mel jacobson on thu 15 mar 12
i was up early (four a.m.) firing my kiln.
i have posted this before, but as long as we
have pdf's flying across the world with kiln plans,
it is good to insert some ideas about the `process of firing`,
not kiln architecture.
for years the wisdom was always about slow early firing.
in fact many will fire for hours with one burner on half power.
the kiln just fired slow and slower. `gotta go slow you know`..why?
or, even all night candle with one burner.
it is mostly total bs.
if you have well fired bisque, and your glazes are dry, fire your
kiln with full power right off the bat. why the slow?
you want to build energy in your kiln, as fast as you can.
get the energy into the kiln...and that would be heat.
as you fire the kiln heat moves through the brick and leaks
out into the room. that is natural.
but, as the heat leaves the kiln, so does the insulating property
of the brick. the longer your early firing, the more you lose
insulation. that is the K factor of your brick.
so: what does a long early, slow firing do for you? costs you
fuel, money, time and the kiln and pots do not care.
and, at a time when fuel costs and ecology is front and center,
why waste it on theory that is 90 years old?
fire for speed and proper balance. and balance and rhythm are
front and center.
you feel the firing, you sense things with experience, you
can hear the kiln, smell the kiln, feel the kiln.
for example. if your kiln is spewing flame from the stack,
you have an 18 inch flame from the peep hole when you
check the cones....you have an outrageous firing going on.
most of your fuel is warming the atmosphere. nothing is
staying in the kiln.....and what you are heating, should be inside
the kiln. not the outside.
i fire my kiln with a 40 foot gas line from my house to my garage.
one and half inch black pipe, buried. it has been underground
for almost 50 years. it attaches to my house meter.
all the conventional wisdom says: `that will not work, not near
enough gas pressure, it will not work`...well, it does, and has
for thousands of firings.
many kilns fire with far too much pressure, not too little.
(i can't tell you how much time and energy i have spent
traveling fixing kilns, helping folks.) in most cases the
kiln is fine...they just `over fire`. hit the gas pedal to
the floor and heat the outside world. i fire the kiln with
half the gas, in half the time, with much better glazes
from the kiln. of course, the glazes are brighter, not
so heavily reduced, and, often the potter does not see the
`better quality`...they are used to over fired, over reduced pots.
i have no issues with professional potters that have a system in
place for their work. that is their business, and if it works for them..
fine. they know what they are doing...and have a background
to rely on. if your glazes need time, so be it. that is up to the
potter in charge.
i just hate waste and ignorance of basic thermo/dynamics and
the in your face....`we have always done it this way`.
and that is the problem, never change, live in 1930, but
they will hit you in the face if you throw a soda can away.
but, they just wasted fuel by the ton, and heated the world
at large...they just did not understand it. ecologist with
no brain in place...just platitudes. and then they tell you
that industry wastes gas and electricity...are you kidding??.
when your gas bill is two million dollars a year, do you
think they waste it...???? engineers plot every btu, every
ounce, every amp. companies go to great lengths to
conserve every ounce of energy. if not, profit goes out
the window.
almost everything we use and buy is heat treated. metal, plastic,
wood, even paper. the product is tempered with heat. it has
to be controlled to perfection. no waste.
if more potters looked at industry and sought information
about gas, fire, heat and energy, we would have better pots.
and, we would not waste very much.
this is how i fire...every time:
i leave a tiny burner on over night...it is like a big pilot.
it warms the kiln, pots and furniture/advancers to about
400F. like your home oven. the wax melts and the stack
warms. heat is building, but the brick is cold.
i open my flue/damper and heat it with a burnzomatic torch and watch
the heat go up...as in up the chimney. now the gas/heat
is going in the right direction.
i turn on both of my burners to `full`.
i hit it.
when the kiln reaches 1700f i turn the kiln down 1/3rd.
i slide in the damper so that about two inches of soft flame
comes from my main peep, halfway up the kiln front.
as the kiln reaches 2100f, i turn the burners down to half.
at 2200f i turn it down to only a fourth of the gas is flowing.
the kiln jumps in heat. there is no smoke at the top of the
stack, in fact, there is never smoke at my stack...only heat
waves. now i have to slow it down...or the cones will
just go over fast. i milk it for an hour.
when cone 11 is half way down...i shut off the kiln.
i let the kiln cool until it is at 1900f, and then turn back on
one burner. i hold the kiln at 1900 for two hours. (plus or minus
depending on the glazes in the kiln.)
if i am firing all copper red, i let the kiln drop to about 1700f
and then turn it back on and fire in oxy til i hit about 2000f.
then let it cool for 28 hours.
open slowly. one brick at a time.
that takes about 5 more hours.
pots come out when i can touch them with a cotton jersey glove on my hands.
unload.
the total time for a 45 cubic foot kiln is 10-11 hours...depending
on weather , wind etc.
we should have about 98 percent perfect pots.
my front low is a hot spot in my kiln. so, i fire low bowls with
red glaze....and they do all sorts of wonderful things...like purple,
red, blue and whatever. they are often the first pots to sell...about
cone 12 is my guess.
we basically use this same system at the farm...and that little
flat top fires in 4-5 hours. it is a speed kiln as we fire it every day
for almost two weeks. it sure gives us great pots. no one ever
complains. some think firing that fast if blasphemy...well, it
is my kiln, my technique and only i have control (well, bob anderson
bullies me.) we love that little speedie baby kiln. and, to make folks
even more crazy...we often fire in oxy all the way, and reduce
on the way down. just for fun...and the pots are always perfectly
reduced. another myth broken.
mel
http://www.visi.com/~melpots/
clayart page below:
http://www.visi.com/~melpots/clayart.html
ivor and olive lewis on fri 16 mar 12
Dear Mel,
A lot of wisdom in what you say but there is nothing that would assist
someone who has never had the privilege of meeting and learning from either
of us.
Three decades ago I took up an appointment. I teemed up with one of my new
colleagues who had joined me for a course relating to studio practice at
the nearby community college (Round trip 110 Km).
Turned out she had a problem. Her father had built a gas kiln for her and
she was having troubles firing the beast. It refused to heat up. So she
tried to get our lecturer to visit and find a cure for the problems. He
never did. So I offered to sort things out for her. She refused but wanted
John to help.
What I would like you to do is to explain (for the benefit of lurkers and
those who are too shy to ask) how you get to know your "Let Her Rip and
Roar settings". I'm sure there is an audience out there waiting to read and
learn the A..B..Css. and the 1..2..3ss.. of Good Kiln practice
Best regards,
Ivor Lewis,
REDHILL,
South Australia
Gerholdclay on fri 16 mar 12
The question of energy waste in industry is not quite as simple as you want=
t=3D
o make it. Capital projects " spending on equipment etc" to reduce energ=
y=3D
use are governed by the same payback rules as most other capital projects=
.=3D
If the savings to pay for the spending can be achieved in a certain numbe=
r=3D
of years the project goes foreward, if not the money is spent elsewhere.
This is somewhat fudged by government subsidies but in general is still tru=
e=3D
. As Energy prices increase the payback time decreases so higher energy pr=
i=3D
ces do encourage conservation.=3D20
This applies to most of us as well. I could get a more efficient car but i=
t=3D
would not pay for itself for about twelve years.
Paul
Sent from my iPad
On Mar 15, 2012, at 9:53 AM, mel jacobson wrote:
> i was up early (four a.m.) firing my kiln.
> i have posted this before, but as long as we
> have pdf's flying across the world with kiln plans,
> it is good to insert some ideas about the `process of firing`,
> not kiln architecture.
>=3D20
> for years the wisdom was always about slow early firing.
> in fact many will fire for hours with one burner on half power.
> the kiln just fired slow and slower. `gotta go slow you know`..why?
> or, even all night candle with one burner.
>=3D20
> it is mostly total bs.
>=3D20
> if you have well fired bisque, and your glazes are dry, fire your
> kiln with full power right off the bat. why the slow?
>=3D20
> you want to build energy in your kiln, as fast as you can.
> get the energy into the kiln...and that would be heat.
>=3D20
> as you fire the kiln heat moves through the brick and leaks
> out into the room. that is natural.
> but, as the heat leaves the kiln, so does the insulating property
> of the brick. the longer your early firing, the more you lose
> insulation. that is the K factor of your brick.
> so: what does a long early, slow firing do for you? costs you
> fuel, money, time and the kiln and pots do not care.
> and, at a time when fuel costs and ecology is front and center,
> why waste it on theory that is 90 years old?
>=3D20
> fire for speed and proper balance. and balance and rhythm are
> front and center.
> you feel the firing, you sense things with experience, you
> can hear the kiln, smell the kiln, feel the kiln.
>=3D20
> for example. if your kiln is spewing flame from the stack,
> you have an 18 inch flame from the peep hole when you
> check the cones....you have an outrageous firing going on.
> most of your fuel is warming the atmosphere. nothing is
> staying in the kiln.....and what you are heating, should be inside
> the kiln. not the outside.
>=3D20
> i fire my kiln with a 40 foot gas line from my house to my garage.
> one and half inch black pipe, buried. it has been underground
> for almost 50 years. it attaches to my house meter.
> all the conventional wisdom says: `that will not work, not near
> enough gas pressure, it will not work`...well, it does, and has
> for thousands of firings.
>=3D20
> many kilns fire with far too much pressure, not too little.
> (i can't tell you how much time and energy i have spent
> traveling fixing kilns, helping folks.) in most cases the
> kiln is fine...they just `over fire`. hit the gas pedal to
> the floor and heat the outside world. i fire the kiln with
> half the gas, in half the time, with much better glazes
> from the kiln. of course, the glazes are brighter, not
> so heavily reduced, and, often the potter does not see the
> `better quality`...they are used to over fired, over reduced pots.
>=3D20
> i have no issues with professional potters that have a system in
> place for their work. that is their business, and if it works for them..
> fine. they know what they are doing...and have a background
> to rely on. if your glazes need time, so be it. that is up to the
> potter in charge.
>=3D20
> i just hate waste and ignorance of basic thermo/dynamics and
> the in your face....`we have always done it this way`.
>=3D20
> and that is the problem, never change, live in 1930, but
> they will hit you in the face if you throw a soda can away.
> but, they just wasted fuel by the ton, and heated the world
> at large...they just did not understand it. ecologist with
> no brain in place...just platitudes. and then they tell you
> that industry wastes gas and electricity...are you kidding??.
> when your gas bill is two million dollars a year, do you
> think they waste it...???? engineers plot every btu, every
> ounce, every amp. companies go to great lengths to
> conserve every ounce of energy. if not, profit goes out
> the window.
>=3D20
> almost everything we use and buy is heat treated. metal, plastic,
> wood, even paper. the product is tempered with heat. it has
> to be controlled to perfection. no waste.
>=3D20
> if more potters looked at industry and sought information
> about gas, fire, heat and energy, we would have better pots.
> and, we would not waste very much.
>=3D20
> this is how i fire...every time:
> i leave a tiny burner on over night...it is like a big pilot.
> it warms the kiln, pots and furniture/advancers to about
> 400F. like your home oven. the wax melts and the stack
> warms. heat is building, but the brick is cold.
>=3D20
> i open my flue/damper and heat it with a burnzomatic torch and watch
> the heat go up...as in up the chimney. now the gas/heat
> is going in the right direction.
> i turn on both of my burners to `full`.
> i hit it.
>=3D20
> when the kiln reaches 1700f i turn the kiln down 1/3rd.
> i slide in the damper so that about two inches of soft flame
> comes from my main peep, halfway up the kiln front.
> as the kiln reaches 2100f, i turn the burners down to half.
> at 2200f i turn it down to only a fourth of the gas is flowing.
> the kiln jumps in heat. there is no smoke at the top of the
> stack, in fact, there is never smoke at my stack...only heat
> waves. now i have to slow it down...or the cones will
> just go over fast. i milk it for an hour.
> when cone 11 is half way down...i shut off the kiln.
>=3D20
> i let the kiln cool until it is at 1900f, and then turn back on
> one burner. i hold the kiln at 1900 for two hours. (plus or minus
> depending on the glazes in the kiln.)
> if i am firing all copper red, i let the kiln drop to about 1700f
> and then turn it back on and fire in oxy til i hit about 2000f.
> then let it cool for 28 hours.
> open slowly. one brick at a time.
> that takes about 5 more hours.
> pots come out when i can touch them with a cotton jersey glove on my hand=
s=3D
.
> unload.
>=3D20
> the total time for a 45 cubic foot kiln is 10-11 hours...depending
> on weather , wind etc.
>=3D20
> we should have about 98 percent perfect pots.
>=3D20
> my front low is a hot spot in my kiln. so, i fire low bowls with
> red glaze....and they do all sorts of wonderful things...like purple,
> red, blue and whatever. they are often the first pots to sell...about
> cone 12 is my guess.
>=3D20
> we basically use this same system at the farm...and that little
> flat top fires in 4-5 hours. it is a speed kiln as we fire it every day
> for almost two weeks. it sure gives us great pots. no one ever
> complains. some think firing that fast if blasphemy...well, it
> is my kiln, my technique and only i have control (well, bob anderson
> bullies me.) we love that little speedie baby kiln. and, to make folks
> even more crazy...we often fire in oxy all the way, and reduce
> on the way down. just for fun...and the pots are always perfectly
> reduced. another myth broken.
> mel
>=3D20
>=3D20
>=3D20
>=3D20
>=3D20
>=3D20
>=3D20
> http://www.visi.com/~melpots/
> clayart page below:
> http://www.visi.com/~melpots/clayart.html
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