Larry Kruzan on tue 20 sep 11
Could I write a book of this one! Oh - wait a minute, Mel did already. Oh
well.
For the past 7 years I have been working as a production potter churning ou=
t
a small line with a eye of costs and the bottom line. There were a few
fundamental points that I'd like to throw into the mix;
Point One - Mel is right! Repeat three times, bow head and ask forgiveness.
Open eyes, shut mouth and learn.
Point two - First day back at the university and I'm meeting the other grad
students. Introduced to a young lady, in her late twenties who is in her
final year. As we get to know each other she is setting up a large bailey
front loader electric kiln, she begins to program it and I see that she is
doing bisque with a 24 hour soak at 300 degrees! I saw the work that went i=
n
the kiln and it was light functional ware that had been drying for two
weeks. When I asked about her program, she informed me that she always did =
a
bisque firing over three DAYS!!!! When I asked about energy cost and waste,
she told me point blank that she did not pay the bill and could care less -
All this was done as she was hurrying to get to some "save the environment
green rally". Good greif!
Point three - Since I was there for my undergrad work, a new, small, IFB
kiln has been built. Very, very nice construction and a perfect size for
fast turnaround and quick feedback. Single forced air burner a properly
sized flue should make it easy to fire Monday and unload Tuesday afternoon.
Is that how it will be fired - nope. Fill Prof (good kid but no life
experience) is going to do a 24 hour "candle" today and fire on up tomorrow
like it was the 100cf hardbrick kiln sitting beside it.
Point Four - materials. I asked about getting some tin oxide for my glazes =
-
first statement out of the mouth was, "Isn't that poisonous?". They are
concerned about glaze materials in the studio but there is no concern over
the totally nonfunctional "spray booth". I had the blower system running an=
d
tried to spray some glaze on a pot and so help me - I got more glaze on me
than on the pot!!! Good thing I had my mask on. When I asked how long it ha=
d
been like that, the head grad student (yes, the same one) told me "that it
was ok to just dip your work, since the spray booth was so lousy, they did
not critique on glazing - just do what everyone else does and use the salt
kiln, they love salt finishes." - but I don't just got me a shrug. My query
about the health effects on other students who do not have masks on and the
"environment" were ignored.
Point Five - Size burners for the job needed. A 100cf kiln does not need 2
1,500,000 BTU burners!! Mine fired just fine (without candling) on 2 375,00=
0
btu burners. That kiln sounds like a F18 spooled up for a catapult shot on
an aircraft carrier. I was informed that the engineering dept of the
university specd out the burner requirements for the kilns there - who dumb
idea was THAT and who determined that they knew more about making pottery
than the dept?? - On second thought, maybe they do.......
Larry
*****************
several folks have sent me private emails asking about long warm-ups, or
pre-firing.
it is a total waste of fuel and time.
total waste.
<<<<<<<>>>>>>>>>>>>
`but mel, we used to do firings this way in 1960 at our college and it
worked well.` hmmm, they were dumb as bricks then too. and they still fir=
e
that way.
doing it wrong for 60 years does not make it right.
and as i say...`they will hit you in the face if you do not re/cycle your
beer can.` but, they waste millions of btu's of fuel for nothing. eco
stupid. far too much of that going on.
your tax dollars at work.
mel jacobson on tue 20 sep 11
several folks have sent me private emails
asking about long warm-ups, or pre-firing.
it is a total waste of fuel and time.
total waste.
a few hours of pre/warm with the pilots if you
are concerned with shelves, furniture in your
kiln is fine...up to maybe 350F...ok. get out the damp.
but, when you pre/heat any kiln you destroy
the K factor of your bricks.
for example. you pre'heat over night.
your kiln is at 800F in the morning.
feel the brick..hot as can be.
your insulating factor of your brick is now gone.
you are firing your kiln without the K factor of your
brick...k-23's are hot all the way through, the heat is
coming out of them. not insulating.
it is simple math.
you wasted the fuel to warm the kiln and you lost
the insulating factor for your firing. dumb as can be.
`but mel, we used to do firings this way in 1960 at our
college and it worked well.` hmmm, they were dumb as
bricks then too. and they still fire that way.
doing it wrong for 60 years does not make it right.
and as i say...`they will hit you in the face if you do not
re/cycle your beer can.` but, they waste millions of btu's
of fuel for nothing. eco stupid. far too much of that going on.
your tax dollars at work.
i have a tiny burner that is really a big pilot. i turn that on
for a few hours before i start my firing. (get the heat going up
the stack)
now the kiln is warm, pots are warm...275F, so i turn on my
burners full. get the flame as blue as sky. build energy in the
kiln as fast as i can. the more you build, the hotter the kiln gets.
use the damper at 1750 to start a small three inch flame from
your middle peep. as the kiln moves to 2000F the flame will
grow from the peep, and the kiln may start to just stall a bit.
then start to reduce the amount of gas. turn it down to 3/4 gas
pressure, then keep observing...and turn it down more. adjust the
damper accordingly.
the kiln will jump in temp. when i finish my firing my burners
are turned down about 75 percent. cones drop like stones.
i like to call it `building heat energy as fast as you can.`
when that energy fills the kiln, turn down your burners.
my big 45 cubic foot kiln fires consistently in 9 hours.
about 90 pots per firing. no waste of fuel.
the kiln walls are still cool when i start reduction...at the
end of the firing i can still put my hands on the kiln.
three hours after the kiln is off...the bricks are hot as hell.
mel
from: minnetonka, mn
website: http://www.visi.com/~melpots/
clayart link: http://www.visi.com/~melpots/clayart.html
Liz Gowen 1 on tue 20 sep 11
Mel this is what I have been looking for, I do just about stall at about
2000F, I will try decreasing the gas on the next firing
Thanks ..Liz Gowen
i have a tiny burner that is really a big pilot. i turn that on for a few
hours before i start my firing. (get the heat going up the stack) now the
kiln is warm, pots are warm...275F, so i turn on my burners full. get the
flame as blue as sky. build energy in the kiln as fast as i can. the more
you build, the hotter the kiln gets.
use the damper at 1750 to start a small three inch flame from your middle
peep. as the kiln moves to 2000F the flame will grow from the peep, and th=
e
kiln may start to just stall a bit.
then start to reduce the amount of gas. turn it down to 3/4 gas pressure,
then keep observing...and turn it down more. adjust the damper accordingly=
.
the kiln will jump in temp. when i finish my firing my burners are turned
down about 75 percent. cones drop like stones.
mel
from: minnetonka, mn
website: http://www.visi.com/~melpots/
clayart link: http://www.visi.com/~melpots/clayart.html
Liz Gowen 1 on wed 21 sep 11
I had gone to a group Raku firing several weeks ago that we have had every
year for over 12 years. There were several elementary school teachers at
this one, and I overheard them talking about their firing schedules for an
electric kiln, very long manual schedules. The one that really floored me
was the potter at whose house we have it. She always fired gas in the past
but just got a used electric kiln. Apparently it has dials with infinite
settings so she feels she has to leave it on 1 hour for each increment. I
told her on the manual I had I had always done bisque at 2 hours low 2 med
then crank it up. She refused to believe me and said why would they put all
those increments on if it wasn't meant to be fired her way. I tried to
explain how they would be useful for slow cooling a glaze firing but she an=
d
the other teachers were not buying it. How was it ok for her to fire much
faster in gas but to follow this schedule for electric????..Liz Gowen
Larry wrote
Point two - First day back at the university and I'm meeting the other grad
students. Introduced to a young lady, in her late twenties who is in her
final year. As we get to know each other she is setting up a large bailey
front loader electric kiln, she begins to program it and I see that she is
doing bisque with a 24 hour soak at 300 degrees! I saw the work that went i=
n
the kiln and it was light functional ware that had been drying for two
weeks. When I asked about her program, she informed me that she always did =
a
bisque firing over three DAYS!!!! When I asked about energy cost and waste,
she told me point blank that she did not pay the bill and could care less -
All this was done as she was hurrying to get to some "save the environment
green rally". Good greif!
Point three - Since I was there for my undergrad work, a new, small, IFB
kiln has been built. Very, very nice construction and a perfect size for
fast turnaround and quick feedback. Single forced air burner a properly
sized flue should make it easy to fire Monday and unload Tuesday afternoon.
Is that how it will be fired - nope. Fill Prof (good kid but no life
experience) is going to do a 24 hour "candle" today and fire on up tomorrow
like it was the 100cf hardbrick kiln sitting beside it.
Point Four - materials. I asked about getting some tin oxide for my glazes =
-
first statement out of the mouth was, "Isn't that poisonous?". They are
concerned about glaze materials in the studio but there is no concern over
the totally nonfunctional "spray booth". I had the blower system running an=
d
tried to spray some glaze on a pot and so help me - I got more glaze on me
than on the pot!!! Good thing I had my mask on. When I asked how long it ha=
d
been like that, the head grad student (yes, the same one) told me "that it
was ok to just dip your work, since the spray booth was so lousy, they did
not critique on glazing - just do what everyone else does and use the salt
kiln, they love salt finishes." - but I don't just got me a shrug. My query
about the health effects on other students who do not have masks on and the
"environment" were ignored.
Point Five - Size burners for the job needed. A 100cf kiln does not need 2
1,500,000 BTU burners!! Mine fired just fine (without candling) on 2 375,00=
0
btu burners. That kiln sounds like a F18 spooled up for a catapult shot on
an aircraft carrier. I was informed that the engineering dept of the
university specd out the burner requirements for the kilns there - who dumb
idea was THAT and who determined that they knew more about making pottery
than the dept?? - On second thought, maybe they do.......
Larry
Arnold Howard on wed 21 sep 11
On 9/21/2011 7:33 AM, Liz Gowen 1 wrote:
She always fired gas in the past
> but just got a used electric kiln. Apparently it has dials with infinite
> settings so she feels she has to leave it on 1 hour for each increment. =
I
> told her on the manual I had I had always done bisque at 2 hours low 2 me=
d
> then crank it up. She refused to believe me and said why would they put a=
ll
> those increments on if it wasn't meant to be fired her way.
This is why Clayart is valuable. Imagine how much time people can save
by coming here and asking questions. A single piece of information,
which may at first seem insignificant, can cut fuel cost in half, or
double production, or improve sales.
I attended an enameling conference last weekend and met an artist who
taught torch-fired enameling. He flew in all the way from Australia to
share an idea that others consider revolutionary. He discovered that
merely changing the amount of oxygen in the flame vastly altered the
enameling. He flew in from Australia to teach that one idea.
Sincerely,
Arnold Howard
Paragon Industries, L.P., Mesquite, Texas USA
ahoward@paragonweb.com / www.paragonweb.com
Snail Scott on wed 21 sep 11
On Sep 21, 2011, at 7:33 AM, Liz Gowen 1 wrote:
> ... it has dials with infinite
> settings so she feels she has to leave it on 1 hour for each increment. =
I
> told her on the manual I had I had always done bisque at 2 hours low 2 me=
d
> then crank it up. She refused to believe me and said why would they put a=
ll
> those increments on if it wasn't meant to be fired her way....
If the knob on my kiln says "11" that means it gets
hotter than those kilns that only say '10', right? ;)
-Snail
Steve Mills on thu 22 sep 11
So when were you a member of Spinal Tap?
:-)
Steve Mills
Bath
UK
www.mudslinger.me.uk
Sent from my Ipod touch
On 21 Sep 2011, at 18:52, Snail Scott wrote:
> If the knob on my kiln says "11" that means it gets
> hotter than those kilns that only say '10', right? ;)
>
> -Snail
C. Tullis on thu 22 sep 11
Hey Larry, don't hold back, just say what you mean.... Good post.
ivor and olive lewis on mon 26 sep 11
It seems to me that there is a lot of conjecture associated with our
understanding of the thermal behaviour of a kiln. What is important is the
differential between the temperature of the ware being fired, the
temperature of the atmosphere, the temperature on the inner face of the
refractories, the temperature of the outer face of the refractories and the
ambient temperature of your kiln shed.
Mel tells us ....when you pre/heat any kiln you destroy the K factor of you=
r
bricks.... What does this mean ? What evidence is there ? How can you
eliminate physical properties of matter ?
Since "K" factors are a measure of thermal energy conduction through
materials they are directly related to the temperature difference between
the hot and the cold faces. As temperature difference diminishes energy flo=
w
decelerates, eventually equilibrating.
The phenomena of fire would be better understood if it were examined under
experimental conditions with pyrometers measuring temperatures at salient
locations within and outside the kiln.
Strange though it may seem, having a single refractory substance as an
insulator is far less economic than constructing kiln walls from layers of
refractories having progressively lower "K" factors moving to the outer
wall.. This restricts heat flow causing the inner wall to heat up until it
is almost as hot as the interior face. When both are at the same temperatur=
e
heat loss is reduced to a minimum.
Which is why, when I started designing my kilns some thirty years ago, I
incorporated several layers of refractory both for Hard brick and Fibre
lined kilns.
Best regards,
Ivor Lewis,
REDHILL,
South Australia
paul gerhold on mon 26 sep 11
Dear Ivor,
The heat loss from a kiln is solely determined by the temperature
differential between the surface of the kiln and the air temp immediately
next to the kiln. Heat transfer from the inner wall of the kiln to the
outer surface is (simplifying considerably) a function of the overall heat
transfer coefficient of the kiln wall which is a weighted average of the
heat transfer coefficients of the materials used.
Thus six inches of fiber kiln will lose a lot less heat than six inches of
hard brick. Three inches of fiber and three inches of hard brick will be
somewhere in between the two.Kiln builders use a combination for the
strength and durability of the hard brick and the low heat transfer
coefficient of the fibre.
Bottom line if you want to save energy is fire in the desert on a day that
is not windy and fire fast.
Paul
On Mon, Sep 26, 2011 at 1:42 AM, ivor and olive lewis u
> wrote:
> It seems to me that there is a lot of conjecture associated with our
> understanding of the thermal behaviour of a kiln. What is important is th=
e
> differential between the temperature of the ware being fired, the
> temperature of the atmosphere, the temperature on the inner face of the
> refractories, the temperature of the outer face of the refractories and t=
he
> ambient temperature of your kiln shed.
> Mel tells us ....when you pre/heat any kiln you destroy the K factor of
> your
> bricks.... What does this mean ? What evidence is there ? How can you
> eliminate physical properties of matter ?
> Since "K" factors are a measure of thermal energy conduction through
> materials they are directly related to the temperature difference between
> the hot and the cold faces. As temperature difference diminishes energy
> flow
> decelerates, eventually equilibrating.
> The phenomena of fire would be better understood if it were examined unde=
r
> experimental conditions with pyrometers measuring temperatures at salient
> locations within and outside the kiln.
> Strange though it may seem, having a single refractory substance as an
> insulator is far less economic than constructing kiln walls from layers o=
f
> refractories having progressively lower "K" factors moving to the outer
> wall.. This restricts heat flow causing the inner wall to heat up until i=
t
> is almost as hot as the interior face. When both are at the same
> temperature
> heat loss is reduced to a minimum.
> Which is why, when I started designing my kilns some thirty years ago, I
> incorporated several layers of refractory both for Hard brick and Fibre
> lined kilns.
> Best regards,
> Ivor Lewis,
> REDHILL,
> South Australia
>
ivor and olive lewis on tue 27 sep 11
Dear Paul,
Your simplistic assessment is something I implied in my opening =3D
statement. Fuel Efficiency is solved by designing a integrated system =3D
from the range of materials available.=3D20
In the Desert my best firings are those that happen when the humidity is =
=3D
at a maximum.
If a potter wishes to cool slowly which is the most fuel efficient, Fire =
=3D
Down or make the interior lining of a projected kiln from dense =3D
refractory bricks.
Ivor
----- Original Message -----=3D20
From: paul gerhold=3D20
To: ivor and olive lewis=3D20
Cc: =3D20
Sent: Tuesday, September 27, 2011 2:48 AM
Subject: Re: k-factor in firing
Dear Ivor,
The heat loss from a kiln is solely determined by the temperature =3D
differential between the surface of the kiln and the air temp =3D
immediately next to the kiln. Heat transfer from the inner wall of the =3D
kiln to the outer surface is (simplifying considerably) a function of =3D
the overall heat transfer coefficient of the kiln wall which is a =3D
weighted average of the heat transfer coefficients of the materials =3D
used. =3D20
Thus six inches of fiber kiln will lose a lot less heat than six =3D
inches of hard brick. Three inches of fiber and three inches of hard =3D
brick will be somewhere in between the two.Kiln builders use a =3D
combination for the strength and durability of the hard brick and the =3D
low heat transfer coefficient of the fibre.
Bottom line if you want to save energy is fire in the desert on a day =3D
that is not windy and fire fast.
Paul
On Mon, Sep 26, 2011 at 1:42 AM, ivor and olive lewis =3D
wrote:
It seems to me that there is a lot of conjecture associated with our
understanding of the thermal behaviour of a kiln. What is important =3D
is the
differential between the temperature of the ware being fired, the
temperature of the atmosphere, the temperature on the inner face of =3D
the
refractories, the temperature of the outer face of the refractories =3D
and the
ambient temperature of your kiln shed.
Mel tells us ....when you pre/heat any kiln you destroy the K factor =
=3D
of your
bricks.... What does this mean ? What evidence is there ? How can =3D
you
eliminate physical properties of matter ?
Since "K" factors are a measure of thermal energy conduction through
materials they are directly related to the temperature difference =3D
between
the hot and the cold faces. As temperature difference diminishes =3D
energy flow
decelerates, eventually equilibrating.
The phenomena of fire would be better understood if it were examined =
=3D
under
experimental conditions with pyrometers measuring temperatures at =3D
salient
locations within and outside the kiln.
Strange though it may seem, having a single refractory substance as =3D
an
insulator is far less economic than constructing kiln walls from =3D
layers of
refractories having progressively lower "K" factors moving to the =3D
outer
wall.. This restricts heat flow causing the inner wall to heat up =3D
until it
is almost as hot as the interior face. When both are at the same =3D
temperature
heat loss is reduced to a minimum.
Which is why, when I started designing my kilns some thirty years =3D
ago, I
incorporated several layers of refractory both for Hard brick and =3D
Fibre
lined kilns.
Best regards,
Ivor Lewis,
REDHILL,
South Australia
paul gerhold on tue 27 sep 11
Dear Ivor,
The answer is none of the above. The most efficient kiln is the on that
loses the lest heat to the environment period. Hard brick fires down slowl=
y
because you have wasted a great deal of energy heating the hard brick on th=
e
way up.
Build a kiln with vacuum insulated walls and you will fire very fast on the
way up and you will cool down very slowly.
Paul
On Tue, Sep 27, 2011 at 12:37 AM, ivor and olive lewis <
iandol@westnet.com.au> wrote:
> **
> Dear Paul,
> Your simplistic assessment is something I implied in my opening
> statement. Fuel Efficiency is solved by designing a integrated system fro=
m
> the range of materials available.
> In the Desert my best firings are those that happen when the humidity is =
at
> a maximum.
> If a potter wishes to cool slowly which is the most fuel efficient, Fire
> Down or make the interior lining of a projected kiln from dense refractor=
y
> bricks.
>
> Ivor
>
>
> ----- Original Message -----
> *From:* paul gerhold
> *To:* ivor and olive lewis
> *Cc:*
> *Sent:* Tuesday, September 27, 2011 2:48 AM
> *Subject:* Re: k-factor in firing
>
> Dear Ivor,
> The heat loss from a kiln is solely determined by the temperature
> differential between the surface of the kiln and the air temp immediately
> next to the kiln. Heat transfer from the inner wall of the kiln to the
> outer surface is (simplifying considerably) a function of the overall hea=
t
> transfer coefficient of the kiln wall which is a weighted average of the
> heat transfer coefficients of the materials used.
>
> Thus six inches of fiber kiln will lose a lot less heat than six inches o=
f
> hard brick. Three inches of fiber and three inches of hard brick will be
> somewhere in between the two.Kiln builders use a combination for the
> strength and durability of the hard brick and the low heat transfer
> coefficient of the fibre.
>
> Bottom line if you want to save energy is fire in the desert on a day tha=
t
> is not windy and fire fast.
>
> Paul
>
> On Mon, Sep 26, 2011 at 1:42 AM, ivor and olive lewis <
> iandol@westnet.com.au> wrote:
>
>> It seems to me that there is a lot of conjecture associated with our
>> understanding of the thermal behaviour of a kiln. What is important is t=
he
>> differential between the temperature of the ware being fired, the
>> temperature of the atmosphere, the temperature on the inner face of the
>> refractories, the temperature of the outer face of the refractories and
>> the
>> ambient temperature of your kiln shed.
>> Mel tells us ....when you pre/heat any kiln you destroy the K factor of
>> your
>> bricks.... What does this mean ? What evidence is there ? How can you
>> eliminate physical properties of matter ?
>> Since "K" factors are a measure of thermal energy conduction through
>> materials they are directly related to the temperature difference betwee=
n
>> the hot and the cold faces. As temperature difference diminishes energy
>> flow
>> decelerates, eventually equilibrating.
>> The phenomena of fire would be better understood if it were examined und=
er
>> experimental conditions with pyrometers measuring temperatures at salien=
t
>> locations within and outside the kiln.
>> Strange though it may seem, having a single refractory substance as an
>> insulator is far less economic than constructing kiln walls from layers =
of
>> refractories having progressively lower "K" factors moving to the outer
>> wall.. This restricts heat flow causing the inner wall to heat up until =
it
>> is almost as hot as the interior face. When both are at the same
>> temperature
>> heat loss is reduced to a minimum.
>> Which is why, when I started designing my kilns some thirty years ago, I
>> incorporated several layers of refractory both for Hard brick and Fibre
>> lined kilns.
>> Best regards,
>> Ivor Lewis,
>> REDHILL,
>> South Australia
>>
>
>
ivor and olive lewis on wed 28 sep 11
Dear Paul Gerhold,
I am wondering if, in changing from an atmospheric system to an ultra low
pressure system, you are moving the goalposts. Since the mode of energy
dissipation is changed new rules apply.
Regards,
Ivor Lewis,
REDHILL,
South Australia
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