Trapped Air

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What are the common faults in greenware?

Trapped Air

Air trapped in the walls of pieces. When a pot is fired the first action of the kiln's heat is to drive off the water in the clay. If the clay has air trapped in it, the air pocket can fill with steam. As steam is heated it expands, and if the kiln gains temperature fast enough the steam can build up enough pressure to blow out the wall of the pot. Clay straight from the bag can usually be assumed to be free of air pockets, but reworked clay needs to be wedged to eliminate air. When joining or adding clay to a form, we need to be careful not to trap air in the joints. Also, thick walls tend to hide air pockets and trap the moisture needed to cause disaster. Thin and light is the way to go. If your pot explodes it can destroy other's work also!

   

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