You've already received good advice, yet I thought I would just
chime in with one more aspect concerning your re-glaze question.
Marvin was right on the money when talking about re-firing clay
work that already has a previously fired coat of glaze. Even so,
I get the feeling that you probably are talking about a low-fire
clay formula that may have been decorated with an "underglaze"
or stain, but didn't have a clear OVER-glaze on it when it
actually went through the glaze firing cycle.
Well, there are two things to consider about that situation...
both of which will make a difference as to how well a fresh coat
of liquid glaze will stick when applied to it. First, if you are
firing only low-fire materials, then it is very likely that that
particular clay piece is still very porous after firing. It's
just the nature of low fire clays to stay fairly porous until
they reach MUCH higher temperatures... underglazes will act
primarily in the same way. This is a good thing in your
situation, for your student's piece has probably still stayed
fairly porous and should reasonably accept a good coat of glaze.
The second consideration is that, since there is no previously
fired coat of glaze to create a barrier, then a fresh coat of
liquid glaze be able to readily reach the clay's surface and
take hold. It would be different, however, if the surface of the
clay was already sealed with a previously fired coat of glaze.
Such a case would require a little extra attention... as Marvin
so adequately explained!
My only further suggestion is that you be sure to use a fairly
standard firing schedule when you fire that piece again... one
that doesn't allow the temperature rate to climb unusually fast.
The re-firing of that piece shouldn't give you any problems
unless it already shows signs of undue structural stress after
the previous firing. And while we're on the subject of
structural stress, here's an important little tip that might
Most people starting out in clay (in fact, a surprising amount
of clay artists at ALL levels) simply don't pay enough attention
to the BASICS of hand building and throwing technique. Truth is,
the MAJORITY of clay work defects finally showing up after they
come out of the kiln are actually setup during the initial
construction and subsequent drying stages.
For that reason, the very best way you can help your students
avoid damage and defect to their prized clay work is to give
them the best construction and drying tips right from the very
beginning. Of course, most well formulated classroom clay will
be reasonably forgiving and hold together (even when some pretty
shaky construction techniques are involved!). However, just
using a few simple tricks can remove a good 93.5% of problems
from ever showing up (... baring unfortunate judgment errors in
firing, of course).
If you really want some of the best advice and easiest to use
information out there on electric kiln firing and avoiding clay
and glaze defects, then you want to get the collection at
www.ArtTeacherCeramicCenter.com. This stuff was written
especially for art teachers, comes VERY highly praised and
really gives us everything we need to know. (NOTE: DON'T go to
the regular site pages. Go instead to this address:
www.ArtTeacherCeramicCenter.com/special.html. It's a secret
offer page where you can get the whole collection for under $20
right now!... regular price is $33.87.)
Hope this helps, Becky. This forum has great folks giving good
advice, so feel free to ask if you have anymore questions.
(Although I'd say you won't have to ask many more after having
the stuff at that web address!) Good luck!
Tim in Charlotte
On Monday, February 05, 2007, at 11:48AM, "Rebecca Burch"
>I am REALLY new to ceramics but am really enjoying teaching and
>learning along with my students.
>So here's my question -- if a student has a piece that has
>glaze-fired, and she forgot to use the clear glaze on top, can
>re-glaze it and then glaze fire it again?