Paula Mann on thu 25 nov 04
In September I bought a used Skutt 183-27 from a neighbor, had new =
elements installed and switches checked, all systems go.
I've been trying to extend my firing times since my glaze firings reach =
cone and the kiln sitter shuts down at about 8 hours (I usually fire to =
cone 5 with a cone 6 rod in the sitter). In early firings I didn't =
worry too much about time and all shelves were at cone after about 8 =
hours but after reading and listening to other potters I figured 8 hours =
was way too short a time for firing.
If I move the temperatures up more slowly the sitter still shuts down =
after 8 hours but the witness cones on the shelves indicate they're not =
reaching cone.
I sure could use some help. Should I be happy with my 8 hour firing, =
even though I hear other potters pshaw at such a short time? Or can you =
firing gurus give me some tips to work the timing better? If a =
pyrometer is the answer I still would appreciate some help with the =
timing as I ramp up the heat.
New potter in distress,
Paula in Ft. Collins, CO
william schran on fri 26 nov 04
Paula wrote:>If I move the temperatures up more slowly the sitter
still shuts down after 8 hours but the witness cones on the shelves
indicate they're not reaching cone.
I sure could use some help. Should I be happy with my 8 hour firing,
even though I hear other potters pshaw at such a short time? Or can
you firing gurus give me some tips to work the timing better? If a
pyrometer is the answer I still would appreciate some help with the
timing as I ramp up the heat.<
I would not be too concerned about an 8 hour firing cycle. I would
recommend you fire by the witness cones and only use the sitter as an
emergency back-up - so that means putting a higher cone in the sitter.
What you do want is a slow cool and a short hold at top temp - so
that means a pyrometer. Once you reach your desired firing cone, then
adjust the controls for a 1/2 hour hold, then a slow drop in
temperature, again through control adjustment.
Bill
Mark Tigges on fri 26 nov 04
On Thu, Nov 25, 2004 at 09:21:51PM -0700, Paula Mann wrote:
> I've been trying to extend my firing times since my glaze firings
> reach cone and the kiln sitter shuts down at about 8 hours (I
> usually fire to cone 5 with a cone 6 rod in the sitter). In early
> firings I didn't worry too much about time and all shelves were at
> cone after about 8 hours but after reading and listening to other
> potters I figured 8 hours was way too short a time for firing. If I
> move the temperatures up more slowly the sitter still shuts down
> after 8 hours but the witness cones on the shelves indicate they're
> not reaching cone. I sure could use some help. Should I be happy
> with my 8 hour firing, even though I hear other potters pshaw at
> such a short time? Or can you firing gurus give me some tips to
> work the timing better? If a pyrometer is the answer I still would
> appreciate some help with the timing as I ramp up the heat.
Hi Paula,
You need to put in a higher cone in the kiln sitter. As simple as
that. I fire to cone 6 and I use a cone 9. The small cone sitter
cones are very inaccurate. Yesterday my kiln sitter tripped during
the cooling phase, I was about half way through my cooling cycle and
the cone 9 cone had melted enough. Very strange, first time that's
happened. Well, when I looked in this morning, the kiln sitter cone
had actually fractured on the bottom part, enabling it to bend
easier.
By the way, as far as I understand, (I'm closer to your level of
experience than I am the experts that join in on clayart), it's not
just the length of time that is important. The rate of heating and
cooling at various points of the firing that is the most important
(and my results bear that out). In particular slow cooling from your
peak down to 800C. I peak my cone 6 firings at about 1185C with a
long soak there, and then cool slowly down to 800C.
Getting a pyrometer was the best thing I did. I just drilled a hole
through a soft brick peep-hole plug and stuck it through that. Having
the information of temperature even if the absolute temperature is
only relatively accurate is a huge help. Without it it's much more
difficult to maintain a good heating/cooling rate. It's helped me
fire my kiln much more efficiently. I wrote myself a little computer
program to plot the curve of temperature and time during the firing
and it's gotten to the point where I know what the pots will be like
by looking at the curve. Get a pyrometer.
Best regards,
Mark.
BTW, a good book for cone 6 glazes "Mastering Cone 6 Glazes"
recommends a firing cycle that reaches 1200C in only 6 hours. But the
firing continues through holding and slow cooling all the way to 11
plus hours. The ramp up though uses three different rates,
importantly slow for the last 100C. If you don't have the book I can
highly recommend it. The authors are even very helpful here on
clayart.
Cindy on fri 26 nov 04
Hello, Paula
First--read your kiln manual. I used to have a kiln with a kiln sitter, and
there was a way to calibrate the kiln to make it fire more closely to the
shelf cones. It was a simple adjustment, but I don't remember just what
needed to be done. I expect it varies with different kiln sitters. If you
don't have a manual, do an on-line search. If you can't find an on-line
manual, write to or phone the manufacturer.
Second, if the adjustment is inadequate to solve your kiln's inaccuracy, use
a higher cone. Examine your cones before using them--you don't want a
cracked or otherwise irregular one. Also, make sure the prongs are free of
any glaze or other deposits. This usually makes the kiln fire too hot, which
isn't your problem, but it's a good idea to check in any case.
Third, do use shelf cones. I like the self-standing ones. Place them a
little ways away from the peepholes (to avoid drafts)and make sure you have
a clear view through the kiln with nothing behind the cone or behind the
space where the cone will bend to. Cones are hard enough to see without
obstructions. This limits your shelf space, but not as much as you might
expect. The cones are much less useful if you can't see them during the
firing. Use dark safety glasses to protect your eyes.
If the kiln sitter has dropped and your cones haven't bent to a little less
than half, you can prop the sitter back up until the cones are bent to
between 1/4 and 1/3 of the way down. They will bend the rest of the way
before the kiln cools. It's kind of like turning off your electric stove
before the eggs are quite done. If you do this, take a folding chair and
plop it down right by your kiln and sit there until the kiln is finished and
you have unpropped the kiln sitter.
Firing down a kiln with a kiln sitter is time consuming and maybe so--maybe
not worth the effort. It will affect some glazes, but not all. If you're
using shiny glazes, don't bother. If you're trying to get crystalline
mattes, then you may need to fire down. A pyrometer is helpful for this. You
will need to attend the kiln constantly.
Turn off two or more elements, keeping the kiln sitter propped up. You will
need to determine how many elements to switch off by experimentation. A
pyrometer will help with this, but you can also tell a bit by the color of
the heat (hard to do if you haven't the experience). If memory serves, you
want to slow the cooling at around 1800 F. and hold it there for about an
hour. After this, you should unprop the kiln sitter and allow the kiln to
cool naturally, lid closed. Remember--you must attend the kiln at all times
when the sitter is propped.
Oh and by the way, never trust the kiln sitter or any other mechanical or
digital device to turn off your kiln for you. They usually work, but they
absolutely do not work all of the time.
Best wishes,
Cindy in SD
Anne Wellings on fri 26 nov 04
A higher cone in the sitter is a good idea. But maybe not everyone realizes
that if your kiln sitter shuts off before you want it to (before the
witness cones on the shelf have melted to your satisfaction), you can turn
the kiln back on by lifting the lever, pushing the switch button, and then
lowering the lever slowly. Then, of course, you have to keep a close eye on
it, as the kiln will not shut off until you turn it off! Some say you
should turn the switches to LOW or OFF first (if you have manual switches),
and then to whatever you want them at, as having them on HIGH when you do
this is hard on the switch block. (What to do with a computerized kiln
having a kiln sitter, I do not know.) This has been discussed on the list
before, but bears repeating for those who do not know about it. I did not
know this until I had been making pottery for about 20 years!
Other than that, I do an 8 hour firing to about ^5.5, and it works for me.
I have manual switches and don't make a point of slow cooling, although I
try for a bit of a soak at the end if the cones are melting fast, by
turning things down to MED when the cones have dropped to about 10:00. This
works for the glazes I'm using, which are pretty much glossy. I think
whatever works for you with the pots you make and the glazes you use is OK!
If you are making really dense, thick pots, pack your kiln tightly, and are
using matte glazes and/or want lots of crystals, you should go for a slower
firing. Yes, the book Mastering ^6 Glazes is excellent, I have it and have
developed a wonderful yellow/gold glaze using one of its base recipes. It
goes into firing schedules and the reasons for slow cooling in depth.
Anne Wellings
Sunrise Beach Pottery
Olympia, Washington
On Fri, 26 Nov 2004 08:51:04 -0800, Mark Tigges wrote:
>On Thu, Nov 25, 2004 at 09:21:51PM -0700, Paula Mann wrote:
>> I've been trying to extend my firing times since my glaze firings
>> reach cone and the kiln sitter shuts down at about 8 hours (I
>> usually fire to cone 5 with a cone 6 rod in the sitter). In early
>> firings I didn't worry too much about time and all shelves were at
>> cone after about 8 hours but after reading and listening to other
>> potters I figured 8 hours was way too short a time for firing. If I
>> move the temperatures up more slowly the sitter still shuts down
>> after 8 hours but the witness cones on the shelves indicate they're
>> not reaching cone. I sure could use some help. Should I be happy
>> with my 8 hour firing, even though I hear other potters pshaw at
>> such a short time? Or can you firing gurus give me some tips to
>> work the timing better? If a pyrometer is the answer I still would
>> appreciate some help with the timing as I ramp up the heat.
>
>Hi Paula,
>
>You need to put in a higher cone in the kiln sitter. As simple as
>that. I fire to cone 6 and I use a cone 9. The small cone sitter
>cones are very inaccurate. Yesterday my kiln sitter tripped during
>the cooling phase, I was about half way through my cooling cycle and
>the cone 9 cone had melted enough. Very strange, first time that's
>happened. Well, when I looked in this morning, the kiln sitter cone
>had actually fractured on the bottom part, enabling it to bend
>easier.
>
>By the way, as far as I understand, (I'm closer to your level of
>experience than I am the experts that join in on clayart), it's not
>just the length of time that is important. The rate of heating and
>cooling at various points of the firing that is the most important
>(and my results bear that out). In particular slow cooling from your
>peak down to 800C. I peak my cone 6 firings at about 1185C with a
>long soak there, and then cool slowly down to 800C.
>
>Getting a pyrometer was the best thing I did. I just drilled a hole
>through a soft brick peep-hole plug and stuck it through that. Having
>the information of temperature even if the absolute temperature is
>only relatively accurate is a huge help. Without it it's much more
>difficult to maintain a good heating/cooling rate. It's helped me
>fire my kiln much more efficiently. I wrote myself a little computer
>program to plot the curve of temperature and time during the firing
>and it's gotten to the point where I know what the pots will be like
>by looking at the curve. Get a pyrometer.
>
>Best regards,
>
>Mark.
>
>BTW, a good book for cone 6 glazes "Mastering Cone 6 Glazes"
>recommends a firing cycle that reaches 1200C in only 6 hours. But the
>firing continues through holding and slow cooling all the way to 11
>plus hours. The ramp up though uses three different rates,
>importantly slow for the last 100C. If you don't have the book I can
>highly recommend it. The authors are even very helpful here on
>clayart.
>
Mark Tigges on sat 27 nov 04
Anne,
Would you mind sharing the yellow/gold recipe?
Mark.
On Fri, Nov 26, 2004 at 09:10:18PM -0500, Anne Wellings wrote:
> A higher cone in the sitter is a good idea. But maybe not everyone realizes
> that if your kiln sitter shuts off before you want it to (before the
> witness cones on the shelf have melted to your satisfaction), you can turn
> the kiln back on by lifting the lever, pushing the switch button, and then
> lowering the lever slowly. Then, of course, you have to keep a close eye on
> it, as the kiln will not shut off until you turn it off! Some say you
> should turn the switches to LOW or OFF first (if you have manual switches),
> and then to whatever you want them at, as having them on HIGH when you do
> this is hard on the switch block. (What to do with a computerized kiln
> having a kiln sitter, I do not know.) This has been discussed on the list
> before, but bears repeating for those who do not know about it. I did not
> know this until I had been making pottery for about 20 years!
>
> Other than that, I do an 8 hour firing to about ^5.5, and it works for me.
> I have manual switches and don't make a point of slow cooling, although I
> try for a bit of a soak at the end if the cones are melting fast, by
> turning things down to MED when the cones have dropped to about 10:00. This
> works for the glazes I'm using, which are pretty much glossy. I think
> whatever works for you with the pots you make and the glazes you use is OK!
> If you are making really dense, thick pots, pack your kiln tightly, and are
> using matte glazes and/or want lots of crystals, you should go for a slower
> firing. Yes, the book Mastering ^6 Glazes is excellent, I have it and have
> developed a wonderful yellow/gold glaze using one of its base recipes. It
> goes into firing schedules and the reasons for slow cooling in depth.
>
> Anne Wellings
> Sunrise Beach Pottery
> Olympia, Washington
>
>
> On Fri, 26 Nov 2004 08:51:04 -0800, Mark Tigges wrote:
>
> >On Thu, Nov 25, 2004 at 09:21:51PM -0700, Paula Mann wrote:
> >> I've been trying to extend my firing times since my glaze firings
> >> reach cone and the kiln sitter shuts down at about 8 hours (I
> >> usually fire to cone 5 with a cone 6 rod in the sitter). In early
> >> firings I didn't worry too much about time and all shelves were at
> >> cone after about 8 hours but after reading and listening to other
> >> potters I figured 8 hours was way too short a time for firing. If I
> >> move the temperatures up more slowly the sitter still shuts down
> >> after 8 hours but the witness cones on the shelves indicate they're
> >> not reaching cone. I sure could use some help. Should I be happy
> >> with my 8 hour firing, even though I hear other potters pshaw at
> >> such a short time? Or can you firing gurus give me some tips to
> >> work the timing better? If a pyrometer is the answer I still would
> >> appreciate some help with the timing as I ramp up the heat.
> >
> >Hi Paula,
> >
> >You need to put in a higher cone in the kiln sitter. As simple as
> >that. I fire to cone 6 and I use a cone 9. The small cone sitter
> >cones are very inaccurate. Yesterday my kiln sitter tripped during
> >the cooling phase, I was about half way through my cooling cycle and
> >the cone 9 cone had melted enough. Very strange, first time that's
> >happened. Well, when I looked in this morning, the kiln sitter cone
> >had actually fractured on the bottom part, enabling it to bend
> >easier.
> >
> >By the way, as far as I understand, (I'm closer to your level of
> >experience than I am the experts that join in on clayart), it's not
> >just the length of time that is important. The rate of heating and
> >cooling at various points of the firing that is the most important
> >(and my results bear that out). In particular slow cooling from your
> >peak down to 800C. I peak my cone 6 firings at about 1185C with a
> >long soak there, and then cool slowly down to 800C.
> >
> >Getting a pyrometer was the best thing I did. I just drilled a hole
> >through a soft brick peep-hole plug and stuck it through that. Having
> >the information of temperature even if the absolute temperature is
> >only relatively accurate is a huge help. Without it it's much more
> >difficult to maintain a good heating/cooling rate. It's helped me
> >fire my kiln much more efficiently. I wrote myself a little computer
> >program to plot the curve of temperature and time during the firing
> >and it's gotten to the point where I know what the pots will be like
> >by looking at the curve. Get a pyrometer.
> >
> >Best regards,
> >
> >Mark.
> >
> >BTW, a good book for cone 6 glazes "Mastering Cone 6 Glazes"
> >recommends a firing cycle that reaches 1200C in only 6 hours. But the
> >firing continues through holding and slow cooling all the way to 11
> >plus hours. The ramp up though uses three different rates,
> >importantly slow for the last 100C. If you don't have the book I can
> >highly recommend it. The authors are even very helpful here on
> >clayart.
> >
>
> ______________________________________________________________________________
> 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.
Arnold Howard on mon 29 nov 04
You can download the Dawson Kiln Sitter manuals at this link:
http://tinyurl.com/5449x
Sincerely,
Arnold Howard
Paragon Industries, L.P., Mesquite, Texas USA
arnoldhoward@att.net / www.paragonweb.com
From: "Cindy"
> First--read your kiln manual. I used to have a kiln with a kiln sitter,
> and
> there was a way to calibrate the kiln to make it fire more closely to the
> shelf cones. It was a simple adjustment, but I don't remember just what
> needed to be done. I expect it varies with different kiln sitters. If you
> don't have a manual, do an on-line search. If you can't find an on-line
> manual, write to or phone the manufacturer.
| |
|
