part 3
Lesson Number 24
Over the years of assisting ceramic students at Otago Polytechnic I have come to realise just how difficult it can be to really control the degree and patterns of crazing in the infinite number of glazes that are used and experimented with by potters.

Quite often the initial decisions made to change a glaze so that it will e.g. craze less, are something of an intuitive guess based on previous experience. That is fine if you have previous experience but many of us do not so how should we start?

It is an unfortunate fact that the information given to us by the researchers who produced the tables of Oxide Expansion Factors is non-specific and may not be a reliable guide when it comes to the particular glaze we wish to change. So when we put our glaze into Matrix and it gives us a C.O.E. the implication is that if we lower the C.O.E. we will always move towards less crazing.

Regrettably this is not the case. Each crazing problem has to be treated as a unique case. More often than not strategies that worked for one glaze previously may not work for another. The process can be long and frustrating particularly where we wish to preserve the unque character of the original glaze.

Despite these problems craze issues can be solved in many glazes particularly where the glaze is already close to fitting the body.

In this lesson we will:

  • further discuss limitations associated with the use of the coefficient of expansion as a guide to controlling crazing.
  • look again at strategies for tackling the task of reducing crazing in glazes.
  • work through a more complex craze reduction problem using Matrix
  • look at ways in which we can utilize the decorative potential of crazing.

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