Expert: Debra Flint - 9/17/2011

Question
We have recently discovered that our pieces are crazing weeks/months after they are completed.  We use Laguna EM210 While Low Fire clay which we fire to 04.  Our glaze is Duncan Pure Brilliance brush on glaze.  I have spoken to Duncan and Laguna and both agree that the two are compatible.  Laguna did recently adjust my firing up to 1950 from 1940 and added a hold at the end of my bisque fire to attempt to fix the problem.

My question is that we only glaze the sides and tops of our tiles (size range from 4 inches to 12 inch diameter)  Is it possible that the crazing is occurring because of moisture entering the rear of the piece? All of our pieces are show only and are no washed/used.  The reason I ask is we have one product that is glazed on all sides.  It is our smallest piece and we haven't noticed any crazing on these pieces.

Any help that you can provide would be very appreciated.

Answer
The glazing has nothing to do with the crazng. It is your firing that does the crazing. Your greenware firing most be a cone 04 if not you will get crazing.  Double check with a cone shelf sitter and make sure you are getting a correct firing. Good luck