Frank Colson on sat 25 jun 05
The concept of total wet firing, simply defined, is the process of placing a
undried (wet) clay form into a preheated firing chamber and removing the
piece a few minuets later, finished, glazed and all. This is going "beyond"
the raku process! True, it is primarily an experiential
experience which has more in the doing, than the production of a pot. As
such it is an exciting ,spontaneous, and rewarding way to conduct a
workshop group.
Some time ago, Gerry Williams did wet firing in which he suggested
formulating clay with one percent barium carb. However, it was a two
phase operation which necessitated bisque firing before glaze firing. It
ended up as a one and one-half hour development rather than
an eight to fifteen minute process I developed.
The composition of the clay, any clay, needs to be alerted to accept the
shock of placing into a preheated (1600 to 1900+F) kiln "wet".
Not bisqued! Whereas raku clays often use a coarse grog, wet fire clay uses
an expanded silica grain; 20 to 30 mesh. "Expanded" grain
is basically a silica grog which has been prefired to the maximum expansion
of each particle.
Like paper clay, which provides additional strength, wet fire clay has
ceramic fibers wedged into the clay body to withstand sudden heat..
Both the expanded grain and the fiber are impervious to thermal shock of
more than 2000 degrees F. Although the addition of fiber strands
make the clay short for working, it provides the mechanical strength
necessary to support a form through the transformation from wet into
its fired state. The key, here, is to add just enough grain and fiber to
maintain plasticity to the clay.
Glazing wet fire clay should be done by mixing dry powdered glaze with
sodium silicate, often called "water glass". The mixing of glaze and
sodium silicate needs to be made and applied onto the form just prior to
placement into the pre-heated kiln. The primary points to keep in
mind are that both the clay and glaze should be thoroughly wet, so much so,
that a quick misting water spray is applied to the form just as it is
placed into the kiln. This misting creates a protective "heat" barrier,
protecting the thick painted glaze application from spalling.
In fifteen minuets ,or less, the glaze will bubble and finally evolve into a
smooth covering.
Upon completion, the form may be handled as with raku, removing it from the
kiln and post firing for additional surface effects.
One word of caution at this stage, however, is that wet firing can result
in a very fragile piece of work. It is more likely than not, that only
the outside, and inside surface of the form have matured leaving a
"sandwich" of wet clay in-between. If the form has a small closed
opening, or neck, it is quite likely that the inside is still "raw" (wet
clay). If the form is open mouth, such as a bowl, there is better
likelihood
that all surfaces have matured.
On the onset of development of Total Wet Firing, ten class sessions were
conducted for 15 art teachers. Close to one hundred pieces of wet clay were
fired, all varying in shape, thickness, and glaze which resulted in the
successful completion of forms, ranging in size from a few inches to more
than a foot.
Frank Colson
www.R2D2u.com
| |
|
