William Brouillard on fri 7 jun 96
My experience with bisquing stoneware or earthenware in electric
kilns is that the ("smoke") or gases given off are linked to
impurities in the clay. Carbonacious material and sulfur componds
are present in most iron bearing clays and when heated to bisque
temperature will cause smoke and gas to be given off.
Even if you have not had a problem in the past you have to remember
that clay as it comes from the earth can vary in its composition.
Even small changes in composition can cause results like the ones
described in the earlier post. Red earthenware clays are full of
all kinds of stuff and most of them will give off fumes and smoke when
bisque fired. Stoneware and ball clays may do the same. Cedar Heights
stoneware is an example of a clay that will smoke during the bisque.
There is nothing wrong with the clay and the bisque fire does drive
off or eliminate gases that would cause glaze faults. Most potters that
do majolica style work will bisque their pots as hot as possible
to eliminate the outgasing problem.
There are some things that you could try to reduce or manage your
problem.
1. Check all of the wiring on your kiln exterior. Look for darkened
or melted wires or plugs. Repair or replace bad or damaged componants.
2.Vent your kiln during the bisue firing by leving some peeps open
or drilling a few small holes in the lid. If you clay is producing smoke and gas
3.Install an adequate venting system to remove the fumes that are produced.
A fan in the window will not do the job.
4. Make sure that you have a good supply of fresh air going into the
space that contains the kiln. The fresh air supply is called make up air
and is need to replace what ever is taken out of the room by the
venting fan. ( like trying to keep the bathtub full with the drain
plug out and the faucets on full blast)
5. Try other clay bodies to see if you can find one that is easier on the
nose.
The alumina content of your kiln wash is not the problem. Alumina is a very
refractory material and will not smoke or decompose at bisque temperatures.
Iron bearing clays(not white) and wax from glazing are the bad boys that like to
smoke. The more packed the kiln is the more pronounced the problem.
All that I can think of now.
Still raining here in the forest city
--
william brouillard
1011 literary road
cleveland,oh.44113
ch151@cleveland.freenet.edu
| |
|
