Heather Pedersen on sun 24 jan 10
I am working with small flat pieces about 1/8 inch thick [3mm] and
about 1 inch [25mm] in diameter out of southern ice porcelain. I have
previously once fired them in a normal cone ten glaze firing my studio
does, but have recently obtained a small kiln to run some additional
experiments.
One of the results I am curious about is how fast may I fire these
super small, super uniform and super thin pieces? I just started my
first test bisque at 400F/hr to 1720F, and then 108F/hr to 1828F
loaded with a single layer of pieces on the bottom of the kiln. The
kiln is a Paragon Xpress Q11A (a tiny little thing that fits nicely on
my kitchen counter).
Has anyone else experimented with this, or has experiences to share?
Regards,
Heather Pedersen
Heather Pedersen on mon 25 jan 10
Hi Chris,
Thank you for your concern. I hope I can ease your nervousness a bit.
My kitchen has a breakfast bar that extends out into the middle of our
kitchen/living room/dining room area, putting it several feet from the
nearest wall.
One of the reasons I particularly selected a kitchen outlet is because
here there is a legal requirement for the small appliance outlets in
the kitchen and the bathroom to be on their own (GFCI'd) circuit,
which I verified on our electrical panel. So I simply removed
everything else from the outlets while firing. Having the GFCI
protection is a nice bonus.
The large size of the room I was in, and the open door should have
provided sufficient ventilation for the 2.5 oz (~1/8 lb) of porcelain
I was firing.
For the glaze firing, and for any metal clay (which I am hoping to get
a chance to try out to complement my porcelain jewelry), I plan to put
the kiln outside on our (metal) balcony table. I am uncertain about
the circuit on my exterior outlet (may be part of the HOA with unknown
other loads), so I may have to get an extension cord to take it back
to the kitchen outlet (Since this is a small 115V kiln, cords less
then 20ft long, and larger then 12 gauge are acceptable per the
manual, although I think I would make it 14ga, since that's what its
own cord is)
Best regards,
Heather Pedersen
On Mon, Jan 25, 2010 at 8:16 AM, Chris Campbell w=
=3D
rote:
>> a tiny little thing that fits nicely on
> my kitchen counter
>
>
> I don't know the answer to your
> question but this sentence makes
> me a bit nervous.
>
> I have to question the safety of
> locating a kiln on your kitchen counter.
>
> Other than the fact that it requires
> its own dedicated circuit, it also needs
> to be placed 12" away from any wall.
>
> Depending on what you are firing, it
> could emit some fumes that you might
> not want to taste in your food.
>
> I may be wrong or overly cautious, but
> I would move it to another spot.
>
> Chris Campbell - in North Carolina
>
> VOTE! VOTE! VOTE!
> for three new PC Board Members.
>
> =3DA0Chris Campbell
> President - Potters Council
>
> www.ccpottery.com
> http://neriagechris.blogspot.com/
>
Chris Campbell on mon 25 jan 10
> a tiny little thing that fits nicely on
my kitchen counter
I don't know the answer to your
question but this sentence makes
me a bit nervous.
I have to question the safety of
locating a kiln on your kitchen counter.
Other than the fact that it requires
its own dedicated circuit, it also needs
to be placed 12" away from any wall.
Depending on what you are firing, it
could emit some fumes that you might
not want to taste in your food.
I may be wrong or overly cautious, but
I would move it to another spot.
Chris Campbell - in North Carolina
VOTE! VOTE! VOTE!
for three new PC Board Members.
Chris Campbell
President - Potters Council
www.ccpottery.com
http://neriagechris.blogspot.com/
Rimas VisGirda on tue 26 jan 10
Chris, re a dedicated cicuit. I have a great test kiln about 8x8x8 in. inte=
rior that fires to c/10 on 110v, fires fast too. I think it's an AIM (too l=
azy to trek through the snow to the studio to check). I wouldn't worry abou=
t firing porcelain in my kitchen. Lusters, wax, decals, (oil based) overgla=
zes are another matter... How about firing in the bathroom, turning on the =
bathroom exhaust vent and shutting the door? Hope there's at least 2 bathro=
oms in the house...
Re the how fast part -I think the pieces the person is talking about can be=
fired as fast as the kiln will go. But that's just me... -Rimas
Vince Pitelka on tue 26 jan 10
In the commercial tile industry, some tile fired in rolling hearth kilns
goes from room temperature greenware to maturity and back to room
temperature fired tile in a total elapsed time of fifteen minutes. Don't
try this at home.
- Vince
Vince Pitelka
Appalachian Center for Craft
Tennessee Tech University
vpitelka@dtccom.net; wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka
Rimas VisGirda on tue 26 jan 10
Heather, in my experience there's only 3 temperatures that need care in spe=
=3D
ed of heating and those all depend on the nature of the piece being fired.=
=3D
=3D0A=3D0ABoiling point of H2O: All the physical water (moisture) within th=
e cl=3D
ay needs to be gone when the piece gets to 212F. Even if a piece "feels" dr=
=3D
y it still has moisture in it, "dryness" just means that the moisture in th=
=3D
e clay has reached an equilibrium with the humidity (water) in the air. My =
=3D
work sometimes gets into the range of being 1/2 inch thick; I wait until th=
=3D
e piece "feeels" dry, take my kiln up to 200F and hold there for 1 hr, then=
=3D
I go as fast as the kiln is capable to bisque, for me cone 05. For a 1/2 i=
=3D
nch wall 1 hr at 180F is sufficient time for the H2O to migrate out of the =
=3D
clay. In your case, small pieces 1/8 in thick, it would take no time at all=
=3D
and I would not do any kind of hold below 212F.=3D0A=3D0AChemical water: C=
hemi=3D
cal water -the water that's tied to the clay molecule (al2o3-sio2-6h20 -"si=
=3D
mple formula") gets released somewhere around low red heat (800-1000F, arou=
=3D
nd 1000F all the chemical h2o is gone... The chenmical water is released gr=
=3D
adually and generally migrates through the open-porous nature of the clay a=
=3D
t that stage. I have blown some sculptures, early on to my surprise, at tha=
=3D
t stage but they were around 2 inches thick AND I boosted the kiln (turned =
=3D
up the burners in a gas kiln) around low red heat. Later, I fired similar s=
=3D
culptures 2-3 inches thick but WITHOUT adjusting any rate of climb through =
=3D
that point and they bisqued just fine. My theory is that the sudden increas=
=3D
e in rate caused a sudden increase in released water into channels that wer=
=3D
e already full of water migrating out and the INCREASE is what caused the e=
=3D
vent. In general my rate of climb is about 300-400F/hr. But that's just me.=
=3D
..=3D0A=3D0AQuartz inversion: Quartz (silica/flint) changes size at a very =
prec=3D
ise temperature 1064F. This is only a problem for very tight vitreous ware =
=3D
and ONLY on the way DOWN for a typical glaze firing; on the way up the clay=
=3D
is at a bisque state and easily absorbs the shock (that's what makes Ameri=
=3D
can raku possible). On the way down, however, if the ware is vitrified and =
=3D
one area is hotter at 1064F than another, the brittle crystalline nature of=
=3D
the clay can't take the stress and will crack. HOWEVER, I have never exper=
=3D
ienced this happening in a glaze firing for any kind of shapes or sizes of =
=3D
ware. Refires are (for some reason) another matter and care must be taken b=
=3D
oth on the UP as well as DOWN -that's because the ware is already vitrified=
=3D
on the way up this time. HOWEVER, once again, I only loose large flat item=
=3D
s, plates and tiles, on refiring. For refiring my largeer plates and tiles,=
=3D
I slow my kiln down to 30F/hr between 1055-1070F then proceed at my normal
rate. My normal rate on both sides of quartz inversion is 400-500F/hr -use=
=3D
d to be 900F/hr but most (electric) kilns can't climb that fast and some co=
=3D
ntrollers have a problem with the number 9, plus I'm getting cautious in my=
=3D
old age? The typical quartz inversion crack is usually around the middle a=
=3D
nd the 2 pieces seem to fit back together perfectly with barely a hairline =
=3D
visible...=3D0A=3D0AThe preceding comes from personal observation and bias =
and =3D
works for me. Looking for the quartz inversion temperature, being too lazy =
=3D
to trek through the snow to the studio, I googled quartz inversion and foun=
=3D
d a page that has some nice general information -a few abiguities but gener=
=3D
ally clear, concise and accurate. the keyword being generally...=3D0A=3D0Ah=
ttp:=3D
//www.lakesidepottery.com/HTML%20Text/Tips/Clay%20drying%20and%20firing%20p=
=3D
rocess.htm=3D0A=3D0AAlso a nice color chart:=3D0A=3D0Ahttp://www.lakesidepo=
ttery.co=3D
m/HTML%20Text/Tips/Tempruturerange.htm=3D0A=3D0ARegards, -Rimas=3D0A=3D0A--=
- On Tue=3D
, 1/26/10, Heather Pedersen wrote:=3D0ARimas,=3D0A=3D0=
AI had=3D
been planning to gradually ramp up my speed, but I could jump=3D0Astraight=
t=3D
o the end to see if it's a problem or not. I think you're=3D0Aright, but it=
i=3D
s still a bit nerve wracking.=3D0A=3D0AGood idea on the bathroom.=3DA0 Unfo=
rtunat=3D
ely I only have one very small bathroom.=3D0A=3D0ARegards,=3D0AHeather Pede=
rsen=3D
=3D0A=3D0AOn Tue, Jan 26, 2010 at 5:08 AM, Rimas VisGirda m> w=3D
rote:=3D0A=3D0A> Chris, re a dedicated cicuit. I have a great test kiln abo=
ut 8=3D
x8x8 in. interior that fires to c/10 on 110v, fires fast too. I think it's =
=3D
an AIM (too lazy to trek through the snow to the studio to check). I wouldn=
=3D
't worry about firing porcelain in my kitchen. Lusters, wax, decals, (oil b=
=3D
ased) overglazes are another matter... How about firing in the bathroom, tu=
=3D
rning on the bathroom exhaust vent and shutting the door? Hope there's at l=
=3D
east 2 bathrooms in the house...=3D0A> Re the how fast part -I think the pi=
ec=3D
es the person is talking about can be fired as fast as the kiln will go. Bu=
=3D
t that's just me... -Rimas=3D0A>=3D0A
Lee Love on tue 26 jan 10
I could fire very fast in my modern wood kilns in Mashiko, after a
couple hour drying out period (I'd get to red heat in less than an
hour. ) I could hit cone 10 in 5 or 6 hours. If I glazed everything
and didn't mind it looking like a gas firing it would work. I'd fire
for 18 to 24 hours to get ash and flashing.
I think the important time of the firing is the end, when it
is good to soak for a little while.
--
Lee, a Mashiko potter in Minneapolis
http://mashikopots.blogspot.com/
"Ta tIr na n-=3DF3g ar chul an tI=3D97tIr dlainn trina ch=3DE9ile"=3D97tha=
t is, "T=3D
he
land of eternal youth is behind the house, a beautiful land fluent
within itself." -- John O'Donohue
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