mel jacobson on thu 29 dec 05
i fire over night all the time.
but:
i never let the kiln get over 500F.
so, i leave two switches on low.
in this way all the smoke and goober is
out of the kiln when i turn the kiln to
medium early in the morning. the vent
has removed the most critical crap while
i sleep.
many things in my home are cycling electrically over
night. water heater, furnace, and many more. they are
safe because we make sure they are. i make sure the
kiln wiring is checked, has a good breaker, wires are the
right size. kiln is in a back room, with venting.
never auto fire to max temp over night...never.
it is only preheat.
of course i get up early...maybe 5 a.m. to get
things going.
i do not think i am wasting amps. it takes X time
to get to X temp. if you go slow you are using very
little amperage to get there.
also, if you are going to fire that bisque kiln at night
to reach final temp...you are tempted to go to sleep with it
still firing. that never happens with a kiln you start at 500f at 5 a.m.
it is done by 1 p.m. alarm clock set to check it.
a kiln on high is taking max amperage. so, i go slow
in the beginning. i am convinced that many
problems we encounter with glaze flaws are the result of
fast bisque firing. (ron roy infomation)
my major concern is lost work, bloating, pinholes.
wasting firing time to achieve seconds to me is the
biggest waste in ceramics. firing for 100 percent
quality is the best firing technique for the ecologist.
mel
safe and efficient firing schedules are the best system
a potter can have. fire at the same time, same schedule
every time. never vary. it is the odd firing, at an odd time
that you forget. those are always the kilns that stick, or the
cone does not go down. murphy's law. 100 ruined pots.
from mel/minnetonka.mn.usa
website: http://my.pclink.com/~melpots3
Bruce Lucas on thu 29 dec 05
mel jacobson wrote:
> i do not think i am wasting amps. it takes X time
> to get to X temp. if you go slow you are using very
> little amperage to get there.
This is probably largely true, at the low temperature you are talking
about. It would be exactly true, and true at any temperature, if the
kiln were perfectly insulated.
Every bit of energy that you put into the kiln goes into one of two
things: 1) increasing the temperature of the kiln and the ware, or 2)
replacing heat that escapes from the kiln.
A fixed amount of energy (measured in kilowatt hours) is required to
increase the temperature of the kiln and the ware by a certain amount,
regardless of whether its slow (say 1 kilowatt for 5 hours) or fast (say
5 kilowatts for 1 hour).
But the amount of energy required to replace the heat that escapes from
the kiln depends on the temperature difference between the kiln and its
environment. At low temperatures very little heat is escaping so very
little energy is required to replace the escaping heat. At high
temperatures a lot of heat is escaping, requiring a lot of energy to
replace it. So a slow firing at high temperature does require more
energy. This energy may not be wasted of course if it is going to
heating your studio.
The maximum temperature that the kiln is capable of reaching is the
temperature at which heat is escaping as fast as it can be replaced,
given the kilowatt rating of the kiln. I like to think of it as if you
were trying to fill a leaky bucket. The water escapes from the bucket
at a rate that depends on the amount of water in the bucket. When the
bucket is nearly empty very little is escaping and most of the water
from the tap goes into increasing the water level. As it gets fuller
the water escapes faster until it reaches a level where water is
escaping as fast as your tap can fill it, and the water level increases
no further.
Bruce Lucas
William & Susan Schran User on thu 29 dec 05
On 12/29/05 9:46 AM, "mel jacobson" wrote:
> many things in my home are cycling electrically over
> night. water heater, furnace, and many more. they are
> safe because we make sure they are
The many things we have in our home - furnace, water heater, etc. - that ar=
e
made to automatically cycle on & off and have been tested to perform in thi=
s
manner. In the U.S. most equipment is tested by Underwriters Laboratories,
and gets their seal if they perform as intended.
Though most electric kilns are UL listed, they are periodic devices, not
intended to be unattended while in use. Most manufacturers write in their
instructions: "Never leave the kiln unattended while firing."
Each person has their point at what they see as reasonable/comfortable.
Mel fires his bisque on low overnight to reach 500=B0F when he turns it up in
the morning. To him this is reasonable and he is comfortable with this
process.
For me, I check the progress of all my firings a minimum of once an hour.
For me this is reasonable and I am comfortable.
I think Mel would agree, programming a kiln to complete a firing, turning i=
t
on, then leaving or going to bed, may not be the most prudent way to fire a
kiln.
-- William "Bill" Schran
Fredericksburg, Virginia
wschran@cox.net
wschran@nvcc.edu
Hank Murrow on thu 29 dec 05
On Dec 29, 2005, at 8:21 AM, Bruce Lucas wrote:
>
> Every bit of energy that you put into the kiln goes into one of two
> things: 1) increasing the temperature of the kiln and the ware,
And if the refractories the kiln is made of store less heat, you are
heating mainly the wares and furniture. Fiber insulations are very
useful here, as is lightweight furniture.
> or replacing heat that escapes from the kiln.
The biggest portion of which goes to heat the Nitrogen (89%) that is in
the air in the case of a fuel-burning kiln.
> But the amount of energy required to replace the heat that escapes from
> the kiln depends on the temperature difference between the kiln and its
> environment. At low temperatures very little heat is escaping so very
> little energy is required to replace the escaping heat. At high
> temperatures a lot of heat is escaping, requiring a lot of energy to
> replace it. So a slow firing at high temperature does require more
> energy.
My Doorless Fiberkiln fires a long cycle of 30 hours or so (because I
like how the glazes turn out) and also a soak for 4 to 8 hours during
cooling, for a cost of $24 per firing in natural gas. The reason it
fires so long for few $$ is that it stores very little heat in its
fiber lining, is sealed except for the ports and the flue, and also
because of the reflective nature of ceramic fiber after red heat.
>
> The maximum temperature that the kiln is capable of reaching is the
> temperature at which heat is escaping as fast as it can be replaced,
> given the kilowatt rating of the kiln. I like to think of it as if you
> were trying to fill a leaky bucket. The water escapes from the bucket
> at a rate that depends on the amount of water in the bucket. When the
> bucket is nearly empty very little is escaping and most of the water
> from the tap goes into increasing the water level. As it gets fuller
> the water escapes faster until it reaches a level where water is
> escaping as fast as your tap can fill it, and the water level increases
> no further.
Nice metaphor, Bruce!
Cheers, Hank
www.murrow.biz/hank
Elizabeth Priddy on thu 29 dec 05
I have the kiln setter with the cone. And also
the timer that turns the kiln off regardless after a certain
number of hours. The digital I only fire when I am going
to be awake and home. I actually prefer the kiln
with the knobs to the digital. But then I like simple
firing and soaks are just as easy with knobs.
the reason to fire to hit temperature at the crack of
dawn here at the coast is the issue of AC v kiln as
draw at peak times. The diabetes and the general
intolerance of heat make AC a necessary element of
life here. Otherwise, I would have to move to places
that just don't get that hot or that humid.
Back before it was ubiquitous, a lot of people with
health issues moved to Arizona and CA.
When the power goes out due to storms, I leave.
Not cause of the hurricane, but the dense humidity
with no power to make it go away.
The house is sufficiently wired to do both, but the
local power grid can go down due to the AC draw
when the temp and humidity get to cycling. And I
don't want the firing to go awry due to this. It did
happen once and that was sufficient to just do it overnight.
E
Elizabeth Priddy
Beaufort, NC - USA
http://www.elizabethpriddy.com
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Alyssa Ettinger on sat 31 dec 05
just came into this thread so don't know what precipitated it.
in my now former studio--former as of 2 weeks ago--we always fired the
electric kilns (with the electronic controls) overnight because we a: didn't
want to heat up the studio during the day, and b: didn't want to be
breathing those fumes. but, the former studio was all cement.
our new studio is not cement but wood; two of the walls are brick, the other
two dry-wall. the floor is wood as well, and we're planning on putting the
kiln on either cement blocks, a layer of bricks, or a sheet of steel. it
never occurred to me until reading this post that we possibly shouldn't be
firing while we weren't there. (i should have thought of this--sorry jane,
you really did teach me well...--but it didn't cross my mind till now.)
am i correct in assuming that firing while we're not there is a very bad idea?
Arnold Howard on mon 2 jan 06
Bill is correct. The warning label on the kiln is an important part of the
UL Listing. One of the things a UL inspector looks for when he visits a kiln
factory is the warnings silk-screened onto the kiln. If it has been reworded
in any way, the inspector will make the manufacturer re-silkscreen all the
switch boxes.
Sincerely,
Arnold Howard
Paragon Industries, L.P., Mesquite, Texas USA
ahoward@paragonweb.com / www.paragonweb.com
----- Original Message -----
From: "William & Susan Schran User"
The many things we have in our home - furnace, water heater, etc. - that are
made to automatically cycle on & off and have been tested to perform in this
manner. In the U.S. most equipment is tested by Underwriters Laboratories,
and gets their seal if they perform as intended.
Though most electric kilns are UL listed, they are periodic devices, not
intended to be unattended while in use. Most manufacturers write in their
instructions: "Never leave the kiln unattended while firing."
Earl Brunner on wed 4 jan 06
It's a liability issue for them. Imagine if they SAID it was OK, then your studio burned down for some one in a million malfunction.......
These are fun: http://www.mlaw.org/wwl/index.html
Earl Brunner e-mail: brunv53@yahoo.com
----- Original Message ----
From: William & Susan Schran User
To: CLAYART@LSV.CERAMICS.ORG
Sent: Wednesday, January 04, 2006 5:32:56 PM
Subject: Re: firing over night
On 12/31/05 11:15 AM, "Alyssa Ettinger" wrote:
> am i correct in assuming that firing while we're not there is a very bad idea?
Well, I think all kiln manufacturers write in their instructions: "never
leave kiln unattended while firing.", so I guess they think it's a bad idea.
-- William "Bill" Schran
Fredericksburg, Virginia
William & Susan Schran User on wed 4 jan 06
On 12/31/05 11:15 AM, "Alyssa Ettinger" wrote:
> am i correct in assuming that firing while we're not there is a very bad idea?
Well, I think all kiln manufacturers write in their instructions: "never
leave kiln unattended while firing.", so I guess they think it's a bad idea.
-- William "Bill" Schran
Fredericksburg, Virginia
wschran@cox.net
wschran@nvcc.edu
Arnold Howard on thu 5 jan 06
From: "William & Susan Schran User"
>> am i correct in assuming that firing while we're not there is a very bad
>> idea?
>
> Well, I think all kiln manufacturers write in their instructions: "never
> leave kiln unattended while firing.", so I guess they think it's a bad
> idea.
Two weeks ago a friend left his 3-zone kiln firing in his studio while he
went home. When he returned, the controller showed FTL and the kiln was off,
but it was still glowing inside. Ordinarily it would have been much cooler
by the time he reached his studio.
After it cooled, he opened it to find that the bricks had crystallized and
the ware and shelves had collapsed into the bottom. (The elements, however,
were still good!) "I've fired kilns 12,000 times, and this is my first
overfiring," he said.
The digital kiln (and the Kiln Sitter) are very reliable. Overfires are
rare. But when they do happen, the kiln manufacturer hears about it. That is
why we unanimously recommend that you are with the kiln while it fires.
Some kilns cannot overfire, though. There are 120-volt china painting kilns
that cannot get hotter than around 1700F. You can fire them all night if you
want. Or if you turn one switch on Low, as Mel does, the kiln cannot
overfire. But ordinarily you should attend to the kiln while it is firing.
One time I was firing the Paragon QuikFire (an extremely fast ceramic fiber
kiln). I answered the phone, and when I returned to the kiln, it had
overfired and destroyed the element.
Sincerely,
Arnold Howard
Paragon Industries, L.P., Mesquite, Texas USA
ahoward@paragonweb.com / www.paragonweb.com
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