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The Cracked Kiln Shelf

A standard cordierite or mullite kiln shelf can withstand rapid changes in temperature without cracking due to thermal shock.  Aside from a mishap such as dropping the shelf on a hard surface, shelves are difficult to crack.

But it can be done.  The most common way to crack a shelf is to fire it with a moisture containing object in contact with the shelf.  To avoid this kind of cracking, there are several tips to keep in mind.

1.  Avoid firing a kiln shelf that hasn't been dried sufficiently after applying kiln wash.  Not only can this cause the kiln wash to stick to the glass, it can also make cracking more likely.

2.  Prop plaster/silica molds (such as for casting) on kiln furniture so that the molds don't come into contact with the shelf. 

3.  If you're using kiln bricks or other kiln furniture that have been stored in a damp environment, pre-fire them to drive off the moisture contained the brick.  (Or place them on a warm kiln before using them inside the kiln.) Damp kiln bricks are notorious for causing cracked shelves.

Click here for more, including what to do if the shelf develops a crack.

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Copyright 2006 Brad Walker.  All rights reserved.

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Copyright 2005-2006 by M. Bradley Walker.  All rights reserved.

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