Paul Raymond on wed 17 sep 03
"Also, I just test fired my kiln for the second time and it went well. =
It =3D
seemed to go fine although it was very fast. I reached cone 06 in just =
=3D
under 12 hours, including candling. This is fast, Right? I am expecting =
=3D
it to be a few hours longer when I fire my first actual load. Any =3D
thoughts?"
Kathie-
Below is the schedule that I programmed. Maybe I don't quite understand =
it. Am I reading it correctly? As I see it this is setting a temp =
increase for 70 degrees /hour with no hold time. That would mean that =
after 3 hours the kiln would be at 210 degrees F. Is that enough =
candling time? I remember holding a gas kiln at about 190-200 F to work =
out the chemically combined H2O. We would use a mirror, too. It was a =
while ago, maybe I'm nor remembering the time frames well after 5 years. =
I began this firing at night thinking it would candle for several hours =
but around 6 the next morning (7 hours or so later) I was surprised to =
find the kiln reading about 1100 degrees. ( F )
When I learned how to fire the gas kiln we would candle glaze loads =
over night, at least 6 hours. And then start checking fro the Water =
Vapor. Once we were sure it was gone then away we went. Are the two =
types of kilns just so different that even generalizations about firing =
will not hold true from one to the other?=20
Any thoughts would be appreciated, thank!
Paul Raymond
Tenn.
Les' Perfect Bisque Schedule.
Seg Rate (Per hr.) Temp. (Target) Hold
1 70 deg 210 deg 0
2 240 " 450 " 0
3 120 " 600 " 0
4 240 " 950 " 0
5 120 " 1400 " 0
6 180 " 1915 " 00:20
7 9999 1888 " 00:40
Snail Scott on thu 18 sep 03
At 08:14 PM 9/17/03 -0500, you wrote:
>...after 3 hours the kiln would be at 210 degrees F. Is that enough
candling time? I remember holding a gas kiln at about 190-200 F to work out
the chemically combined H2O.=20
Three hours is plenty for most pottery of typical thickness.
I'd only go longer for much thicker stuff. (And 200=BAF won't=20
drive out the chemical water, just the physical; that happens=20
at higher temperatures.) Even for my rather thick sculpture,=20
(3/4" in places) two hours at about 150=BA-180=BAF is enough.=20
(If the clay were very dense and smooth like porcelain, AND=20
that thick, then I'd candle longer.)
>When I learned how to fire the gas kiln we would candle glaze loads over
night, at least 6 hours.
This is nearly always overkill. I used to do this, too, when=20
I fired institutional kilns, but it wasn't because it needed=20
six hours of candling. It was because it was hard to be there=20
overnight to tend, and if did your candling overnight, it=20
saved you a few hours of firing time the next day, and could=20
make the difference between shutting the kiln down in time=20
for dinner (or at least a sane bedtime), or not. And since=20
those institutional kilns were usually fired constantly, an=20
earlier shutdown time meant an earlier (and cooler) unloading=20
on the following afternoon, and a looser time frame for=20
reloading and candling the next load that night.
-Snail
=20
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