Ivor on thu 12 feb 04
I've fired my small electric kiln successfully scores and scores of
times (and more scores), but I hanker after those reduction effects -
tenmoku, celadon, sang du boeuf (copper red). My location
means that I would have to use bottled gas and here in the UK the
choice of kiln is limited. Its a step into the unknown (for me) and a
big investment. I'm anxious.
The kiln I favour is the gas equivalent of many of those popular
electric top loaders. It's a lightweight modern design using sheet
metal and five different high-tech insulating layers. It's a front
loader.
It boasts high efficiency. Certainly, my calculations suggest that it
is claiming lower energy consumption than my similar sized
electric. (3inch wall). It is possible that a gas kiln could fire much
faster than an electric and thus save energy. But, with gas a lot of
the potential energy goes up the flue and reduction uses gas
inefficiently
The kiln is a 4 cu.ft LASER and claims 4.5kg/2.5l. of liquid
PROPANE per Cone 9 reduction firing. That's 10lb/5.5Pints (US).
Whilst the precise value is not important I'm anxious to know if
these are reasonable approximations.
So how much propane is used in a typical Cone 9 reduction with a
small (4 cu.ft) kiln?
The guy at LASER is very frank and helpful and I'm inclined to trust
him. His kilns seem to be very well specified with auto-ignition and
flame-failure protection as standard and they have a good range of
controllers and flues available.
The recommended flue (5inch) uses a rubber gaiter to get through
the kiln shed roof. Has any Clayarter experience of this type of
roof vent? The flexible vent takes the flue through a corrugated
metal roof. But the gases enter the bottom of the stack at
350degrees C (660F). Will the seal hold up? I don't want rainwater
down the outside of the flue onto the kiln itself (hot or cold).
I rely heavily on my controller for electric firings, but of course keep
it under almost constant observation. The gas controller offers
similar facilities.
But how reliable are they for gas?
I mean - how well will they control ramps and soaks?
Many of my oxidised glazes rely on careful control of soaks at top
temperature and cooling ramps. With electric the controller is
much more accurate than me twiddling the knobs. Will it be the
same with gas?
I believe there is a lot of skill in stoneware, both oxidising and
reduction. But I'm also a great believer in letting technology make
it easier. Will gas give me headaches?
Ivor
Ivor J Townshend
Macclesfield UK
william schran on fri 13 feb 04
Ivor wrote:> Will gas give me headaches?<
There are several threads on issues dealing with the sectional
updraft fuel fired kilns in the archives and I'm certain others will
also respond. I think the real question involves: why are you wanting
a gas kiln? Answer: to get reduction effects.
Have no idea how or how well a programmable controller would work on
a gas kiln. From discussions on the forum, it seems the best advice
is a pyrometer system that has thermocouples at top and bottom of the
kiln. Given the dynamics of a updraft kiln one would expect more
variations in temperature from top to bottom that one would have to
manage - more than in an electric kiln.
Bill
John Rodgers on fri 13 feb 04
Ivor,
I have fired a lot ot electric kilns without controller, many will
computer control, and fairly large - 100 cu.ft - minnisota flat-top car
kilns with semi-automatic contol and manual control. Drawing from that
experience, might I suggest that you look into purchasing new - or
modify your existing electric - kiln into the combination kiln that uses
both electricity and gas. It's a good way to go unless you really have
need of a bigger gas kiln. By going the gas/electric route, you can have
the best of both worlds. Propane is used for the gas and it's principle
function is to get the reduction more than produce heat. There have been
a number of articles written about this in the last couple of years in
the various clay magazines. PMI had a good article a couple of years ago
with our own Mel Jacobson doing the show and tell.
Regards,
John Rodgers
Chelsea, AL
Ivor wrote:
>I've fired my small electric kiln successfully scores and scores of
>times (and more scores), but I hanker after those reduction effects -
> tenmoku, celadon, sang du boeuf (copper red). My location
>means that I would have to use bottled gas and here in the UK the
>choice of kiln is limited. Its a step into the unknown (for me) and a
>big investment. I'm anxious.
>
>The kiln I favour is the gas equivalent of many of those popular
>electric top loaders. It's a lightweight modern design using sheet
>metal and five different high-tech insulating layers. It's a front
>loader.
>
>It boasts high efficiency. Certainly, my calculations suggest that it
>is claiming lower energy consumption than my similar sized
>electric. (3inch wall). It is possible that a gas kiln could fire much
>faster than an electric and thus save energy. But, with gas a lot of
>the potential energy goes up the flue and reduction uses gas
>inefficiently
>
>The kiln is a 4 cu.ft LASER and claims 4.5kg/2.5l. of liquid
>PROPANE per Cone 9 reduction firing. That's 10lb/5.5Pints (US).
>Whilst the precise value is not important I'm anxious to know if
>these are reasonable approximations.
>
>So how much propane is used in a typical Cone 9 reduction with a
>small (4 cu.ft) kiln?
>
>The guy at LASER is very frank and helpful and I'm inclined to trust
>him. His kilns seem to be very well specified with auto-ignition and
>flame-failure protection as standard and they have a good range of
>controllers and flues available.
>
>The recommended flue (5inch) uses a rubber gaiter to get through
>the kiln shed roof. Has any Clayarter experience of this type of
>roof vent? The flexible vent takes the flue through a corrugated
>metal roof. But the gases enter the bottom of the stack at
>350degrees C (660F). Will the seal hold up? I don't want rainwater
>down the outside of the flue onto the kiln itself (hot or cold).
>
>I rely heavily on my controller for electric firings, but of course keep
>it under almost constant observation. The gas controller offers
>similar facilities.
>
>But how reliable are they for gas?
>
>I mean - how well will they control ramps and soaks?
>
>Many of my oxidised glazes rely on careful control of soaks at top
>temperature and cooling ramps. With electric the controller is
>much more accurate than me twiddling the knobs. Will it be the
>same with gas?
>
>I believe there is a lot of skill in stoneware, both oxidising and
>reduction. But I'm also a great believer in letting technology make
>it easier. Will gas give me headaches?
>
>Ivor
>
>
>Ivor J Townshend
>Macclesfield UK
>
>______________________________________________________________________________
>Send postings to clayart@lsv.ceramics.org
>
>You may look at the archives for the list or change your subscription
>settings from http://www.ceramics.org/clayart/
>
>Moderator of the list is Mel Jacobson who may be reached at melpots@pclink.com.
>
>
>
wayneinkeywest on fri 13 feb 04
If I can butt in for a minute...
Yes, wood and gas fired kilns are great, and if you have the space
and the inclination, and
a source for the fuel, I'd say go for it.
However, if you are just looking for the reduction effects, you can
easily convert an electric (_any_ electric!) to a gas/electric
combination. The Mayor showed me how, and it's simpler than you can
imagine. If you want flyash effects on the other hand, you will
need a wood kiln. I haven't yet figured out how to do that in a
saggar :>)
Wayne Seidl
> Ivor wrote:> Will gas give me headaches?<
>
> There are several threads on issues dealing with the sectional
> updraft fuel fired kilns in the archives and I'm certain others
will
> also respond. I think the real question involves: why are you
wanting
> a gas kiln? Answer: to get reduction effects.
>
> Have no idea how or how well a programmable controller would work
on
> a gas kiln. From discussions on the forum, it seems the best
advice
> is a pyrometer system that has thermocouples at top and bottom of
the
> kiln. Given the dynamics of a updraft kiln one would expect more
> variations in temperature from top to bottom that one would have
to
> manage - more than in an electric kiln.
> Bill
>
Hank Murrow on fri 13 feb 04
On Feb 13, 2004, at 5:39 AM, william schran wrote:
> Have no idea how or how well a programmable controller would work on
> a gas kiln. From discussions on the forum, it seems the best advice
> is a pyrometer system that has thermocouples at top and bottom of the
> kiln. Given the dynamics of a updraft kiln one would expect more
> variations in temperature from top to bottom that one would have to
> manage - more than in an electric kiln.
Actually William;
I have not experienced any complicating problems with my Doorless
Fiberkiln that could be blamed on updraft design. The real problem in
controlling gas kilns is the atmospheric control. It is easy to arrange
a control of the gas valve to moderate temperature, but more difficult
to control atmosphere. As you know, if the gas is increased to bring
temperature up, the kiln will go into more reduction, thereby slowing
it down. So to control a gas kiln, one would need a system which opens
the damper a bit as the gas is increased so that the desired atmosphere
is maintained. And conversely, the damper should close a bit to
maintain the desired atmosphere when the gas is reduced.
The key detail is an electrical signal for atmosphere, which was
unavailable until the advent of the Oxyprobe. Someday, an entrepreneur
will combine the temp signals of the probe with the atmosphere signals
from same to moderate both gas and damper to control both quantities.
Until then, I take a look at the flame out the top every time I look at
the temperature.
BTW, my updraft kiln fires within a half cone from top to
bottom........ and the same way every time.
Cheers, Hank
http://www.murrow.biz/hank/kiln-and-tools.htm
Vince Pitelka on fri 13 feb 04
Propane is rarely cheaper than electric. Natural gas, properly applied, is
usually cheaper than electric, although prices are shifting. When it comes
to the best reduction firing effects, I have never seen a combo gas-electric
kiln that works nearly as well as a straight gas kiln (propane or natural
gas). You need that atmospheric control throughout the firing. A downdraft
gas kiln gives you the damper control needed for proper reduction firing.
Nothing else really serves the purpose.
Best wishes -
- Vince
Vince Pitelka
Appalachian Center for Craft
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Home - vpitelka@dtccom.net
615/597-5376
Office - wpitelka@tntech.edu
615/597-6801 x111, FAX 615/597-6803
http://iweb.tntech.edu/wpitelka/
http://www.tntech.edu/craftcenter/
Kathy McDonald on sat 14 feb 04
I have a DDE (?) limit controller on my kiln.
The kiln is a Geil kiln,natural gas , and it fires very economically,
however, here in Canada I think it is still cheaper for me to fire
the electric kilns. This is due to the erratic spikes in the cost
of natural gas. Electricity has stayed relatively stable.
Kathy
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG]On Behalf Of Hank Murrow
Sent: Friday, February 13, 2004 10:17 AM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: Is gas cheaper than electric?
On Feb 13, 2004, at 5:39 AM, william schran wrote:
> Have no idea how or how well a programmable controller would work on
> a gas kiln. From discussions on the forum, it seems the best advice
> is a pyrometer system that has thermocouples at top and bottom of the
> kiln. Given the dynamics of a updraft kiln one would expect more
> variations in temperature from top to bottom that one would have to
> manage - more than in an electric kiln.
Actually William;
I have not experienced any complicating problems with my Doorless
Fiberkiln that could be blamed on updraft design. The real problem in
controlling gas kilns is the atmospheric control. It is easy to arrange
a control of the gas valve to moderate temperature, but more difficult
to control atmosphere. As you know, if the gas is increased to bring
temperature up, the kiln will go into more reduction, thereby slowing
it down. So to control a gas kiln, one would need a system which opens
the damper a bit as the gas is increased so that the desired atmosphere
is maintained. And conversely, the damper should close a bit to
maintain the desired atmosphere when the gas is reduced.
The key detail is an electrical signal for atmosphere, which was
unavailable until the advent of the Oxyprobe. Someday, an entrepreneur
will combine the temp signals of the probe with the atmosphere signals
from same to moderate both gas and damper to control both quantities.
Until then, I take a look at the flame out the top every time I look at
the temperature.
BTW, my updraft kiln fires within a half cone from top to
bottom........ and the same way every time.
Cheers, Hank
http://www.murrow.biz/hank/kiln-and-tools.htm
____________________________________________________________________________
__
Send postings to clayart@lsv.ceramics.org
You may look at the archives for the list or change your subscription
settings from http://www.ceramics.org/clayart/
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melpots@pclink.com.
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Ivor on sun 15 feb 04
The kiln I was looking at was a LASER G4. Has anyone
experience of this kiln
The automatic controls are described as two part.
1) Automatic Power Pack: The burner safety controls for lighting
and flame protection all fitted to the kiln stand.
2) Automatic Controller: The electronic device that is used to
control the burners. This is programmable and normally fitted to
the wall and wired to the Power Pack.
Reduction is provided by reducing the secondary air - usually by
using the flue damper.
With the kiln on auto for temperature rise and using the damper for
reduction, life could get interesting. As Hank Murrow says these
two operations work against each other.
Has any Clayarter experience of using this kiln on automatic in
reduction? How does it perform?
Unfortunately, an inspection of the kiln would give me a round trip
of 350 miles on country roads. Before I go, I would like to find out
more about the kiln.
I'm sure gas and electric prices vary a bit from country to country.
Does anyone have quantities that can be compared. I mean for
similar sized gas and electric kilns. lbs/kg of propane versus
kilowatt-hours of electricity?
Reading between the lines of what has been written on gas, I get
the impression that results are more variable than with electric -
variation within the kiln from top to bottom, and variations between
firings. How much of this can be controlled with more attention to
detail? The way the kiln is packed and the way it is fired.
Ivor
Ivor J Townshend
Macclesfield UK
John Rodgers on mon 16 feb 04
Ivor,
It is my understanding that now there is available an ITC related
product that is used to "Treat" or coat the new elements before they are
installed in the gas/electric combo kiln. This coating elimnates the
neceed to periodically fire the elements in oxidation to remove oxides.
Once this treament or coating is applied to the elements, and the
interior of the kiln is sprayed with ITC, including the elements,
element troubles are elimnated, and there should be a long life for the
elements.
Contact Axner Pottery Supply in Oviedo, Florida for more details. They
handle all the ITC products.
Regards,
John Rodgers
Chelsea, AL
Ivor wrote:
>On 13 Feb 04, at 8:22, Jeremy McLeod wrote:
>"Do a Google" on with the keywords, gas/electric clayart. That
>should get you to threads discussing Mel Jacobson's way
>of hybridizing a small electric kiln (say 7 or 8 cu.ft.), firing it part
>way with electricity, and then introducing gas
>
>Hi Jeremy
>
>Thanks for the helpful advice. Wayne and John Rodgers sent
>similar ideas. This gas business leads to some tough decisions.
>
>Gas/electric is not entirely without a downside.
>
>Nils Lou in "The Art of Firing" states that the elements of a combo-
>kiln only last for about ten firings (or twenty - but then you have to
>fire oxidation several times between each reduction firing). A set of
>elements here costs over GBP60 (USD100). Not something you
>want to be buying at all frequently.
>
>and Vince says that only a gas kiln with damper can really do the
>business. I guess its a balancing act. You get what you pay for.
>
>Ivor
>
>
>Ivor J Townshend
>Macclesfield UK
>
>______________________________________________________________________________
>Send postings to clayart@lsv.ceramics.org
>
>You may look at the archives for the list or change your subscription
>settings from http://www.ceramics.org/clayart/
>
>Moderator of the list is Mel Jacobson who may be reached at melpots@pclink.com.
>
>
>
Ivor on mon 16 feb 04
On 13 Feb 04, at 8:22, Jeremy McLeod wrote:
"Do a Google" on with the keywords, gas/electric clayart. That
should get you to threads discussing Mel Jacobson's way
of hybridizing a small electric kiln (say 7 or 8 cu.ft.), firing it part
way with electricity, and then introducing gas
Hi Jeremy
Thanks for the helpful advice. Wayne and John Rodgers sent
similar ideas. This gas business leads to some tough decisions.
Gas/electric is not entirely without a downside.
Nils Lou in "The Art of Firing" states that the elements of a combo-
kiln only last for about ten firings (or twenty - but then you have to
fire oxidation several times between each reduction firing). A set of
elements here costs over GBP60 (USD100). Not something you
want to be buying at all frequently.
and Vince says that only a gas kiln with damper can really do the
business. I guess its a balancing act. You get what you pay for.
Ivor
Ivor J Townshend
Macclesfield UK
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