More from our upcoming online workshop, The Middle Glazes: The how, what and why of mid temperature glazes.
Delayed crazing-it’s a thing!
Our student Lois Aranow asked us if she was seeing things, because work she had that was originally not crazed, we’re now crazed, even though the firing was a long time ago.
To learn more about how crazing works, check out our youtube channel, https://youtu.be/NkNda1R-xrofor a video describing exactly what crazing is and why it happens. What you can and can’t do about it, and what are total myths.
A lot of you commented that the glazes in our last post were crazed. The main thing to note is that A) Crazing is based on the chemistry B) Crazing is always dependent on the exact clay body you are using. This is why some glazes craze on one body and not another.
These two images are exactly the same tile. The left tile was photographed after the glaze has been cool for about six hours. The right image is the exact same tile four days later.
As you can see, the glaze continued to craze, even though it was completely cool when we took the first picture. This is because crazing is caused by the stress of Thermal Expansion.
Every clay and glaze has its own thermal expansion. As they cool, they settle into their expansion and if the two are radically different, the glaze will crack to relative the stress.
In some cases it can take days, weeks months or even years for the stress to set abs and for the work craze.
There are a hundred myths out there, as how to fix crazing. 99% of those answers are myths and wrong. There is only one answer.
This is a chemistry problem and that is the solution.
Join us in our online classes and workshops to learn more.
8/22/2019 12:00:13 pm
Hi Matt Katz, I'm doing your Advancing Glazes Course now. In lecture 7 I get realy confused; I always have heard that the crazing of a glaze on a body is Glaze tension, due to a high C.T.E. of the glaze en a lower C.T.E. of the body. In your course you state that it is due to a Low C.T.E. of the glaze and a high C.T.E. of the body.
8/22/2019 09:22:23 pm
6/20/2022 09:08:08 am
I totally agree with your post.
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Matthew and Rose Katz - Founders of Ceramic Materials Workshop
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