What Chemical Changes Happen When Pottery Is Fired in a Kiln?

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When pottery is fired in a kiln, a few very interesting chemical changes take place. Learn about what chemical changes take place when pottery is fired in a kiln with help from a ceramic artist and instructor in this free video clip.

Part of the Video Series: Making Pottery
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Video Transcript

Hi. I'm Beth Fleischer, and today we're going to go over what chemical changes happen when pottery is fired in a kiln. The actual drying of your pottery doesn't happen outside of the kiln, even though it seems dry and it's considered bone dry, it needs to be further dried inside the kiln. The first stage is the atmospheric drying and that drives out every last bit of moisture from the atmosphere that's in your piece of clay. The next step is called dehydration and this is where chemically combined water inside your clay is driven off. This is not the same as atmospheric water. So at this point the clay actually changes and it can no longer be reconstituted into clay. A chemical change has occurred. The next stage is called burn off and this where things such as sulfates and carbon are burned out of the clay. The next stage is called quartz inversion. In this stage the quartz crystals rearrange themselves inside your clay and the clay actually swells a little bit. This stage it's really important to go through very slowly. Most programmable kilns do this for you. The last stage of the chemical process of the clay in your kiln is the vitrification. It'll take you from this to this. That's the chemical process that happens in the kiln. I'm Beth, thanks for watching.


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