Expert: Sam Kelly - 6/18/2009

Question
QUESTION: I have a set of very old (50 yrs) Mexican dishes.  They are terra cotta and
glazed.  They were fine in Az but since living in FL, I have a problem!  They
must have tiny cracks all over the glaze because they mold sitting in the
cabinet.  I am trying to figure out how to seal them and still be able to use
them for food.  The easiest would be to dip with hi-fire clear glaze, but to
what cone is my old terra cotta safe?  Your help is appreciated, I hate to pitch
this beautiful set of handmade dishes.

ANSWER: Hi cathy, unfortunately the firing temp they were done at would be a guess.I would say low fire, maybe 1100degC. Whats happened is they have absorbed moisture and the body has expanded minutley enough to crack(craze) the glaze.
What you could do is fire one of the plates as it is to 1100degC in an electric kiln ans see what happens.

Sam

---------- FOLLOW-UP ----------

QUESTION: Sam, so 1100degC will let me know how the terra cotta clay body will behave at
that temp. Are you thinking it will also re-melt my glaze and possibly fill in the
crazing?  How is crazing dealt with?  Do you usually re-coat with a clear glaze?
Thanks so much for your expertise!

Answer
Hi Kathy, it can do a number of things, one being blow to pieces, or absolutly do nothing. One step at a time.
Re glazing onto your cracked unknown glaze is also unknown in what it will do.
Fire one just like it is to 1100degC and cross your fingers.

Sam