Warm Glass website

Information from the archives of the Warm Glass website and bulletin board.

Tips by Date                          Tips by Category    

Warm Glass website

WG Bulletin Board

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.


Copyright 2006 Brad Walker.  All rights reserved.

Click here to sign up to receive daily updates for the Warm Tips website.  These updates will come via email and will alert you as new tips are posted.


Got a tip to pass along?

Or a tip you'd like to see?

Four Corners International, Inc.

4140 Clemmons Road, #320

Clemmons, NC  27012   USA

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

Designed, implemented, and published by Four Corners International, Inc.