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
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.
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.
Copyright 2006 Brad Walker. All rights