Vitrification
- , by Haley Stanaford
- 2 min reading time
Let’s talk vitrification. What is it? Vitrification refers to the clay reaching its maturity in the firing. This specifically has to deal with the amount of melt that happens.
Now, when I say melt, it isn’t exactly the melt you think of when talking about firing. Clays reaching their maturity is all about how much melt happens to try to seal the ceramic and make it less absorbent. But true, full vitrification is rare. In ceramics, when we say something is “vitrified”, we typically mean the most it can be vitrified, as we will not truly reach full vitrification. It makes more sense for us to use the words “reaching maturity” when talking about firing as it is more accurate.
Picking up a piece of bisqueware, you can feel how rough it is. You can also notice how porous the piece is and how it will soak up water easily. A cone 6 clay body, unglazed and fired to cone 6 will come out with a very different feel to it, smoother and won’t absorb as much. This happens because of the melting of fluxes in your clay body.
The piece on right is more vitrified while left is less. From digitalfire's page about vitrification
It is important that your clays get fired to maturity for a variety of reasons. The first being that under-fired pieces do not have the same strength as matured pieces. The second being that water absorption is no joke! Water absorption in ceramics refers to the amount of water that will get absorbed in the ceramic.
Lower water absorption in pieces will yield physically stronger work. Also, heating up any of your pieces that have water trapped in them, will cause them to break. The tests for water absorption and shrinkage are pretty simple tests and can be done in any studio. You can read more about testing water absorption and shrinkage tests here.
Haley Stanaford is currently a Post Baccalaureate student in ceramics at the University of Kansas where she is currently taking a Clay and Glaze Formulation taught by Colby Charpentier in addition to her studio practice. She also is a Sales Representative at Bracker’s Good Earth Clays in Lawrence, Kansas.
