Cliff/Karen Sandlin on sun 6 oct 02
Hi =96 I just opened my scutt kiln with automatic controller at 240
degrees. My kiln has only been fired 31 times (04 bisque, cone 5 and
cone 6) and is 2 yrs. old. I bisqued this load to Cone 03 at SLOW
speed. I glazed by brushing on mostly layered Opulence and some
Spectrum glazes (that I have used before) on Highwater Redstone, Desert
Buff, and Laguna 50 and B-Mix clays. I set the controller to Cone 6,
SLOW speed, with a 30 min. hold. =20
=20
I had bisqued bits of clay holding large cone 6=92s and placed them =
about
on various shelves. My ware was about =BD=94 apart. =20
=20
According to the skutt manual, I propped the lid till 1000 degrees, then
closed the lid and always keep the top peephole unplugged.
=20
Some of my pieces have craters. Some have bumps. Some of the Opulence
glazes that have been matt finishes in the past are very shiny. NONE OF
THE CONE 6=92s bent all the way down. The cones on the top and bottom
shelves are totally upright; on the middle two shelves, they are bent
very slightly. I do the slow speed and the 30 min. hold to minimize
cratering.
=20
Is it possible that:
=20
1. I open the kiln too soon at 240 degrees? What temperature does
everyone else open a glaze kiln?=20
2. my ware is too close together? (nothing ever touches)=20
3. I use too much water when I throw?=20
4. I should not fire so many different clays or glazes in one load?
=20
Does anyone have any suggestions I might try? My glaze notes indicate
that a cone 5 firing with a 30 min. hold at slow speed resulted in no
craters, but the Opulence people told me their glazes should fire at a
=93good cone 6=94 or even a =937=94.
=20
Why would my cones not bend all the way down? When I last checked the
temp on my kiln it was at 2165, although I got busy and forgot to check
at the very end to see if it reached 2199. After 14.5 hours (including
the 30 min. hold), it was at 2035.
=20
I will really appreciate any help or suggestions.
=20
Thanks. Karen
=20
Chris Schafale on sun 6 oct 02
Hi Karen,
First, my sympathy on the disappointing firing -- been there, and it
stinks. Just a few thoughts about why. Overall, it definitely sounds
as if the work is overfired -- craters, bumps, and too-shiny glazes
all point that way.
> I had bisqued bits of clay holding large cone 6=92s and placed them abou=
t
> on various shelves.
Do you mean that you bisqued the cones, along with their holders,
before the glaze firing?? This is a bad idea. Cones that have been
fired before will not give an accurate reading the second time
around. Normally, you set your cones in a small amount of plastic
clay, puncture it a zillion times with a needle tool so it won't blow
up, and fire away. Let the cone holders get to bone dry before
firing if you want to be 100% sure they won't blow. Vince has a
great description of making cone packs in the archives, and also in
his book, if I remember right.
My ware was about =BD=94 apart.
This should be no problem. Many times, I pack ware closer than
this -- 1/4" apart is my rule of thumb.
> Some of my pieces have craters. Some have bumps. Some of the Opulence
> glazes that have been matt finishes in the past are very shiny. NONE OF
> THE CONE 6=92s bent all the way down. The cones on the top and bottom
> shelves are totally upright; on the middle two shelves, they are bent
> very slightly. I do the slow speed and the 30 min. hold to minimize
> cratering.
Ignoring the cones, which may be inaccurate if you bisqued them, it
definitely sounds overfired.
> >
> Is it possible that:
> >
> 1. I open the kiln too soon at 240 degrees? What temperature does
> everyone else open a glaze kiln?
This is not the source of your problem. I often open mine at 200 C,
which is around 400 F. If anything, this might cause crazing or
dunting, but not craters and bloats.
> 2. my ware is too close together? (nothing ever touches)
Nope, don't think so.
> 3. I use too much water when I throw?
Unrelated. All water is long gone by the time you've bisqued your
pieces.
> 4. I should not fire so many different clays or glazes in one load?
>
Possible, but unlikely. Some glazes do interact badly with one
another, but not usually in this way. More often the color response
changes, like with tin white glazes turning pink when chrome is
present in other glazes.
>
>
> Does anyone have any suggestions I might try? My glaze notes indicate
> that a cone 5 firing with a 30 min. hold at slow speed resulted in no
> craters, but the Opulence people told me their glazes should fire at a
> =93good cone 6=94 or even a =937=94.
>
Go with what works. If cone 5 was successful, stick with that. It's
possible that their glazes are capable of higher firing, but what you
have experienced is more likely an interaction of glaze and clay.
Perhaps their glazes work on some clays at cone 7, but perhaps
not on yours.
> > Why would my cones not bend all the way down? When I last checked th=
e
> temp on my kiln it was at 2165, although I got busy and forgot to check
> at the very end to see if it reached 2199. After 14.5 hours (including
> the 30 min. hold), it was at 2035.
See comments above, unless I misunderstood what you did with
your cones.
>
> I will really appreciate any help or suggestions.
>
Go with what works, and don't ever bisque fire your cones. It's no
good insisting that things should have been different because
someone told you that, theoretically, they would be. You have to
find, by trial and error, what works with your clay and your glazes,
in your kiln.
Good luck.
Chris Schafale
Light One Candle Pottery
Fuquay-Varina, North Carolina, USA
(south of Raleigh)
candle@intrex.net
http://www.lightonecandle.com
Snail Scott on sun 6 oct 02
At 01:09 AM 10/6/02 -0400, you wrote:
>Hi =96 I just opened my scutt kiln with automatic controller at 240
>degrees.=20
>NONE OF
>THE CONE 6=92s bent all the way down...
>Is it possible that:
>1. I open the kiln too soon at 240 degrees? What temperature does
>everyone else open a glaze kiln?=20
>2. my ware is too close together? (nothing ever touches)=20
>3. I use too much water when I throw?=20
>4. I should not fire so many different clays or glazes in one load?
Relax, it's none of the above. NONE of those things will
cause a kiln to underfire. Just keep doing what you've=20
been doing; you're not doing anything wrong. The load is=20
simply underfired.
It's your controller at fault - more than likely, the=20
thermocouple just needs a replacement. They don't last=20
forever. Just get a new one from a supplier, install it,=20
and refire the work. It should all come out just fine in=20
the next firing.=20
-Snail
Reno, NV
BobWicks@AOL.COM on sun 6 oct 02
I'm told you never open a kiln with automatic temperature control when it is
above 200 deg. F.
Bob
Dale Cochoy on sun 6 oct 02
----- Original Message -----
From: "Snail Scott"
Subject: Re: disappointing kiln opening
At 01:09 AM 10/6/02 -0400, you wrote:
>NONE OF
>THE CONE 6's bent all the way down...
>Is it possible that:
>1. I open the kiln too soon at 240 degrees? What temperature does
>everyone else open a glaze kiln?
>2. my ware is too close together? (nothing ever touches)
>3. I use too much water when I throw?
>4. I should not fire so many different clays or glazes in one load?
Relax, it's none of the above. NONE of those things will
cause a kiln to underfire. Just keep doing what you've
been doing; you're not doing anything wrong. The load is
simply underfired.
It's your controller at fault - more than likely, the
thermocouple just needs a replacement. They don't last
forever. Just get a new one from a supplier, install it,
and refire the work. It should all come out just fine in
the next firing.
-Snail
Reno, NV
A couple months ago I had similar problems but with another brand
Evenheat) kiln. In fact, I fired twice because I thoyught it might have
shut off early during a storm at the time since our power drops in/out a lot
during storms. But, that wasn't it.
I replaced thermocouple and fired again, same thing. It said it fired
complete and shut off but it was around cone 06ish I figured but didn't have
any conmes that low ion there. Glazes were not even started to melt.( I was
firing to cone 6). I called manufacturer and they told me to send in
controller PC board. I took it out and sent it and they replaced a chip. It
cost about $25 as I recall. ALSO, at the same time I ordered a
pyrometer/meter. Well, they fixed it and I have a pyrometer now to check
these things just in case my digital might be questionable. I will add that
my digital has been perfect every time up to, and after the problem.
Electronics fail some times. And, I always have an extra thermocouple on
hand now.
Regards,
Dale Cochoy.
Arnold Howard on mon 7 oct 02
Snail offered good advice about replacing the thermocouple when a
digital controller shuts off prematurely.
If the temperature is way off, you probably need a new
thermocouple. They are fairly easy to replace. I would keep a spare
on hand.
If the temperature is only slightly off, you can re-calibrate the
controller. (Unless your model is dated before around 1986.)
Thermocouples all read temperature a little differently. You can
re-calibrate the controller to compensate for the thermocouple.
(Your instruction manual will cover re-calibration if your
controller has that feature.)
If your controller cannot be re-calibrated, you can compensate by
adding a temperature hold.
It's very good that you are using witness cones with your digital
controller. Otherwise you would not know for sure what went wrong.
One time I surveyed 60 elementary and high school school teachers
who fired kilns. Only two of them used witness cones.
With best wishes,
Arnold Howard
Paragon Industries, Inc.
--- Snail Scott wrote:
> At 01:09 AM 10/6/02 -0400, you wrote:
> >Hi – I just opened my scutt kiln with automatic controller at
> 240
> >degrees.
> >NONE OF
> >THE CONE 6’s bent all the way down...
> >Is it possible that:
> >1. I open the kiln too soon at 240 degrees? What
> temperature does
> >everyone else open a glaze kiln?
> >2. my ware is too close together? (nothing ever touches)
> >3. I use too much water when I throw?
> >4. I should not fire so many different clays or glazes in
> one load?
>
>
>
> Relax, it's none of the above. NONE of those things will
> cause a kiln to underfire. Just keep doing what you've
> been doing; you're not doing anything wrong. The load is
> simply underfired.
>
> It's your controller at fault - more than likely, the
> thermocouple just needs a replacement. They don't last
> forever. Just get a new one from a supplier, install it,
> and refire the work. It should all come out just fine in
> the next firing.
>
> -Snail
> Reno, NV
>
__________________________________________________
Do you Yahoo!?
Faith Hill - Exclusive Performances, Videos & More
http://faith.yahoo.com
Mark Moesch on mon 7 oct 02
I had a very disappointing first firing in my Skutt also. The cone 6 =
slow schedule took a long time and ended up overfiring. Most of my =
pieces stuck to my shelves. I have started using the Ron and John =
firing schedule that can be found on the http://www.masteringglazes.com =
This cleaned everything up just fine and cone 6 just touches. =20
If this doesn't work, I would check the pyrometer as mentioned in =
previous posts.
Cliff/Karen Sandlin on tue 8 oct 02
Ron: thanks for responding. The craters were on the highwater
redstone, laguna #60, and highwater desert buff clays. I think on
Laguna's B-Mix for cone 6 also. The craters were with Spectrum textured
glazes and with Opulence (though not as pronounced). =20
The man at Skutt instructed me on how to offset the temperature for Cone
6 (on my automatic controller) for 10 degrees hotter. When I refired at
Cone 5, slow speed, 30 min. hold, the self-supporting cones on top and
bottom shelves bent only very slightly. =20
I plan to call Skutt again today (3 hr. time difference) and see if it
could possibly help to refire the entire load (after I dremel the
craters), using the SLOW COOLING ramp and hold segment program in my
Skutt user's manual.
I have a show coming up and can't afford to lose this entire load, so I
have my fingers crossed. =20
I've not had the problem using the same clays with Cone 5 Moroccan Sand
glazes. I've also used the same clays with other Opulence glazes with
no craters.
Karen
Karen
-----Original Message-----
From: Ron Roy [mailto:ronroy@total.net]=20
Sent: Tuesday, October 08, 2002 1:25 AM
To: sandlink@bellsouth.net
Subject: Re: disappointing kiln opening
Hi Karen,
The "bumps" make me think it may be a bad batch of clay - was it froma
new
batch - when clay is over vitrified it begines to form bubbles in the
body
- the bumps and glazes will be overfired from the clay melting - best to
call your supplier and ask if there have been any other reports like
yours.
Mistakes do happen.
If it happened to the same clays then for sure - but if it happend to
all
then I don't nkow what happened. You should have told us what happend to
what clay.
RR
>Hi =96 I just opened my scutt kiln with automatic controller at 240
>degrees. My kiln has only been fired 31 times (04 bisque, cone 5 and
>cone 6) and is 2 yrs. old. I bisqued this load to Cone 03 at SLOW
>speed. I glazed by brushing on mostly layered Opulence and some
>Spectrum glazes (that I have used before) on Highwater Redstone, Desert
>Buff, and Laguna 50 and B-Mix clays. I set the controller to Cone 6,
>SLOW speed, with a 30 min. hold.
>
>
>
>I had bisqued bits of clay holding large cone 6=92s and placed them =
about
>on various shelves. My ware was about =BD=94 apart.
>
>
>
>According to the skutt manual, I propped the lid till 1000 degrees,
then
>closed the lid and always keep the top peephole unplugged.
>
>
>
>Some of my pieces have craters. Some have bumps. Some of the Opulence
>glazes that have been matt finishes in the past are very shiny. NONE
OF
>THE CONE 6=92s bent all the way down. The cones on the top and bottom
>shelves are totally upright; on the middle two shelves, they are bent
>very slightly. I do the slow speed and the 30 min. hold to minimize
>cratering.
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513=20
Cliff/Karen Sandlin on tue 8 oct 02
Ron: thanks for responding. The craters were on the highwater
redstone, laguna #60, and highwater desert buff clays. I think on
Laguna's B-Mix for cone 6 also. The craters were with Spectrum textured
glazes and with Opulence (though not as pronounced).
The man at Skutt instructed me on how to offset the temperature for Cone
6 (on my automatic controller) for 10 degrees hotter. When I refired at
Cone 5, slow speed, 30 min. hold, the self-supporting cones on top and
bottom shelves bent only very slightly.
I plan to call Skutt again today (3 hr. time difference) and see if it
could possibly help to refire the entire load (after I dremel the
craters), using the SLOW COOLING ramp and hold segment program in my
Skutt user's manual.
I have a show coming up and can't afford to lose this entire load, so I
have my fingers crossed.
I've not had the problem using the same clays with Cone 5 Moroccan Sand
glazes. I've also used the same clays with other Opulence glazes with
no craters.
Karen
-----Original Message-----
From: Ron Roy [mailto:ronroy@total.net]
Sent: Tuesday, October 08, 2002 1:25 AM
To: sandlink@bellsouth.net
Subject: Re: disappointing kiln opening
Hi Karen,
The "bumps" make me think it may be a bad batch of clay - was it froma
new
batch - when clay is over vitrified it begines to form bubbles in the
body
- the bumps and glazes will be overfired from the clay melting - best to
call your supplier and ask if there have been any other reports like
yours.
Mistakes do happen.
If it happened to the same clays then for sure - but if it happend to
all
then I don't nkow what happened. You should have told us what happend to
what clay.
RR
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
| |
|
