mel jacobson on fri 28 mar 08
want to say this again, so no one is confused.
i want to make every kiln in the world fire
with compete efficiency.
i want to stamp out 18 hour gas firings with a
20 cubic foot kiln, wasting 80 gallons of propane
and spewing out fumes for hours.
i want people to save gobs of money firing
their work.
i do not care what fuel you use. it does not matter
to me. but, if you use fuel, use it wisely, with
maximum efficiency.
the best way to make money fast in the pottery
business is cut back on your fuel bill.
and, it will be good for our world at the same time.
i do not spew platitudes. i look at the practical situation
and see how we can make things better.
if you can get your kiln to fire with veggie oil, corn cobs
or peat moss, go for it. we will stand and cheer.
i just fixed a kiln that is 18 cubic feet. flat top from
kurt and my plans.
that kiln was firing for 18 hours. the cost was nearly
300 dollars. (there was not 150 bucks worth of pots in the kiln.)
i did this:
re/made the stack to be tight. (i sat, they mortored the chimney
with clay.)
changed the flue from 91 sq inches to 30 sq inches.
took out the bag wall. (commonly called a heat dam.)
re/stacked the shelves to stagger.
turned the gas pressure to 2 lbs. from 12.
fired the kiln in 4.5 hours. 19 gallons of propane. (rough guess)
cone 10.
and these are people that would kill you because you threw
away a soda can. i fired that kiln for $44.92
and, remember, they fired the kiln the same way 23 times
before i got there. the btu's were coming in the kiln and going
right up the stack.
i asked if they even looked at my plans.
they said they had a lot of help from a guy at the jr. college
that knew kilns.
yah.
he changed all the specs.
he knew alright.
anyway.
we save fuel, time, money and then the world is a better place.
think.
then build.
then think,
then fire.
we can save a million million btu's if we do it right.
and, i do not mean 1929 technology.
and those that fire electric kilns, you can save time and
money by firing faster, with better ramps.
it can be done.
mel
from minnetonka:
website http://www.visi.com/~melpots/
clayart site:
http://www.visi.com/~melpots/clayart.html
Elizabeth Priddy on fri 28 mar 08
My wood kiln (16 cu ft) fires on all found wood.
It takes about a 1/2 cord to fire it, and I have 3 cord
in reserve from only one tree culling in a neighbor's
yard, had for the cost of moving it. The blast wood comes
from a fine cabinet shop owned by a friend that can supply me
with a truckload of hardwood 1x1's every 8 days or so, as
long as he is in business. And when he stops, there is a
moulding company a town over that offers it for free as well.
Where there is a will there is a way.
E
Elizabeth Priddy
Beaufort, NC - USA
Natural Instincts Conference Information:
http://downtothepottershouse.com/NaturalInstincts.html
http://www.elizabethpriddy.com
http://www.flickr.com/photos/7973282@N03/
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steve graber on fri 28 mar 08
it helps to mention this often, but large manufacturing plants often PAY people to take their wood pallets away.
while i hear some do not like the nails that may get into the fire stream, other like the extra flash of this or that.
so if you know there's a local LARGE manufacturing plant, cheak out their waste pile!
see ya
Steve Graber, Graber's Pottery, Inc
Claremont, California USA
The Steve Tool - for awesum texture on pots!
www.graberspottery.com steve@graberspottery.com
----- Original Message ----
From: Elizabeth Priddy
To: CLAYART@LSV.CERAMICS.ORG
Sent: Friday, March 28, 2008 2:07:04 PM
Subject: Re: ecology and kilns 2
My wood kiln (16 cu ft) fires on all found wood.
It takes about a 1/2 cord to fire it, and I have 3 cord
in reserve from only one tree culling in a neighbor's
yard, had for the cost of moving it. The blast wood comes
from a fine cabinet shop owned by a friend that can supply me
with a truckload of hardwood 1x1's every 8 days or so, as
long as he is in business. And when he stops, there is a
moulding company a town over that offers it for free as well.
Where there is a will there is a way.
E
Elizabeth Priddy
Beaufort, NC - USA
Natural Instincts Conference Information:
http://downtothepottershouse.com/NaturalInstincts.html
http://www.elizabethpriddy.com
http://www.flickr.com/photos/7973282@N03/
---------------------------------
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______________________________________________________________________________
Clayart members may send postings to: clayart@lsv.ceramics.org
You may look at the archives for the list, post messages, change your
subscription settings or unsubscribe/leave the list here: http://www.acers.org/cic/clayart/
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Nancy Guido on sat 29 mar 08
"it helps to mention this often, but large manufacturing plants often PAY people
to take their wood pallets away."
This statement is true, however, my hubby says you need to be prepared to take ALL the pallets which may mean you will need a truck, maybe even a semi.
nancy g.
Ivor and Olive Lewis on sat 29 mar 08
Dear Friends,=20
As I see it, (and I have been building kilns as long as, if not longer =
than most who contribute to Clayart) a kiln should be fired as fast as =
possible consistent with meeting those concepts that prevent destroying =
the work you have made.
The danger periods are when you have to eliminate free water which will =
evaporate and blow your work into fragments, say 80-120 deg C (170- 250 =
F), then during Kaolin de-hydroxylisation , 450-550 deg C (840-1020 F) =
and running through the Quartz Phase change slowly between 500 and 600 =
deg C (930-1120 F) if your clay contains significant volumes of free =
silica.
Small kilns, say up to sixty cubic feet with insulating refractories =
should be able to achieve a temperature rise well above 100 deg C per =
hour (212 F) provided they are not underpowered
Note that the maximum temperature rise recommended for Orton Cones is =
about 120 deg C/hr (248F/hr) so a studio kiln should fire to cone 8 in =
eleven hours, cone 6 in ten hours.
If you can afford one, get an Oxyprobe and use it to obtain maximum fuel =
efficiency.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
John Britt on sun 30 mar 08
Ivor,
As far as I rmember, the temperature rise that Orton recommends is only
for the last 90 - 120 minutes of the firing or 100 -200 F. So there is no
relationship with what Orton recommends for accurate cone melting and how
fast kilns should be fired before that time.
You can fire kilns very fast with good results and without destroying the
work. I fire mine in about 5 hours and get great copper reds, shinos and
celadons. I talked to Jon Singer at NCECA who told me he has a test kiln
that he fires in 1 hour! But, I also know that you get some great results
with week long firings.
John Britt
Rick Hamelin on sun 30 mar 08
Hello all,
These comments reminded me of an old potter's diary from the late 1700's that I read some years back. His wood fired kiln suddenly demanded more wood to heat and cooled so quickly that the wares were cracking. He was forced to dismantle the kiln after several lost loads and found that rats had tunnelled under the kiln pad, effectively creating flues right into the kiln.
I had, sometime ago, queried everyone about wrapping my electric kilns with
kaowool and completed this part of my updates about two months ago. Thank you again.
I wrapped one inch of the safer fiberwool over the stainless steel jacket and secured
it with overlapping 12 inch aluminum flashing held down with self-drilling metal
screws. The project was fast and easy. The kiln certainly fires more rapidly; so
much so that the infinite switches needed to be "turned down" for some wares. It
cost me just $50 a kiln to do.
My next project will be replacing those switches with relays and temperature
controllers run by the old computer.
Take care,
Rick
www.americanredware.com
--
"Many a wiser men than I hath
gone to pot." 1649
Ron Roy on mon 31 mar 08
Hi Ivor,
While I do agree that slow is mandatory till all the atmospheric water is
gone - I have direct experience that firing fast through the water smoking
stage and quartz inversion is fine.
RR
>As I see it, (and I have been building kilns as long as, if not longer
>than most who contribute to Clayart) a kiln should be fired as fast as
>possible consistent with meeting those concepts that prevent destroying
>the work you have made.
>The danger periods are when you have to eliminate free water which will
>evaporate and blow your work into fragments, say 80-120 deg C (170- 250
>F), then during Kaolin de-hydroxylisation , 450-550 deg C (840-1020 F) and
>running through the Quartz Phase change slowly between 500 and 600 deg C
>(930-1120 F) if your clay contains significant volumes of free silica.
>Small kilns, say up to sixty cubic feet with insulating refractories
>should be able to achieve a temperature rise well above 100 deg C per hour
>(212 F) provided they are not underpowered
>Note that the maximum temperature rise recommended for Orton Cones is
>about 120 deg C/hr (248F/hr) so a studio kiln should fire to cone 8 in
>eleven hours, cone 6 in ten hours.
>If you can afford one, get an Oxyprobe and use it to obtain maximum fuel
>efficiency.
>
>Best regards,
>Ivor Lewis.
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Ivor and Olive Lewis on mon 31 mar 08
No argument with your summation John.
But I believe I prefaced my piece with this remark :-
"As I see it.... a kiln should be fired as fast as possible consistent
with meeting those concepts that prevent destroying the work you have
made."
You will find in back issues of INTERCERAM articles that describe
rapid processing of porcelain ware. From memory I recall a full cycle
of ninety mins with arrested cooling through the quartz transitions.
B. Leach describes a temporary kero fired kiln which heats up to cone
8 or so in 3/4 hr. I would be guarded about using results from such
test kilns to predict outcomes from production kilns.
If a ramp up of ~550 Deg C (~1020 F) gives you the product your
customers require at the economic return you require then, that is
what you must do.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
Subject: Re: ecology and kilns 2
> Ivor,
>
> As far as I rmember, the temperature rise that Orton recommends is
only
> for the last 90 - 120 minutes of the firing or 100 -200 F. So there
is no
> relationship with what Orton recommends for accurate cone melting
and how
> fast kilns should be fired before that time.
>
> You can fire kilns very fast with good results and without
destroying the
> work. I fire mine in about 5 hours and get great copper reds, shinos
and
> celadons. I talked to Jon Singer at NCECA who told me he has a test
kiln
> that he fires in 1 hour! But, I also know that you get some great
results
> with week long firings.
>
>
> John Britt
Arnold Howard on mon 31 mar 08
From: "steve graber"
> it helps to mention this often, but large manufacturing
> plants often PAY people to take their wood pallets away.
>
You could also call fence companies and offer to haul away
wood for them. I built a new fence two summers ago and had
huge stacks of wood from the old fence that I replaced.
Sincerely,
Arnold Howard
Paragon Industries, L.P., Mesquite, Texas USA
ahoward@paragonweb.com / www.paragonweb.com
Ivor and Olive Lewis on tue 1 apr 08
<
While I do agree that slow is mandatory till all the atmospheric water =
is gone - I have direct experience that firing fast through the water =
smoking stage and quartz inversion is fine.>>
Dunting during heating is not unknown Ron.
And as I said, a lot will depend upon the mineral analysis of a clay =
body. I would consider that bodies with high fractions of coarse silica =
grog be treated with care and attention during heating and cooling.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
Ron Roy on tue 1 apr 08
Hi Ivor,
I assume we are still talking about bisque firing - I would agree that fast
heating can lead to dunting when refiring glazed ware.
As I said - I have not seen it - fired a bisque load up to 600C in an hour
once (after it was dry) - reprogrammed the controller for the rest of the
firing and all was fine when I opened the kiln.
Remember - on the way down the quartz inversion makes the rim get smaller
before the rest of the bowl if the cooling is too fast. That can easily
lead to dunting.
On the way up the rim gets bigger when the quartz goes from alpha to beta -
not as likely to crack a pot.
In a bisque firing - how do you know if the dunting happened on the way up
or on the way down?
RR
><>
>While I do agree that slow is mandatory till all the atmospheric water is
>gone - I have direct experience that firing fast through the water smoking
>stage and quartz inversion is fine.>>
>
>Dunting during heating is not unknown Ron.
>
>And as I said, a lot will depend upon the mineral analysis of a clay
>body. I would consider that bodies with high fractions of coarse silica
>grog be treated with care and attention during heating and cooling.
>
>Best regards,
>
>Ivor Lewis.
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
joyce on tue 1 apr 08
Thank you for all the private posts you sent explaining to me
again what atmospheric and chemical waters are, and how to
fire them. I now have one more question since I seem to not
be making this particular connection.
Okay.......... slow through the atmospheric water stage....... slow
or fast through the chemical water (smoking water)/quartz inversion stage,
according to what
works for you and your kiln. NOW........ I can work with that with
somewhat of a clearer head........... BUT:
Does the quartz inversion
occur again during the glaze firing? The answer may be obvious to
most, but not to me. I mean, you're going through the 450 degree
(?) fire again, right? So, does the inversion occur everytime you
pass through.................and is 450 correct? Some of my firings are
more uneven
than others and I'm wondering if I'm going too fast through the
quartz inversion fire?
Thank you....... and please forgive my awkward phrasing. It's the
best I can do until I get it worked out ........ most issues I can
kind of "work through" myself, but this one has me a bit stuck.....
probably because I forget about it until somebody brings it up
again ...........
Joyce
In the Mojave desert of California U.S.A.........
Michael Wendt on tue 1 apr 08
My theory about how to tell when something
cracked in bisque on the way up or down:
If heated too fast, the edge closest to the elements
expands faster than the edge farthest from
the heat source. Clay is stronger in compression
than tension so the cool side cracks.
Likewise, if cooled too quickly, the outer edge
is now in tension and the crack is there.
Ron Roy wrote:
"On the way up the rim gets bigger when the quartz goes
from alpha to beta -
not as likely to crack a pot.
In a bisque firing - how do you know if the dunting
happened on the way up
or on the way down?
RR"
Regards,
Michael Wendt
Wendt Pottery
2729 Clearwater Ave.
Lewiston, Id 83501
U.S.A.
208-746-3724
wendtpot@lewiston.com
http://www.wendtpottery.com
http://UniquePorcelainDesigns.com
Snail Scott on wed 2 apr 08
> Date: Tue, 1 Apr 2008 09:44:09 -0700
> From: joyce
>
> ...Some of my firings are
> more uneven
> than others and I'm wondering if I'm going too fast through the
> quartz inversion fire?
Did stuff crack at the thin parts, or at joints between
thick and thin? If not, then no problem. Frankly, I've
never met an electric kiln capable of going too fast
through quartz inversion, even if you tried.
-Snail
Ron Roy on fri 4 apr 08
I think it's a good question Joyce - we should all have it clear in our
heads - it is so important when trying to figure out dunting and glaze fit
problems.
If there is any free quartz in a clay body - I have never found none by the
way - it shows up clearly on a dilatometer chart - it goes through a volume
change at 573C - 1063F.
When heating the quartz goes from alpha to beta with an increase in size of
about 2% at 573C - only alpha quartz can exist below 573C and only beta
above that. The expansion and contraction is exactly the same each time -
in other words - exactly reversible.
The change is greater in bisque because hardly any of the quartz has
entered into the melt - there will be less free quartz in the same clay
fired higher. Thats a good reason to fire bisque to 04 because more of the
quartz is taken into the melt and the ware is stronger - meaning it can
better resist the stresses when the quartz in the rim of a bowl goes
through the inversion (from Beta to Alpha) during cooling - before the rest
of the bowl. Rim suddenly get smaller - foot being thicker and in contact
with a hot kiln shelf - does not get smaller.
You can tell if the crack happened on the way up - the crack will be a
little open because some melting has taken place. If the crack happened on
the way down it will be tight - sometimes you will miss it because it has
closed up again - after the rest of the pot goes through the inversion
temperature.
Having some free quartz in a clay body after a glaze firing is a good thing
for glaze fit - as the pot gets smaller at 573C it helps keep a non crazed
glaze in compression - very helpful in controlling crazing. Thats why one
of the cures for crazing is adding more silica to the clay body.
Cristobalite - another form of silica - does the same thing at around 200C.
The problem with that is it will happen in the oven and that is not good.
Not good either if your glaze already has a lower than usual expansion -
the body tries to get smaller but the glaze will not let it.
Anyone who needs to understand this better should read Hamer - there are 10
pages on silica - it is by far the more important oxide we use.
RR
>Thank you for all the private posts you sent explaining to me
>again what atmospheric and chemical waters are, and how to
>fire them. I now have one more question since I seem to not
>be making this particular connection.
>
>Okay.......... slow through the atmospheric water stage....... slow
>or fast through the chemical water (smoking water)/quartz inversion stage,
> according to what
>works for you and your kiln. NOW........ I can work with that with
>somewhat of a clearer head........... BUT:
>
> Does the quartz inversion
>occur again during the glaze firing? The answer may be obvious to
>most, but not to me. I mean, you're going through the 450 degree
>(?) fire again, right? So, does the inversion occur everytime you
>pass through.................and is 450 correct? Some of my firings are
> more uneven
>than others and I'm wondering if I'm going too fast through the
>quartz inversion fire?
>
>Thank you....... and please forgive my awkward phrasing. It's the
>best I can do until I get it worked out ........ most issues I can
>kind of "work through" myself, but this one has me a bit stuck.....
>probably because I forget about it until somebody brings it up
>again ...........
>
>Joyce
>In the Mojave desert of California U.S.A.........
>
>______________________________________________________________________________
>Clayart members may send postings to: clayart@lsv.ceramics.org
>
>You may look at the archives for the list, post messages, change your
>subscription settings or unsubscribe/leave the list here:
>http://www.acers.org/cic/clayart/
>
>Moderator of the list is Mel Jacobson who may be reached at melpots2@visi.com
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Ivor and Olive Lewis on sat 5 apr 08
Dear Joyce,
You tell us
> ...Some of my firings are
> more uneven
> than others and I'm wondering if I'm going too fast through the
> quartz inversion fire?
The trick is to ensure that all parts pass through phase changes =
simultaneously. Some modern rapid industrial firings are programmed to =
arrest temperature changes during heating and cooling as product passes =
through critical temperatures. This assists in alleviating mechanical =
stress imposed by phase changes. However, for us this is difficult to =
achieve so we do not rush a firing through the critical phase change =
temperatures. If the load is uneven with very thick and very thin =
sections dominating the load, keep the rate of temperature change slow =
during the critical periods. See the diagrams in Hamer and Hamer (1st Ed =
pp 265-272) for critical temperatures.
If you are going fast enough to cause trouble you will know about it.
Best regards,
Ivor.
Ivor Lewis.
Redhill,
South Australia.
If you=20
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