mel jacobson on wed 30 sep 98
it is almost ironic that the person wrote and asked if 7 hours was too
fast to fire an electric kiln, with a warm up overnight.......(please do not
take this personally, or be embarrassed........we have all thought it.)
it amazes me that industry is firing pots in minutes now.........if the water
is gone, and they are zero dry, bingo, minutes, not hours.
it is obvious that they are balancing the glaze, clay and speed of firing.
i realize that industry runs on a different standard, the engineering is
very `use` specific.......and they sure are not doing art.
but, if they can do things in minutes, why are we still soaking electric
kilns,?
pre/heating for hours?....the glazes don't care, the kiln does not care.
but, for some reason, we care. and we waste mammoth amounts of fuel.
and yet often the same people will confess to being `green`.
we are doing a great many things that was a standard in 1930.
that is what mr. cameron is speaking to, it is what mr. barrymore is
speaking to.
and i hope we listen.
it is what nils lou has been speaking to for 20 years.
big flues, too much gas, too little gas. funny stacks, arches.........and
then
crying when the
kiln will not work. and then people argue with him when he tells them
what he thinks.
dan rhodes fought for science, understanding, progress. i like to honor him
by keeping the pressure on.
it would be a great lie to let anyone think that i am an engineer type...hell
i am not even math literate, but i am willing to listen and learn from the
fine ceramic engineers that have helped me. i am willing to listen and learn
from nils and marc ward, cameron, ron r, buck (and don't forget that
wonderful guy in the south, space engineer, sitting on persimmon hill, and
with-
out question my dear friend feriz delkic`.
it is a pleasure and a privilege.
mel/mn
http://www.pclink.com/melpots
Potterman on fri 2 oct 98
-----Original Message-----
From: mel jacobson
To: CLAYART@LSV.UKY.EDU
Date: Wednesday, September 30, 1998 6:30 AM
Subject: firing speed
----------------------------Original message----------------------------
it is almost ironic that the person wrote and asked if 7 hours was too
fast to fire an electric kiln, with a warm up overnight.......(please do not
take this personally, or be embarrassed........we have all thought it.)
it amazes me that industry is firing pots in minutes now.........if the
water
is gone, and they are zero dry, bingo, minutes, not hours.
it is obvious that they are balancing the glaze, clay and speed of firing.
i realize that industry runs on a different standard, the engineering is
very `use` specific.......and they sure are not doing art.
but, if they can do things in minutes, why are we still soaking electric
kilns,?
pre/heating for hours?....the glazes don't care, the kiln does not care.
but, for some reason, we care. and we waste mammoth amounts of fuel.
and yet often the same people will confess to being `green`.
we are doing a great many things that was a standard in 1930.
that is what mr. cameron is speaking to, it is what mr. barrymore is
speaking to.
and i hope we listen.
it is what nils lou has been speaking to for 20 years.
big flues, too much gas, too little gas. funny stacks, arches.........and
then
crying when the
kiln will not work. and then people argue with him when he tells them
what he thinks.
dan rhodes fought for science, understanding, progress. i like to honor him
by keeping the pressure on.
it would be a great lie to let anyone think that i am an engineer
type...hell
i am not even math literate, but i am willing to listen and learn from the
fine ceramic engineers that have helped me. i am willing to listen and
learn
from nils and marc ward, cameron, ron r, buck (and don't forget that
wonderful guy in the south, space engineer, sitting on persimmon hill, and
with-
out question my dear friend feriz delkic`.
it is a pleasure and a privilege.
mel/mn
http://www.pclink.com/melpots
Mel,
My experience firing electric kilns confirms that a very fast rise in
temperature is okay once the water is gone out of the pots, but I'm more
curious to know what is the fastest time possible through the
"water-smoking" period? I'm assuming the use of a high-fired stoneware body
with at least ten percent grog, besides clay body composition (and other
obvious factors such as thickness and size) what other factors contribute?
Sincerely,
Karsten
rballou@mnsinc.com on fri 2 oct 98
Mel,
I've enjoyed reading your posts. And anyone who likes South Carolina and
shrimp, well, that strikes a chord with this ex patriate Charlestonian.
Now, as to firing speed. If I liked how industry fired ware looked, I
wouldn't need to be a potter. I could go to K Mart or Pottery Barn. Some of
it even looks okay. But it's not what I'm looking for. I like the old ways.
There are periods during a firing, both glaze and bisque, when it doesn't
matter how fast you go. But there are other points when it matters a whole
lot. My geology course was a long time ago, but I was really impressed by
the fact that what precipitates out of a volcanic lava flow depends on how
fast or slow it is cooled and at what temperature. When I look at all those
hot pots in a kiln, I imagine that I've got my own semi-tamed volcano in
there to play with. A lot of different reactions go on in a glaze and many
of them are dependent on the rate of heat rise and the rate of the cooling.
Many glazes can have crystalline development and that takes time. Any glaze
with calcium and a little magnesium, for example. These crystals will
change the appearance. Silkier surfaces, sometimes surprising color
developments. Any glaze with iron and calcium is going to be affected by
firing and cooling speed. Why not try it and see what happens? Spend a
couple of hours between ^8 and 10 on the way up and on the way down.
Just sign me.....
Ruth Ballou, Neo Luddite
Silver Spring, MD
Fraser on sat 3 oct 98
Just wanted to add my voice to the thread about firng times and why we
'should' fire slowly. I built a small fiber kiln for Raku and decided to
try firing to cone 6 - just for the hell of it. Since then I've been firing
to between cone 7 and 8 - for about 1 1/2 years now. I have developed new
glazes and can achieve almost any level of reduction. The average firing
takes about 2 1/2 hours. When I tell people about this they are usually
surprised, and in some cases, wonder why I would want to fire so quickly.
It is interesting that in the arts, populated by so many 'creative' people,
the idea of firing in a non-traditional way is looked upon with any
skepticism. I don't think of 2 to 3 hours as fast. I watch/attend all my
firing and am learning a lot about reduction and the dynamics of my kiln.
By the time I roll the kiln back in the shed I am tired. The fact is I am
not a production potter and I don't think I want to become a production
potter. I wanted a small kiln so that I could fire a few items at a time
and test lots of glazes - I can fire about 60 mugs per load. I could have
reduced the gas pressure and prolonged the firing to 12 or 14 or 16 hours,
but why? I have learned that commercial clays can withstand VERY fast
temperature increases -through quartz inversions- without compromising
structural integrity. (Just don't cool too quickly through the inversion
points. )
In the next year I want to fire a test pot with acetylene and oxygen. Why?
Because I'm curious about how the excessive carbon would affect glazes and
clay, and how fast I could drop a cone. Perhaps this method will achieve
cone 7 in 5 minutes, and still create copper reds or Shinos.
Maybe then I will have to seriously question spending an eternity firing my
old (2 hour) method.
Fraser Forsythe
fraserf@golden.net
www.golden.net/~fraserf
Canada
Roger Korn on sun 4 oct 98
Fraser Forsythe wrote:
----------------------------Original message----------------------------
Just wanted to add my voice to the thread about firng times and why we
'should' fire slowly. I built a small fiber kiln for Raku and decided to
try firing to cone 6 - just for the hell of it. Since then I've been firing
to between cone 7 and 8 - for about 1 1/2 years now. I have developed new
glazes and can achieve almost any level of reduction. The average firing
takes about 2 1/2 hours. When I tell people about this they are usually
surprised, and in some cases, wonder why I would want to fire so quickly.
It is interesting that in the arts, populated by so many 'creative' people,
the idea of firing in a non-traditional way is looked upon with any
skepticism. I don't think of 2 to 3 hours as fast. I watch/attend all my
firing and am learning a lot about reduction and the dynamics of my kiln.
By the time I roll the kiln back in the shed I am tired. The fact is I am
not a production potter and I don't think I want to become a production
potter. I wanted a small kiln so that I could fire a few items at a time
and test lots of glazes - I can fire about 60 mugs per load. I could have
reduced the gas pressure and prolonged the firing to 12 or 14 or 16 hours,
but why? I have learned that commercial clays can withstand VERY fast
temperature increases -through quartz inversions- without compromising
structural integrity. (Just don't cool too quickly through the inversion
points. )
In the next year I want to fire a test pot with acetylene and oxygen. Why?
Because I'm curious about how the excessive carbon would affect glazes and
clay, and how fast I could drop a cone. Perhaps this method will achieve
cone 7 in 5 minutes, and still create copper reds or Shinos.
Maybe then I will have to seriously question spending an eternity firing my
old (2 hour) method.
Fraser Forsythe
fraserf@golden.net
www.golden.net/~fraserf
Canada
I think that once the chemically-bound water is driven off, the only limit is
probably the thermal expansion stress caused by the thickness of the piece: the
outside warming more quickly than the inside. Cooling must be controlled through
quartz inversion/ chrystobalite formation temperature points, and various chemic
processes in glaze transformation are no doubt time-dependent, as various redox
reactions are notorious for having a time-table all their own.
Please keep us posted, and good luck! This is worth pursuing.
Roger
McKay Creek Ceramics
Michael Wendt on sat 13 jul 02
New Potters ,
You want to know... am I firing too fast or too slowly? The answer lies
with you and your process. You have to run some loads. OH MY GOD! they blew
up. That must be too fast! Keep notes and learn to make the process work for
you.
The clay used, the kiln used, the way you form your work, the degree of
dryness upon loading, how you load your stack, how fast you fire and when
you increase the rate of fire and when you slow down, how much air you let
in to burn out organics all affect the results and are unique to you.
We as a group cannot give you a definitive answer for your situation. To
get your answer requires lots of firing cycles with your process and
materials so the answer really is: experience and observation. Having said
that, we can tell you how we do things and how they work for us in our
setting.
Example: Brad Sondahl asked about the pot circles he sometimes finds in the
glaze fired pieces. No one answered on list, but I have seen them too on
occasion. After I studied the problem for a while, I noticed the circular
cracks were at a certain height, the height of the peep hole plugs in our
electric kiln which we use for bisque and which is power vented. Under
suction, when the peep hole plugs are slightly loose, cold air leaks in and
causes a microscopic hairline circular crack if a piece is very near the
peep hole which only shows in the glaze firing. We totally eliminated the
cracks by placing shields in front of the peeps. Sometimes you need to be a
forensic detective to get at the source of a problem.
If you are just starting, you are embarking on a learning experience unique
to you. Don't be shy about asking questions, but know too that our answers
may not be your answers.
Regards,
Michael Wendt wendtpot@lewiston.com
Wendt Pottery
2729 Clearwater Avenue
Lewiston, Idaho 83501
1-208-746-3724
wendtpottery.com
mel jacobson on sat 17 may 03
there are many factors to take into account.
it is not an easy call.
craig is totally correct, and his sense of this
is very good.
i have some big issues with the nurse maid approach.
it does not make sense to just ease a big gas kiln into
its firing. get after it. most kilns have a time span built
into them, or, just how long it takes to get to cone 10-11.
a great deal depends on how you bisque fire. if you follow
ron roy's schedule, take your time, get all the crap out, one
can get into the glaze firing a bit faster.
as for my firing schedule, nils and others have rather beaten
me up for going too slow. so, i just turn the burners to high
to get some energy into the kiln. as i get towards cone 5, i
turn it down. slow things down a bit.
but, no matter what i do, most times my kiln fires in 10 hours.
it always has. too much power at the end can slow
things a great deal. typical problem...always get it with
folks...`hey mel, my kiln stall at cone 8....`
i say, `turn down the gas, get it in balance`.
of course, they rarely believe me, just turn up the gas and
make the problem worse. so, why did you call?
i am greatly concerned with how i cool my kiln, and what i do
after i turn it off. i like to clear the carbon out at the end,
and fast cool for about 15 minutes...wide open.
i turn the kiln back on with one burner, oxidized when i reach
1900F. (hank murrow) let it soak for two, three hours.
then slow cool until it reaches 400F and slowly open it.
since doing this firing method, my loss ratio has gone to almost zero.
if you can get your kiln it balance, the time it takes to fire should
be left to the kiln. what you do with reduction, how much, gas
pressure, flu size will determine when the kiln is done.
perfect balance, medium reduction, nice rise in temp all the way,
will make for a great firing. wether it is 7 hours or 17....it is your
gas that goes through the meter. i don't like that meter spinning
for 7 extra hours.
mel
feriz says that in the industry, glaze firings can be 30 minutes.
but, remember that is well engineered clay and glaze. totally dry.
zero moisture. perfect balance.
From:
Minnetonka, Minnesota, U.S.A.
web site: my.pclink.com/~melpots
or try: http://www.pclink.com/melpots
new/ http://www.TICK-ATTACK.COM
| |
|
