Nils Lou on wed 13 jan 10
A reasonable question, DF. I could have left out "plasma mass", but
it sounds real scientific; and if I had left it out you probably
wouldn't have jumped on it.
In a combustion product of heated gases there is a plasma aspect of
ionized gas that is electrically conductive. It is this plasma that
conducts electrons to complete an electric circuit in burner safety
systems. No combustion, no plasma, burner shuts down. Yeah, plasma=3D20
is a unique state of being--like the soul of combustion...well, maybe =3D
not.
As for electric kilns, not to worry. It's just heated air, not =3D
combustion
products. So no plasma stuff to be concerning. nils
nils lou, professor of art
http://nilslou.blogspot.com
www.tinyurl.com/bpc5nm
503.883.2274
"Play is the essence of creativity", and
"What is not brought forward into consciousness....
we later call Fate", Carl Jung
-----Original Message-----
From: douglas fur [mailto:23drb50@gmail.com]
Sent: Wed 1/13/2010 7:44 PM
To: Nils Lou
Cc: Clayart@lsv.ceramics.org
Subject: Re: Ingeborg's kiln and "Null Points"
=3D20
OK Nils Lou- 'splain this one to me...
"It is a function of *plasma mass* of heated gases affected by friction
causing a pulsing in rate of vertical movement."
It seems like the phrase *plasma mass* could be left out and your =3D
statement
would be as valid.
In a quick wikipedia search I found fire mentioned as a source of =3D
plasmas
but no clear explaination of how they're formed. the general def of =3D
plasma
1. *Physics*. An electrically neutral, highly ionized gas composed of
ions, electrons, and neutral particles. It is a phase of matter =3D
distinct
from solids, liquids, and normal gases.
sounds like a different order of business than what we see in a kiln.
Another statement from WkPDA "The presence of a non-negligible number of
charge carriers makes the plasma electrically
conductive"
sounds like touble in an electric kiln...
DRB
Seattle
steve graber on wed 13 jan 10
thanks nils, i needed that.=3DC2=3DA0 i thought i needed to raise my stack =
some=3D
but other than swagging (silly wild ass guessing) how much higher to raise=
=3D
it i will raise it about 18 inches to start.=3DC2=3DA0 i have a downdraft =
arch=3D
kiln, natural gas.=3DC2=3DA0 the door admittedly needs more sealing work.=
=3DC2=3D
=3DA0 but the flew draft is also a problem.=3DC2=3DA0 =3D0A=3D0A=3D0A=3DC2=
=3DA0Steve Graber=3D
, Graber's Pottery, Inc=3D0AClaremont, California USA=3D0AThe Steve Tool - =
for =3D
awesome texture on pots! =3D0Awww.graberspottery.com steve@graberspottery.c=
om=3D
=3D0A=3D0A=3D0AOn Laguna Clay's website=3D0Ahttp://www.lagunaclay.com/blog=
s/ =3D0A=3D
=3D0A=3D0A=3D0A----- Original Message ----=3D0A> From: Nils Lou ELD.EDU>=3D
=3D0A> To: Clayart@LSV.CERAMICS.ORG=3D0A> Sent: Wed, January 13, 2010 9:58:=
08 A=3D
M=3D0A> Subject: Ingeborg's kiln and "Null Points"=3D0A> =3D0A> Null points=
in ki=3D
ln stacks occur as a periodicity in the rate of exhaust flow. =3D0A> It is =
a =3D
function of plasma mass of heated gases affected by friction causing a =3D0=
A>=3D
pulsing in rate of vertical movement. Imagine water flowing in a stream be=
=3D
d as =3D0A> it moves rapidly in one place and=3DC2=3DA0 slowly where there =
are ro=3D
cks and weeds. You =3D0A> can see it swirling and even reversing as it move=
s.=3D
=3D0A> In a stack, gravity actually pushes the exhaust up and out because =
of=3D
the weight =3D0A> and pressure of heavier gases in the kiln. Generally, th=
e =3D
higher the stack, the =3D0A> faster the exhaust flow=3DE2=3D80=3D94=3DC2=3D=
A0 up to a p=3D
oint. As the exhaust cools it gets heavier, =3D0A> so there is a point of b=
es=3D
t efficiency in stack height for any given situation. =3D0A> There are also=
h=3D
eights where if they coincide at the top with a null point the =3D0A> effec=
t =3D
may be the same as a negative damper. Also, remember, the null point is a =
=3D
=3D0A> moving target as it is a function of temperature and friction in the=
s=3D
tack, and =3D0A> temperature in the kiln. A common stall point is 1900=3DC2=
=3DB0 =3D
F in a lot of kilns. My =3D0A> contention is that the dampering effect is f=
ro=3D
m the null point moving to the top =3D0A> of the stack where it effectively=
s=3D
lows the drafting. There is a Venturi effect =3D0A> as gases exit the stack=
a=3D
nd expand. If this is interrupted by the null point at =3D0A> the point of =
ex=3D
it, the Venturi effect is diminished. =3D0A> So, by changing the stack heig=
ht=3D
up or down by 18 inches or so this problem can =3D0A> be solved. Homemade =
ki=3D
lns can start with expert recommendations, but will need a =3D0A> trial and=
e=3D
rror to find the best functioning stack. In Ingeborg=3DE2=3D80=3D99s case m=
oving =3D
=3D0A> her kiln from Camas, Washington to Florida involved an elevation cha=
ng=3D
e of 1000 =3D0A> feet or so. So, at sea level, a shorter stack might well b=
e =3D
the answer. This =3D0A> discussion refers to downdraft kilns only, as an up=
dr=3D
aft design does not =3D0A> function the same way. =3D0A> =3D0A> =3D0A> nils=
lou, pr=3D
ofessor of art=3D0A> http://nilslou.blogspot.com=3D0A> www.tinyurl.com/bpc5=
nm=3D
=3D0A> 503.883.2274=3D0A> "Play is the essence of creativity", and=3D0A> "W=
hat is=3D
not brought forward into consciousness....=3D0A> we later call Fate", Carl=
J=3D
ung=3D0A=3D0A=3D0A=3D0A
douglas fur on wed 13 jan 10
OK Nils Lou- 'splain this one to me...
"It is a function of *plasma mass* of heated gases affected by friction
causing a pulsing in rate of vertical movement."
It seems like the phrase *plasma mass* could be left out and your statement
would be as valid.
In a quick wikipedia search I found fire mentioned as a source of plasmas
but no clear explaination of how they're formed. the general def of plasma
1. *Physics*. An electrically neutral, highly ionized gas composed of
ions, electrons, and neutral particles. It is a phase of matter distinct
from solids, liquids, and normal gases.
sounds like a different order of business than what we see in a kiln.
Another statement from WkPDA "The presence of a non-negligible number of
charge carriers makes the plasma electrically
conductive"
sounds like touble in an electric kiln...
DRB
Seattle
Nils Lou on wed 13 jan 10
Null points in kiln stacks occur as a periodicity in the rate of exhaust =
=3D
flow. It is a function of plasma mass of heated gases affected by =3D
friction causing a pulsing in rate of vertical movement. Imagine water =3D
flowing in a stream bed as it moves rapidly in one place and slowly =3D
where there are rocks and weeds. You can see it swirling and even =3D
reversing as it moves.=3D20
In a stack, gravity actually pushes the exhaust up and out because of =3D
the weight and pressure of heavier gases in the kiln. Generally, the =3D
higher the stack, the faster the exhaust flow=3D97 up to a point. As the =
=3D
exhaust cools it gets heavier, so there is a point of best efficiency in =
=3D
stack height for any given situation. There are also heights where if =3D
they coincide at the top with a null point the effect may be the same as =
=3D
a negative damper. Also, remember, the null point is a moving target as =3D
it is a function of temperature and friction in the stack, and =3D
temperature in the kiln. A common stall point is 1900=3DB0 F in a lot of =
=3D
kilns. My contention is that the dampering effect is from the null point =
=3D
moving to the top of the stack where it effectively slows the drafting. =3D
There is a Venturi effect as gases exit the stack and expand. If this is =
=3D
interrupted by the null point at the point of exit, the Venturi effect =3D
is diminished.=3D20
So, by changing the stack height up or down by 18 inches or so this =3D
problem can be solved. Homemade kilns can start with expert =3D
recommendations, but will need a trial and error to find the best =3D
functioning stack. In Ingeborg=3D92s case moving her kiln from Camas, =3D
Washington to Florida involved an elevation change of 1000 feet or so. =3D
So, at sea level, a shorter stack might well be the answer. This =3D
discussion refers to downdraft kilns only, as an updraft design does not =
=3D
function the same way.=3D20
nils lou, professor of art
http://nilslou.blogspot.com
www.tinyurl.com/bpc5nm
503.883.2274
"Play is the essence of creativity", and
"What is not brought forward into consciousness....
we later call Fate", Carl Jung
Ingeborg Foco on thu 14 jan 10
"Null Points" as explained by Nils makes sense. Shane, Dave F, Nils and
others have mentioned that exterior effects i.e. walls trees roof lines or
other interferences have little if any effect on the draw. I still have a
hard time understanding or believing that since my personal experience was
different but I defer to you.
I would agree with Dave that stacks are not necessarily needed. My first
kiln, a prefab down draft had no stack whatsoever. it had two tiles that
you manipulated to open or close the damper so to speak. It worked.
I think Nils suggestion of removing the cap is certainly easy enough to do
(well sort, I still have to climb up on the roof and reach the top, not tha=
t
easy for a vertically challenged person.) As a long term solution it
probably isn't the best. Every time we get one of those quick 50 mph storm=
s
in the summer we also get anywhere from 1 to 3 inches of water. My stack
and the bottom of the flue will be filled with water. I'm really not makin=
g
up these severe weather conditions. The weather at times is primordial.
Summers in particular are scary.
50 mph winds happen 2 or three times a month during the summer and they
generally carry torrents of water. Those are not that scary but the
accompanying lightening storms are. At times, the streets are flooded to
the point where you cannot see the pavement, all is under water. Three
hours later, most everything has disappeared. It is quite amazing.
Removing part of the stack is an option but I will have to check whether it
will still be legal. I have a metal roof so it probably isn't super
critical but I agree with Dave that stacks should clear all roof lines.
When I moved and installed this kiln here in Florida, Kenny Simpson told me
adding the additional 3 ft pipe would make things worse as far as evening
out the temps. Kenny built the kiln originally and periodically calls me t=
o
chit chat especially to see if we are OK after a hurricane. I'm certain yo=
u
know him Nils.
Now, I can't believe I am actually entertaining messing around with my
stack. You all would make good politicians :)
If I add on, I will have to figure out how to secure it so I don't lose it.
I also will have to find someone to help me. So, that brings me to the
next question;
is it possible to fix the kiln by opening the air plates and doing some
remodeling of the bag walls? Obviously, that is something I can do without
enlisting someone else to help.
Ingeborg
douglas fur on fri 15 jan 10
NL
I think the simile of a flute or organ pipe would clarifiy your concept of
"null points" . They are like the natural octaves and other musical
intervals .
I was messing with an oil burner proto-type the other day. It made a cool
fluttering roar when I lit it but when I shifted from kerosene to
bio-diesel it changed the dynamics such that the roar stopped
You also have the experience in some cars of riding in an occarina when you
have one window just so...
DRB
Seattle
Marcia Selsor on sat 16 jan 10
If you are playing around with household oil burners (furnace) burners)
I used one back in the 70s where I put three nozzles on it with shutoff =3D
valves. The nozzles run at prescribed rates of gallons per hour. By =3D
having three varying sizes and combing them, you can adjust the BTU =3D
output and rate of increased fuel. I could send a picture of the design =3D
as published in Studio Potter Book in 1978 if you are interested.
Marcia Selsor
http://www.marciaselsor.com
On Jan 15, 2010, at 3:20 PM, douglas fur wrote:
> NL
> I think the simile of a flute or organ pipe would clarifiy your =3D
concept of
> "null points" . They are like the natural octaves and other musical
> intervals .
> I was messing with an oil burner proto-type the other day. It made a =3D
cool
> fluttering roar when I lit it but when I shifted from kerosene to
> bio-diesel it changed the dynamics such that the roar stopped
> You also have the experience in some cars of riding in an occarina =3D
when you
> have one window just so...
> DRB
> Seattle
>=3D20
gary navarre on sat 16 jan 10
Hay Folks,=3D0A=3D0A At first read I thought Nils had implied the chamber g=
asse=3D
s exited the chamber into the stack and expanded but after I re-read this I=
=3D
realized the exit you mention is from the top of the stack which makes mor=
=3D
e sense to me now. Anyway, I'm having a problem with the materials and the =
=3D
sections of metal stack that can break at the seams in high winds. I recall=
=3D
Mel saying there is nothing better than a well double bricked 9' thick chi=
=3D
mney. For one thing you can adjust the height in 2=3DBD" increments. Anothe=
r =3D
feature is you can put in a taper that keeps the gas pressure up as it rise=
=3D
s up the stack and cools before leaving the stack so the draft stays consis=
=3D
tent up the stack. I wonder if it is also possible this taper would interfe=
=3D
re with the harmonics of the straight tube and kill the null point. =3D0A=
=3D0A =3D
When I made my stack I also set a split brick on the outer course just abov=
=3D
e the sliding damper and staggered both courses to cover seams and strength=
=3D
en crossways shearing from wind. In your case I would probably encase the s=
=3D
tack in an angle iron frame and maybe guy wires and you could also add a la=
=3D
yer of red brick for more strength. A round chimney would be more aerodynam=
=3D
ic too. I left my stack at about 11-12' so far, that's as high as I can rea=
=3D
ch from the scaffold for now, with three passive damper holes up the stack,=
=3D
an active sliding damper 1/3 way up, and 16 2" holes at the top so I can p=
=3D
ut on a cap if it rains and still have somewhere for the draft to exit. =
=3D
=3D0A =3D0AGary Navarre=3D0ANavarre Pottery=3D0ANavarre Enterprises=3D0ANor=
way, Michi=3D
gan, USA=3D0Ahttp://www.youtube.com/GindaUP=3D0Ahttp://public.fotki.com/Gin=
daUP=3D
/=3D0A=3D0A=3D0A--- On Wed, 1/13/10, Nils Lou wrote:=3D=
0A=3D0A> F=3D
rom: Nils Lou =3D0A> Subject: [Clayart] Ingeborg's kiln =
an=3D
d "Null Points"=3D0A> To: Clayart@LSV.CERAMICS.ORG=3D0A> Date: Wednesday, J=
anua=3D
ry 13, 2010, 11:58 AM=3D0A> Null points in kiln stacks occur as a=3D0A> per=
iodi=3D
city in the rate of exhaust flow. It is a function of=3D0A> plasma mass of =
he=3D
ated gases affected by friction causing a=3D0A> pulsing in rate of vertical=
m=3D
ovement. =3D0A=3D0A A common stall point is 1900=3DB0 F in a lot of=3D0A> k=
ilns. My=3D
contention is that the dampering effect is from=3D0A> the null point movin=
g =3D
to the top of the stack where it=3D0A> effectively slows the drafting. Ther=
e =3D
is a Venturi effect as=3D0A> gases exit the stack and expand. If this is in=
te=3D
rrupted by=3D0A> the null point at the point of exit, the Venturi effect is=
=3D
=3D0A> diminished. =3D0A =3D0A> nils lou, professor of art=3D0A> http://nil=
slou.blo=3D
gspot.com=3D0A> www.tinyurl.com/bpc5nm=3D0A> 503.883.2274=3D0A> "Play is th=
e esse=3D
nce of creativity", and=3D0A> "What is not brought forward into consciousne=
ss=3D
....=3D0A> we later call Fate", Carl Jung=3D0A> =3D0A=3D0A=3D0A
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