Emily Lees on sat 12 aug 06
I have bisqued a wall piece which consists of a slightly concave base to
which I added textured slabs. The piece has been successfully bisqued, but
someone in the studio where I rent tapped it and suggested that it might
have some air trapped under one of the slab additions. It is designed to be
fired flat. If there is air, is the piece in danger of exploding in the gas
kiln? Would it just crack, or will pieces land on other ware in the kiln? We
fire to cone 9. It is a communal kiln, and I don't have any control over the
firing. I am willing to risk losing the piece due to cracking, but I don't
want to risk damaging other work (mine and others'). Any advice is welcome.
Lynn Goodman Porcelain Pottery on sat 12 aug 06
If it made it through the bisque, it's probably fine. As long as the
kiln isn't fired really quickly, any moisture from glazing (moisture
trapped in clay walls and air bubbles, then quickly expanding in size
when it turns into steam, is what causes pieces to blow up, not the air
bubbles themselves) will be driven off before it can cause problems.
Just curious--I have never heard of tapping pieces to hear if they have
air bubbles. Is this an actual thing or just someone being an "expert"?
Lynn
On Aug 12, 2006, at 2:55 PM, Emily Lees wrote:
> I have bisqued a wall piece which consists of a slightly concave base
> to
> which I added textured slabs. The piece has been successfully bisqued,
> but
> someone in the studio where I rent tapped it and suggested that it
> might
> have some air trapped under one of the slab additions. It is designed
> to be
> fired flat. If there is air, is the piece in danger of exploding in
> the gas
> kiln? Would it just crack, or will pieces land on other ware in the
> kiln? We
> fire to cone 9. It is a communal kiln, and I don't have any control
> over the
> firing. I am willing to risk losing the piece due to cracking, but I
> don't
> want to risk damaging other work (mine and others'). Any advice is
> welcome.
>
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Lynn Goodman
Fine Porcelain Pottery
548 Court St.
Brooklyn, NY 11231
718-858-6920
Cell 347-526-9805
www.lynngoodmanporcelain.com
Paul Lewing on sun 13 aug 06
On Aug 12, 2006, at 11:55 AM, Emily Lees wrote:
If there is air, is the piece in danger of exploding in the gas
kiln? Would it just crack, or will pieces land on other ware in the
kiln?
That's one of the most persistent ceramics myths going, and it's been
going for as long as I've been doing clay, at least. Air pockets do
not explode in the firing. It's water turning to steam that
explodes. Don't worry about bisqued clay at all. Especially the
first ten years or so that I made pots, before I bought pugged and
bagged clay, I mixed clay in a dough mixer, and didn't have a pug
mill. Even though I wedged it, I had a lot of air bubbles in a lot
of pots. I've seen pot that were broken after the glaze firing that
had air pockets big enough to stick the tip of your little finger in,
and they'd survived just fine.
Paul Lewing
www.paullewingtile.com
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