Jennifer F Boyer on fri 19 jan 01
Are the firing times of these 2 exactly the same? Or does old
faithful fire slower?
Jennifer
>
> My question is, (and I'll use a perrenial favorite glaze, floating blue
> as an example,) how is it that a nice brandy new tighty wighty kiln
> makes for awful icky pinholed nasty a** glazes, while the ancient,
> decrepit, forlorn and oft-abused dinosaur offers up perfectly smoothed
> pots from it's gap-rimmed maw? My assumption is that because it's a
> smaller kiln and with all these gaps it would cool faster, thus
> theoretically not giving ther glazes time to smooth over. On the other
> hand, I use an envirovent with the skutt, so perhaps that is causing it
> to cool faster? But how much faster? I'll have to run some tests with
> the vent off when no one will be around. Have I answered my own
> questions?
~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*
Jennifer Boyer mailto:jboyer@adelphia.net
Thistle Hill Pottery
95 Powder Horn Glen Rd
Montpelier, VT 05602 USA
802-223-8926
http://www.thistlehillpottery.com/
Check out this searchable sites about web hoaxes:
http://urbanlegends.about.com/science/urbanlegends/library/blhoax.htm
~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*
michael wendt on fri 19 jan 01
Diane,
I think you should compare the two kilns for things like rate of heating and
venting. I do a blue ^10 that hates fast rise rates. I think the glaze melts
before all the gassing has stopped if I fire it too fast. If the kiln cools
quickly after the glaze melts, that does not affect it at all. I fire gas so
venting is less an issue compared to electrics, but your little loose kiln
is effectively better vented than the big one and venting can play a role in
the finish both because it slows the rate of rise and because it provides
oxygen to burn out organics in the glaze or in the worst case in the body.
Slow the rate you fire. Worth a try?
Also, a leaking lid or a fan forced vent on a kiln can pull cool air through
the cone sitter, changing the cone value dramatically, so I always shut the
vent off after the temperature is reached where organics are burned off
(Ceramic Science for the Potter lists 700 deg C as the top temp) so I fire
to 1000 degrees C to be safe before shutting off. To be sure, use a
pyrometer and plot the temperature rise and fall with respect to time for
each kiln.
Regards,
Michael Wendt wendtpot@lewiston.com
Diane wrote:
My question is, (and I'll use a perennial favorite glaze, floating blue
as an example,) how is it that a nice brandy new tighty wighty kiln
makes for awful icky pinholed nasty a** glazes, while the ancient,
decrepit, forlorn and oft-abused dinosaur offers up perfectly smoothed
pots from it's gap-rimmed maw? My assumption is that because it's a
smaller kiln and with all these gaps it would cool faster, thus
theoretically not giving ther glazes time to smooth over. On the other
hand, I use an envirovent with the skutt, so perhaps that is causing it
to cool faster? But how much faster? I'll have to run some tests with
the vent off when no one will be around. Have I answered my own
questions?
Diane in Ct,
John Hesselberth on fri 19 jan 01
Diane G. Echlin wrote:
> On the other
>hand, I use an envirovent with the skutt, so perhaps that is causing it
>to cool faster? But how much faster? I'll have to run some tests with
>the vent off when no one will be around. Have I answered my own
>questions?
I think you've done a splendid job of answering your own question. Does
your Paragon have thicker walls? If it is really ancient it might. Your
envirovent could be substantially increasing the cooling rate. You can
turn it off for cooling without worrying about fumes. If it is the kind
that has the fan right under the kiln you might have to worry about
whether the fan wiring is bothered by the heat though. Of course since
your Skutt is computer controled, the easy experiment to run is to fire
it down. Add a ramp that tells it to go to 1500 deg F at 150 deg F per
hours.
Do you really stuff the Paragon full and load the Skutt lightly? That
could also affect cooling rate. It also sounds as if you may not be
firing to the same peak temperature (cone). Checking that is easier by
putting cone packs in the kiln.
I think what I've learned over the years is that properly firing an
electric kiln takes just as much care as properly firing a gas kiln.
Only with gas you just about have to learn to do it. The electric kilns
are simple enough that we can just turn the switches on and let them go.
But that will not give us the best results.
Regards, John
"The life so short, the craft so long to learn." Hippocrates, 5th cent.
B.C.
Cindy Strnad on fri 19 jan 01
Hi, Diane.
The Envirnovent will cause your kiln to cool a lot faster. And really, by
the time you get to the cooling cycle, I don't see your glazes putting out
much in the way of fumes. It's on the way up that they're dangerous.
**Someone correct me if I'm wrong, please.**
At any rate, I think you'd be safe, with most glazes, to turn off the vent
fan when you get to around 1900 degrees F. I say 1900, because in a recent
post, John H. said you should start your slow cooling by around that
temperature, and I trust him. You might give it a try, and see if it
improves your Floating Blue results.
Cindy Strnad
Earthen Vessels Pottery
RR 1, Box 51
Custer, SD 57730
USA
earthenv@gwtc.net
http://www.earthenvesselssd.com
Cindy Strnad on fri 19 jan 01
Hi, Diane.
Another thought . . . Floating Blue is very sensitive to temperature, isn't
it? So I've heard, anyhow. Are you certain the two kilns are firing to the
same temp? Unless you're double-checking with shelf cones, it's hard to
tell, and they probably aren't. Just something else to consider.
Cindy Strnad
Earthen Vessels Pottery
RR 1, Box 51
Custer, SD 57730
USA
earthenv@gwtc.net
http://www.earthenvesselssd.com
Diane G. Echlin on fri 19 jan 01
John Hesselberth wrote:
> > Hi Diane,
> > It is probably more than just the temperature to which you fired. If you
> want the results to be the same you have to match the cooling rates.
> Heating rates must also be similar, but they are usually not as much of a
> problem as cooling rates.
>
> Regards, John
>
Hi John,
Okay, I am really beginning to grasp the whole rate of cooling issue,
and it really makes a lot of sense to me, but the way my kilns act in
light of this discussion makes no sense at all. My so-called "little"
kiln is an ancient crumbling 2-ring paragon with elements that are
probably older than I am. There are chunks missing from many of the
bricks, and this baby *breathes* when it fires. My big kiln is a
relatively new Skutt KM 1027 with the controller, with the 2 1/2 bricks
(I think--the thinner ones at any rate), has new elements, and is tight
as a kiln gets, I think.
My question is, (and I'll use a perrenial favorite glaze, floating blue
as an example,) how is it that a nice brandy new tighty wighty kiln
makes for awful icky pinholed nasty a** glazes, while the ancient,
decrepit, forlorn and oft-abused dinosaur offers up perfectly smoothed
pots from it's gap-rimmed maw? My assumption is that because it's a
smaller kiln and with all these gaps it would cool faster, thus
theoretically not giving ther glazes time to smooth over. On the other
hand, I use an envirovent with the skutt, so perhaps that is causing it
to cool faster? But how much faster? I'll have to run some tests with
the vent off when no one will be around. Have I answered my own
questions?
Diane in Ct, muddled, befuddle, and because of the cold, behuddled.
PS: I know all the danged pitfalls of floating blue, but inevitably it's
nearly perfect in the little kiln and gawd-awful in the big kiln....
Diane G. Echlin on fri 19 jan 01
Wow, thanks for all the insights, folks! It never occurred to me to
shut the vent off during cool down in a glaze firing! Also, as a side
note to John's question, I pack the kilns fairly loosely for both bisque
and glaze firings. For some reason, I've never really seen the sense
in overloading to the brim. Must be a patience issue, too! And yes, I
use witness cones in both kilns!
Diane in CT
Diane G. Echlin on sat 20 jan 01
Little old kiln fires about 65-75 minutes slower. But from recent
discussion it seems that the cool-down is what's crucial. Or is that
only for reduction firing?
Diane in CT
Jennifer F Boyer wrote:
>
> Are the firing times of these 2 exactly the same? Or does old
> faithful fire slower?
> Jennifer
>
> >
> > My question is, (and I'll use a perrenial favorite glaze, floating blue
> > as an example,) how is it that a nice brandy new tighty wighty kiln
> > makes for awful icky pinholed nasty a** glazes, while the ancient,
> > decrepit, forlorn and oft-abused dinosaur offers up perfectly smoothed
> > pots from it's gap-rimmed maw? My assumption is that because it's a
> > smaller kiln and with all these gaps it would cool faster, thus
> > theoretically not giving ther glazes time to smooth over. On the other
> > hand, I use an envirovent with the skutt, so perhaps that is causing it
> > to cool faster? But how much faster? I'll have to run some tests with
> > the vent off when no one will be around. Have I answered my own
> > questions?
>
> ~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*
> Jennifer Boyer mailto:jboyer@adelphia.net
> Thistle Hill Pottery
> 95 Powder Horn Glen Rd
> Montpelier, VT 05602 USA
> 802-223-8926
> http://www.thistlehillpottery.com/
>
> Check out this searchable sites about web hoaxes:
> http://urbanlegends.about.com/science/urbanlegends/library/blhoax.htm
> ~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*
>
> ______________________________________________________________________________
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
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>
> Moderator of the list is Mel Jacobson who may be reached at melpots@pclink.com.
Cindy Strnad on mon 22 jan 01
Hi, Priscilla.
Get yourself a box of self-standing shelf cones in ^6 and try them out with
one of your firings. If they don't bend, you may want to try ^7 bars or
mini-cones. Yes, they're available. I use them whenever I do a load in my
little old kiln--which I do from time to time. It's handy at times because
it's small.
Cindy Strnad
Earthen Vessels Pottery
RR 1, Box 51
Custer, SD 57730
USA
earthenv@gwtc.net
http://www.earthenvesselssd.com
Priscilla Wilson and/or Janice Lymburner on mon 22 jan 01
I'm wondering after reading some of the posts in this series if I should
start buying cone 7s (is there such an animal?) for my kiln sitter. I'm
firing stoneware slip to cone 6, and everything seems to be going fine...
but now I wonder if I've unknowingly only been firing to cone 5. My glazes
are cone 5, so it's just the clay body I'm concerned about. Seems fine, but
I'm not experienced enough to thump it and know for sure! My (first and
only) kiln is an old electric one; I've only fired it about 20 times. Thanks
for any advice offered.
Priscilla in sunny Sautee, Georgia
-----Original Message-----
From: Diane G. Echlin
To: CLAYART@LSV.CERAMICS.ORG
Date: Saturday, January 20, 2001 12:00 AM
Subject: Re: Firing kilns comparatively (was ^6 glaze)
>Wow, thanks for all the insights, folks! It never occurred to me to
>shut the vent off during cool down in a glaze firing! Also, as a side
>note to John's question, I pack the kilns fairly loosely for both bisque
>and glaze firings. For some reason, I've never really seen the sense
>in overloading to the brim. Must be a patience issue, too! And yes, I
>use witness cones in both kilns!
>Diane in CT
>
>___________________________________________________________________________
___
>Send postings to clayart@lsv.ceramics.org
>
>You may look at the archives for the list or change your subscription
>settings from http://www.ceramics.org/clayart/
>
>Moderator of the list is Mel Jacobson who may be reached at
melpots@pclink.com.
John Hesselberth on mon 22 jan 01
Priscilla Wilson and/or Janice Lymburner wrote:
>I'm wondering after reading some of the posts in this series if I should
>start buying cone 7s (is there such an animal?) for my kiln sitter. I'm
>firing stoneware slip to cone 6, and everything seems to be going fine...
>but now I wonder if I've unknowingly only been firing to cone 5. My glazes
>are cone 5, so it's just the clay body I'm concerned about. Seems fine, =
but
>I'm not experienced enough to thump it and know for sure! My (first and
>only) kiln is an old electric one; I've only fired it about 20 times. =
Thanks
>for any advice offered.
>Priscilla in sunny Sautee, Georgia
Hi Priscilla,
If you really want to be firing to cone 6, putting a small cone 7 in =
your Kiln Sitter=AE (note to Jonathon--mine is a Sitter, not a =
Setter. It says so right on the label) will probably be closer than =
what you are currently doing. But the only way to really know is to =
place a pack of large cones in your kiln and see how they fall.
You may not need to fire any higher though. Is your clay vitrified =
to your satisfaction? Are your slips giving you the look you want? =
I assume you are not using glaze and are making decorative rather =
than functional pieces. If so, and you are getting what you want, =
you may not need to change anything.
Regards, John
P.S. Yes, cone 7s are available + lots and lots of others.
"The life so short, the craft so long to learn." Hippocrates, 5th =
cent. B.C.
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