William & Susan Schran User on tue 12 jul 05
On 7/12/05 1:17 PM, "Joanne Fuller" wrote:
> Therefore, I built a trash can kiln using afiber lining. Built the fire box
entirely out of hard brick (Could not locate a reasonable source for
> soft brick) Used a 500,000 BTU weedburner & propane for fuel. The Kin heated
> rapidly (w/i one hour) to 900 C. After that, the temp began to drop. I
noticed that my propane tank had frost on it. <
We'll need some more information about the size of the kiln, size of
openings (burner port & flue), but right off the top of my head it seems a
500,000 (sure it's not 50,000) btu seems way to much overkill and you have
the pressure set way, way too high. I certainly would expect the tank to
freeze given that much gas being drawn from it. Do you have a pressure gauge
or are you just cranking that thing up? Putting the tank in a container of
water will help to keep it from freezing as readily, but given probably a
thin layer of fiber and using hard brick, you'll still have a hard time
getting decent temperatures out of it.
Post back with more specifics.
--
William "Bill" Schran
Fredericksburg, Virginia
Joanne Fuller on tue 12 jul 05
Greetings to all! I am a newbie & a huge fan of Raku. I have had several successful firing in my
electric kiln, but I would prefer to save my elements. Therefore, I built a trash can kiln using a
fiber lining. Built the fire box entirely out of hard brick (Could not locate a reasonable source for
soft brick) Used a 500,000 BTU weedburner & propane for fuel. The Kin heated rapidly (w/i one
hour) to 900 C. After that, the temp began to drop. I noticed that my propane tank had frost on
it. What am I doing wrong? Should the burner port be bigger? Or is my Flue too small. I seems
like I hit a ceiling then cannot get any hotter. Thanks for your help.
Joanne
Mike Gordon on tue 12 jul 05
Joanne,
If memory serves me, when tanks start to frost over the capacity is
getting low. Does this happen when the tank is full? MIke Gordon
On Jul 12, 2005, at 10:17 AM, Joanne Fuller wrote:
> Greetings to all! I am a newbie & a huge fan of Raku. I have had
> several successful firing in my
> electric kiln, but I would prefer to save my elements. Therefore, I
> built a trash can kiln using a
> fiber lining. Built the fire box entirely out of hard brick (Could
> not locate a reasonable source for
> soft brick) Used a 500,000 BTU weedburner & propane for fuel. The Kin
> heated rapidly (w/i one
> hour) to 900 C. After that, the temp began to drop. I noticed that
> my propane tank had frost on
> it. What am I doing wrong? Should the burner port be bigger? Or is
> my Flue too small. I seems
> like I hit a ceiling then cannot get any hotter. Thanks for your help.
> Joanne
>
> _______________________________________________________________________
> _______
> 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.
>
Tony Ferguson on tue 12 jul 05
Joanne,
Can you please send me a picture of the kiln and your burner ports and I will try to help. Any other information about your kiln and your firing would be helpful too.
Tony
Mike Gordon wrote:
Joanne,
If memory serves me, when tanks start to frost over the capacity is
getting low. Does this happen when the tank is full? MIke Gordon
On Jul 12, 2005, at 10:17 AM, Joanne Fuller wrote:
> Greetings to all! I am a newbie & a huge fan of Raku. I have had
> several successful firing in my
> electric kiln, but I would prefer to save my elements. Therefore, I
> built a trash can kiln using a
> fiber lining. Built the fire box entirely out of hard brick (Could
> not locate a reasonable source for
> soft brick) Used a 500,000 BTU weedburner & propane for fuel. The Kin
> heated rapidly (w/i one
> hour) to 900 C. After that, the temp began to drop. I noticed that
> my propane tank had frost on
> it. What am I doing wrong? Should the burner port be bigger? Or is
> my Flue too small. I seems
> like I hit a ceiling then cannot get any hotter. Thanks for your help.
> Joanne
>
> _______________________________________________________________________
> _______
> 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.
>
______________________________________________________________________________
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Tony Ferguson
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Jane Murray-Smith on tue 12 jul 05
Yes, that is true. Using a full (and even better, larger) propane bottle
will stop the freezing up.. I've been told that pouring warm water over them
will defrost them as well.. As for the firing... you should be done by an
hour. Most people I know get to 1800F in 20 minutes.(After the 1st firing,
that is; warming up the kiln and shelves takes longer the 1st time)
My propane comes off the pipe that goes into my gas kiln, so I can't say
anything useful about the BTUs you have...I'm sure someone else will.
Jane
----- Original Message -----
From: "Mike Gordon"
To:
Sent: Tuesday, July 12, 2005 11:46 AM
Subject: Re: Fiber Trash can kiln not heating to maturity
> Joanne,
> If memory serves me, when tanks start to frost over the capacity is
> getting low. Does this happen when the tank is full? MIke Gordon
> On Jul 12, 2005, at 10:17 AM, Joanne Fuller wrote:
>
>> Greetings to all! I am a newbie & a huge fan of Raku. I have had
>> several successful firing in my
>> electric kiln, but I would prefer to save my elements. Therefore, I
>> built a trash can kiln using a
>> fiber lining. Built the fire box entirely out of hard brick (Could
>> not locate a reasonable source for
>> soft brick) Used a 500,000 BTU weedburner & propane for fuel. The Kin
>> heated rapidly (w/i one
>> hour) to 900 C. After that, the temp began to drop. I noticed that
>> my propane tank had frost on
>> it. What am I doing wrong? Should the burner port be bigger? Or is
>> my Flue too small. I seems
>> like I hit a ceiling then cannot get any hotter. Thanks for your help.
>> Joanne
>>
>> _______________________________________________________________________
>> _______
>> 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.
>>
>
> ______________________________________________________________________________
> 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.
>
Gene Arnold on tue 12 jul 05
sounds like your tank is freezing up allowing the gas pressure to drop. I
had this problem in the past and would run water over the tank or set the
tank in a tub of water. then just decided to buy a 100 LB tank and not be
bothered with freeze ups.
hope this helps
Gene & Latonna
mudduck@mudduckpottery.com
www.mudduckpottery.com
----- Original Message -----
From: "Joanne Fuller"
To:
Sent: Tuesday, July 12, 2005 1:17 PM
Subject: Fiber Trash can kiln not heating to maturity
Marcia Selsor on tue 12 jul 05
> Joanne,
It take a lot of BTUs to heat up dense firebrick' I even cover my
soft brick base with fiber so I can cool the kiln down quickly when I
am doing workshops with my portable kilns.
If you are only using one tank, how big is it? I fire with a tandem
system of three tanks and two burners and I don't always use both
burners although they must be hooked up.
I think you may be using too big of a burner that is sucking the gas
out of your tank too fast causing the frost buildup.
The tip of the burner should be outside the burner port aiming into
the kiln. The flu should be about the size of the burner port. If you
have any more fiber, cover the hard bricks to save energy. You don't
say how big your burner port is. For a big bertha weed burner, I'd
use a port about 5 x 5 inches.
Good lick. Let us know what you resolve to do.
Marcia Selsor
>
>> Greetings to all! I am a newbie & a huge fan of Raku. I have had
>> several successful firing in my
>> electric kiln, but I would prefer to save my elements. Therefore, I
>> built a trash can kiln using a
>> fiber lining. Built the fire box entirely out of hard brick (Could
>> not locate a reasonable source for
>> soft brick) Used a 500,000 BTU weedburner & propane for fuel. The
>> Kin
>> heated rapidly (w/i one
>> hour) to 900 C. After that, the temp began to drop. I noticed that
>> my propane tank had frost on
>> it. What am I doing wrong? Should the burner port be bigger?
>> Or is
>> my Flue too small. I seems
>> like I hit a ceiling then cannot get any hotter. Thanks for your
>> help.
>> Joanne
Robert Briggs on wed 13 jul 05
Hi Joanne,
If you're using a 20lb propane bottle with a 500,000BTU burner and
running it for about an hour,
I can see why you are freezing up. Most raku sessions using a small
fiber kiln shouldn't last more
than 30mins to reach a ^06 maturity. Let's assume there's nothing wrong
with the 'regulator' attached
to your bottle. If the area between the gas and liquid in a propane
bottle is small, (say a 20lb bottle) a
large torch or burner, (or one thats run for an hour) will demand too
much of a conversion from liquid
to gas. When the surface area in the tank can't keep up, it freezes up.
I have used two 20lb bottles and a 'Y'
connector attached to a high pressure regulator. this gives you double
the gas transfer area and I never
had a freeze up this way. A 40lb propane bottle won't help either as the
liquid to gas area is about the
same as a 20lb bottle. As for the weed burner! For about the same price
or cheaper you can get an
MR750 propane burner from 'www.wardburner.com'. These are made for small
raku kilns.
If you want to see a small raku fiber/trashcan kiln in action you might
head over to my website and check
out my video section.
Just my 12 cents worth
Robert Briggs
www.corvusmoon.com
Marcia Selsor on wed 13 jul 05
Bill is right. You should be using a pressure gauge but I don't know
what pressure you would set for a weed burner..
I have two great burners from Marc Ward who also customized my three
tank hookup. Three little 25 pound tanks will last several days
firing two raku fiber kilns coated with ITC. I take them to
workshops. One kiln is 25" diameter and the other is about 20" d.
both are 2' high of fiber and then three layers of bricks on base
covered with fiber (not from the 50 foot roll used for kilns). I use
old kiln lids for the floors.
I keep the pressure on the regulator at 1.5 to 2.5 pounds pressure.
They are amazingly efficient. Made them both from one roll of 2"
fiber.
I also have a big raku kiln on pulleys which is 36" w. x 27" d. x
(can be adjusted in ht.) 34"ht. I use two burners on this one. -and I
go slower for my big plaques...45 minutes to temp. holding back!
A few years ago I fired over 200 pieces in my two portable kilns at a
State High School ART meet with the kids in about 2 hours. We used
shelves but were popping loads out in 10-15 minutes. People came help
to see the event and we were finished by 11 am. oops!
Marcia Selsor in Montana
>
> We'll need some more information about the size of the kiln, size of
> openings (burner port & flue), but right off the top of my head it
> seems a
> 500,000 (sure it's not 50,000) btu seems way to much overkill and
> you have
> the pressure set way, way too high. I certainly would expect the
> tank to
> freeze given that much gas being drawn from it. Do you have a
> pressure gauge
> or are you just cranking that thing up? Putting the tank in a
> container of
> water will help to keep it from freezing as readily, but given
> probably a
> thin layer of fiber and using hard brick, you'll still have a hard
> time
> getting decent temperatures out of it.
>
> Post back with more specifics.
>
>
> --
> William "Bill" Schran
> Fredericksburg, Virginia
>
Snail Scott on wed 13 jul 05
At 01:17 PM 7/12/2005 -0400, you wrote:
>...Used a 500,000 BTU weedburner & propane for fuel. The Kin heated
rapidly (w/i one
>hour) to 900 C. After that, the temp began to drop. I noticed that my
propane tank had frost on
>it...
The temperature drop was due to the pressure
drop of your propane tank cooling off - you
are drawing from it faster than it can handle.
Either don't run that big burner on full-blast,
or get another tank and join them with a manifold
so that each will only draw at half the rate.
And try to insulate those hardbricks - they're
sucking up all your heat.
-Snail
William & Susan Schran User on wed 13 jul 05
On 7/13/05 9:17 AM, "Marcia Selsor" wrote:
> I keep the pressure on the regulator at 1.5 to 2.5 pounds pressure.
We use 30# tanks, one at a time, pressure regulator set to 1.0 to 1.5
pounds, using one MR 750 burner, the Axner raku kiln (takes two people to
lift), IFB bottom, one 15" shelf on 9" posts.
First firing takes about an hour to heat up everything, after that each
firing takes 15 =AD 30 minutes depending on the load.
I've never kept track of how many firings we get out of a tank, but I do
have the tank in a large plastic container with water about 1/3 to 1/2 up
the side of the tank and never have issues with tanks freezing - we suck
every bit of gas out.
--=20
William "Bill" Schran
Fredericksburg, Virginia
Joanne Fuller on wed 13 jul 05
Success! Thanks to all who responded!
I lined my hardbrick firebox with fiber AND put my propane tank in a bucket of water.
The kiln heated much more efficiently and reached over 1000C in less than an hour!
Thanks again!
Joanne
Marcia Selsor on wed 13 jul 05
I use the 2.5 on my big kiln that also takes two to lift. I never =20
have problems with frost using my three tandem tanks until they get =20
low. Even then the frost is barely there.
Never slowed the firings down. I usually fill up my tanks after =20
serious days of firing..and they are never very low. Sometimes half =20
to three quarters empty. I use 9" posts on all three of my raku =20
kilns. I use perforated shelves that fill most of the floor in the =20
kilns. I got them from Euclid's in Canada. I had used them in Spain =20
and thought they worked great. My larger kiln takes a 20 x 28 inch =20
shelf. It takes an hour for the first firing and I go slow for my =20
plaques on the following firings , 40 minutes or so. My small kilns I =20=
ise for horse hair firings and they go really fast, 6 minutes from =20
one pot to the next batch. I fire two small pots or one large one at =20=
a time up to 1200. Pull one out and keep the pot hot with the burner =20
until I can take it out. Then I start again.I did forty pots one =20
night during an open studio. That is over twenty loads but not to =20
raku temp. It was fast though. My back was tired!!!
Marcia Selsor
On Jul 13, 2005, at 9:55 AM, William & Susan Schran User wrote:
> On 7/13/05 9:17 AM, "Marcia Selsor" wrote:
>
>
>> I keep the pressure on the regulator at 1.5 to 2.5 pounds pressure.
>>
>
> We use 30# tanks, one at a time, pressure regulator set to 1.0 to 1.5
> pounds, using one MR 750 burner, the Axner raku kiln (takes two =20
> people to
> lift), IFB bottom, one 15" shelf on 9" posts.
>
> First firing takes about an hour to heat up everything, after that =20
> each
> firing takes 15 =96 30 minutes depending on the load.
>
> I've never kept track of how many firings we get out of a tank, but =20=
> I do
> have the tank in a large plastic container with water about 1/3 to =20
> 1/2 up
> the side of the tank and never have issues with tanks freezing - we =20=
> suck
> every bit of gas out.
>
>
> --=20
> William "Bill" Schran
> Fredericksburg, Virginia
>
> ______________________________________________________________________=20=
> ________
> 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 =20
> melpots@pclink.com.
>
>
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