Ingeborg Foco on wed 21 jun 00
Dear Ruth,
My next studio has a similar situation and I'm concerned as you about the
long range safety of the wood framed ceiling over the kiln. I've searched
the web and found a paint that I think I am going to apply to the wood. It
is a paint called "Thermo Shield" is water based, pure acrylic resin system
filled with hollow sodium borosilicate glass microspheres. Each microsphere
acts as a sealed cell and the entire mastic acts as a thermally efficient
blanket covering the structure protected."
Contact: John Ferdinando at 1 800-947-6727 www.aeccoatings.com
Company Name: Advanced Environmental Coatings
He doesn't know anything about kilns but gave me enough information to feel
that this is probably a good product for my application. I believe the wood
has to be new or raw - not previously painted.
It also has a class 1 fire rating which I'm sure will make the fire marshal
feel better too as he doesn't know anything about kilns either. A gallon of
the stuff runs somewhere around $ 25 US plus shipping.
Oh, most of the other paints I located on the web were just fire retardants
that is if you had flames shooting up, the ceiling wouldn't catch on fire.
However, you really received no long term protection from extreme heat.
Hope this helps
Ingeborg
----- Original Message -----
From: Ruth Conway
To:
Sent: Wednesday, June 21, 2000 7:31 AM
Subject: preventing a wood fired kiln shed from burning down
> I built a wood kiln a little over a year ago and am concerned about
the
> possibility of eventually burning down the shed roof. The shed has no
walls
> and is built on a slope as is the kiln. From the top of the cantanary
arch
> (which has plenty of Kaowool and stucco)to the wooden cross beams is 18"
> and from the blow hole to the support beam is 30". It is the blow hole
which
> concerns me. Does any one have suggestions of ways to protect the cross
> beams under the blow hole? Concrete board? or would that trap heat and
> prevent moisture reaching the beams? Pin holes in the roof to let rain
seep
> onto the wood beams,but doesn't the flash point of wood lower with each
> firing regardless? What have those of you who have had wood kilns for a
> long time done. Should I just except a conflagration in years to come? I
> would like to prevent it...........Ruth Conway
> ________________________________________________________________________
> Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.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.
>
Ruth Conway on wed 21 jun 00
I built a wood kiln a little over a year ago and am concerned about the
possibility of eventually burning down the shed roof. The shed has no walls
and is built on a slope as is the kiln. From the top of the cantanary arch
(which has plenty of Kaowool and stucco)to the wooden cross beams is 18"
and from the blow hole to the support beam is 30". It is the blow hole which
concerns me. Does any one have suggestions of ways to protect the cross
beams under the blow hole? Concrete board? or would that trap heat and
prevent moisture reaching the beams? Pin holes in the roof to let rain seep
onto the wood beams,but doesn't the flash point of wood lower with each
firing regardless? What have those of you who have had wood kilns for a
long time done. Should I just except a conflagration in years to come? I
would like to prevent it...........Ruth Conway
________________________________________________________________________
Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com
Earl Brunner on wed 21 jun 00
One of the design features of a Geil kiln that I noticed a
while back is that Paul has placed a second skin of sheet
metal an inch or two out from the actual outside wall of the
kiln. This dead air space is open at the top and bottom.
YOu can put your hand on the outside skin of the kiln at top
temperature whereas you probably could not do so with out
that second skin.
You might consider placing some sheet metal panels in the
areas that you are concerned about. If you do so with
spacers to hold the sheet metal out away from the wood an
inch or two then the wood could still "breath".
Ruth Conway wrote:
>
> I built a wood kiln a little over a year ago and am concerned about the
> possibility of eventually burning down the shed roof. The shed has no walls
> and is built on a slope as is the kiln. From the top of the cantanary arch
> (which has plenty of Kaowool and stucco)to the wooden cross beams is 18"
> and from the blow hole to the support beam is 30". It is the blow hole which
> concerns me. Does any one have suggestions of ways to protect the cross
> beams under the blow hole? Concrete board? or would that trap heat and
> prevent moisture reaching the beams? Pin holes in the roof to let rain seep
> onto the wood beams,but doesn't the flash point of wood lower with each
> firing regardless? What have those of you who have had wood kilns for a
> long time done. Should I just except a conflagration in years to come? I
> would like to prevent it...........Ruth Conway
> ________________________________________________________________________
> Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.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.
--
Earl Brunner
http://coyote.accessnv.com/bruec
mailto:bruec@anv.net
Dave Finkelnburg on wed 21 jun 00
Hi Ruth!
You are asking an excellent question! David Hendley has pointed out in
the past, very clearly, that the best course is to make the kiln shed
non-flammable. He likes steel buildings. It's hard to argue with the
safety of that.
For your situation, I strongly advise creating an air gap. The concrete
board is a good start, but it needs to be set out from the roof structure
about an inch or so, thereby allowing air to move between the board and the
roof support structure. Creating such an air gap, where the air can flow
freely out as it warms up, has the same effect as moving the roof structure
6 to 12-inches further from the heat source.
To make the air gap, simple fasten the concrete board, or whatever other
material you use, such as sheet metal, with metal fasteners, through some
sort of non-flammable spacer, to the roof structure.
Good for you for thinking about the situation and taking steps to
prevent a problem!
Dave Finkelnburg
-----Original Message-----
From: Ruth Conway
To: CLAYART@LSV.CERAMICS.ORG
Date: Wednesday, June 21, 2000 10:38 AM
Subject: preventing a wood fired kiln shed from burning down
> I built a wood kiln a little over a year ago and am concerned about
the
>possibility of eventually burning down the shed roof. The shed has no
walls
>and is built on a slope as is the kiln. From the top of the cantanary arch
>(which has plenty of Kaowool and stucco)to the wooden cross beams is 18"
>and from the blow hole to the support beam is 30". It is the blow hole
which
>concerns me. Does any one have suggestions of ways to protect the cross
>beams under the blow hole? Concrete board? or would that trap heat and
>prevent moisture reaching the beams? Pin holes in the roof to let rain
seep
>onto the wood beams,but doesn't the flash point of wood lower with each
>firing regardless? What have those of you who have had wood kilns for a
>long time done. Should I just except a conflagration in years to come? I
>would like to prevent it...........Ruth Conway
DONPREY@AOL.COM on thu 22 jun 00
Ruth,
On a kiln shed we have recently put into service we are using a wrapping of
Kaowool and construction grade aluminum foil around the beams.....Kaowool
next to the wood and foil on the outside. We are expecting the foil to
reflect most of the heat and dissipate the rest rather quickly by convection
cooling. The next time we fire I think I'll put a thermometer at the wood
face to see how we are actually doing.
Don Prey in Oregon
ginny bivaletz on thu 22 jun 00
my gas downdraft is also housed inside and i have the
same concerns as you. i bought cement board and
installed it with these metal spacers that they sell.
it keeps the cement board (fireboard) away from the
wall. i even drilled some 2" holes in the blocking
where the walls meet the roof and screened them so no
birds could get in. that allows cool air to come in
from outside and get under the cement board. so far
so good, but i wish mu kiln room was twice the size
and the ceiling alot higher. oh well, next lifetime.
ginny from orcas island, washington
--- Earl Brunner wrote:
> One of the design features of a Geil kiln that I
> noticed a
> while back is that Paul has placed a second skin of
> sheet
> metal an inch or two out from the actual outside
> wall of the
> kiln. This dead air space is open at the top and
> bottom.
> YOu can put your hand on the outside skin of the
> kiln at top
> temperature whereas you probably could not do so
> with out
> that second skin.
> You might consider placing some sheet metal panels
> in the
> areas that you are concerned about. If you do so
> with
> spacers to hold the sheet metal out away from the
> wood an
> inch or two then the wood could still "breath".
>
> Ruth Conway wrote:
> >
> > I built a wood kiln a little over a year ago
> and am concerned about the
> > possibility of eventually burning down the shed
> roof. The shed has no walls
> > and is built on a slope as is the kiln. From the
> top of the cantanary arch
> > (which has plenty of Kaowool and stucco)to the
> wooden cross beams is 18"
> > and from the blow hole to the support beam is 30".
> It is the blow hole which
> > concerns me. Does any one have suggestions of ways
> to protect the cross
> > beams under the blow hole? Concrete board? or
> would that trap heat and
> > prevent moisture reaching the beams? Pin holes in
> the roof to let rain seep
> > onto the wood beams,but doesn't the flash point
> of wood lower with each
> > firing regardless? What have those of you who
> have had wood kilns for a
> > long time done. Should I just except a
> conflagration in years to come? I
> > would like to prevent it...........Ruth Conway
> >
>
________________________________________________________________________
> > Get Your Private, Free E-mail from MSN Hotmail at
> http://www.hotmail.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.
>
> --
> Earl Brunner
> http://coyote.accessnv.com/bruec
> mailto:bruec@anv.net
>
>
______________________________________________________________________________
> 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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Norman van der Sluys on fri 23 jun 00
Ruth,
I would shield the wood with sheet metal applied with stand-offs of an inch or two
at least, so you have air circulation between the wood and the metal heat shield.
To shield the (metal) roof on our gas updraft kiln I constructed a device like a
table with angle iron legs and plate steel (have a friend who had some 1/2"thick
stuff around so I used that, but it's overkill.) there is about 14" between the
exit flue and the "table" top and maybe 8" between the shield and the roof. You
cannot tell by feel that that roof is directly above the exit flue. It doesn't
even warm up at the end of a 12-hour glaze firing! Hope this helps.
Norman van der Sluys
In idyllic western Michigan, where we just got a call from the gallery "did you
fire that new kilnload yet? We need more pots!" so a marathon 8-hour
glazing/kilnloading session followed and now we're waitiing for the kiln to cool.
Ruth Conway wrote:
> I built a wood kiln a little over a year ago and am concerned about the
> possibility of eventually burning down the shed roof. The shed has no walls
> and is built on a slope as is the kiln. From the top of the cantanary arch
> (which has plenty of Kaowool and stucco)to the wooden cross beams is 18"
> and from the blow hole to the support beam is 30". It is the blow hole which
> concerns me. Does any one have suggestions of ways to protect the cross
> beams under the blow hole? Concrete board? or would that trap heat and
> prevent moisture reaching the beams? Pin holes in the roof to let rain seep
> onto the wood beams,but doesn't the flash point of wood lower with each
> firing regardless? What have those of you who have had wood kilns for a
> long time done. Should I just except a conflagration in years to come? I
> would like to prevent it...........Ruth Conway
> ________________________________________________________________________
> Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.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.
John Baymore on fri 23 jun 00
On a kiln shed we have recently put into service we are using a wrapping =
of
Kaowool and construction grade aluminum foil around the beams.....Kaowool=
next to the wood and foil on the outside. We are expecting the foil to
reflect most of the heat and dissipate the rest rather quickly by
convection
cooling. The next time we fire I think I'll put a thermometer at the woo=
d
face to see how we are actually doing.
This is a possible solution....... but sometimes, depending on how it is
done, it can make the problem worse. While the insulation CAN keep heat
from getting to the wood........it can also prevent heat from dissapating=
FROM the wood. It is also important to remember that partialy pyrolized
wood (heated and super dried) starts to burn at a lower temperature than
"fresh" wood. So what appeared to work OK when the kilnshed was new.....=
might not work when the kiln has been fired a dozen or more times. The
wood of the kilnshed is ever changing. WATCH the roof penetration point
carefully for the life of the kiln. =
Best solution is to make sure that there is a open air space between a
reflective surface / insulation and the wood itself. That way the
insulation does not RETAIN heat that gets to the wood from an unexpected
source. Use some form of "standoffs" to place the insulation and
reflective surface between the wood and the chimney structure that is
radiating heat. This open air space lets the wood disapate heat to the
air. Plan this installationso that there is air FLOW across the wood
surface if you can.
While radiant heat off the brickwork is often a problem, the generation o=
f
hot air is ALSO a problem, particluarly if it is "pooling" in enclosed de=
ad
air spaces in the roof structure. Often the "pocket" that is formed by t=
he
rafter framing around the chimney forms a nice dead air pocket prime for =
a
fire.
While it is a bit complex to construct, it is good to make the flashing
design around the chimney at the roof penetration point have free airflow=
to the outside. This flow of air across the chimney surface and up and O=
UT
of the interior roof area past/through the flashing helps to prevent a
stagnant pool of superheated air from accumulating in the rafter pocket
near the chimney. This airflow also lowers the exterior surface
temperature of the chimney itself, making it a less effective radiant hea=
t
source.
This construction requires a sort of "interlocking" overlap between the
flashing on the chimney itself, and that on the roof structure. They
don't really connect to each other.... there is a passage through which a=
ir
can flow, but water/snow can't typically get into the room below.
Depending on the construction of the kiln and the type of site .......
sometimes it is good to just not flash the roof penetration point at all
and let the little water that gets in there just happen. Design the kiln=
structure to "deal" with this occasional watering. This is obviously mor=
e
appropriate for outdoor kilns under a shed roof, or primitive kilns.
Another option is to run the flue as a horizontal breech at floor level o=
ut
through a vertical wall, and then construct the chimney as a free-standin=
g
unit away from the roof structure...... eliminating the need for a roof
penetration at all. It is easier to "weatherproof", verminproof, and
fireproof the hole in the wall compared to a roof hole .
A good cooling solution for a wood kiln chimney is to utilize a passive
damper (open hole in the chimney) to cool the chimney as fast as possible=
at the end of the firing. It seems that most wood kiln roof fires start
AFTER the firing is over and the kiln is "cooling". To accomplish this y=
ou
need to have a typical slab-type damper located BELOW (downstream) of the=
passive damper. When the firing is done, you close the slab damper fully=
to seal the kiln for cooling, and fully open the passive damper(s) (let a=
ir
flow in through it). This steady flow of air into the upper part of the
chimney will rapidly cool it, helping to reduce the risk of overheated ro=
of
wood. I utilize this approach on my noborigama.
Also, when I finish a firing of my noborigama, before I go to
sleep.......... I routinely use a hose to lightly spray the interior of t=
he
roof around the chimney and the outer brick of the chimney near the roof
penetration point. This creates a lot of steam but also disapates a lot =
of
heat. This is a light spray.... not a deluge . I spray until the wo=
od
STAYS a little wet. Any water dripping onto the last chamber arch is als=
o
rapidly turned to steam since that chamber is at peak temperature right
about then. While it is a little stressful for the upper chimney
brick..... they are cheap compared to the damage that could be caused by =
a
fire. And they have taken this particular treatment for the past 20
years.....so I'm not too worried about longevity .
Good housekeeping helps prevent kilnshed fires too. I also carefully rak=
e
the entire area around the kiln, and fully hose down that and the
surrounding area. The pile of "rakings" which ususally includes a lot o=
f
little pieces of wood..... is done into a sandy clearing by itself in cas=
e
some coals happend into that pile....and it too is hosed down. Since I a=
m
usually exhausted after a firing of the kiln........ I spend a long time
making sure that the area around the kiln is as "firesafe" as possible
before I will allow myself to go to bed. I check and double-check myself=
,
since I can't really "trust" that my judgement is all that good at that
point. (A routine checklist can help in these circumstances.) =
Everything is cleaned up as best as possible, and every opening and port =
of
the kiln is closed off and checked twice. A "coal search" is performed a=
nd
every piece of supposedly "dead" wood coal that might have found it's way=
onto the ground is wet down and raked up next to the outer kiln structur=
e.
Every piece of wood that shows signs of having been heated or charred is=
segregated into the wet rakings pile. The few excess bundles of unburned=
wood used near the kiln are picked up and segregated in thir OWN pile nea=
r
the rakings pile and left uncovered by a tarp. The remaining main wood
piles are checked and tidied up. Woodpile tarps are secured with bungies=
in case of wind coming up. Any occasional errant dry leaves are also rak=
ed
away in case of wind.
As to clearance above blowholes...... it depends on the size of the
blowholes and how heavily you tend to stoke . How much flame you get
out of a blowhole determines the clearance above it. My pair of blowhole=
s
in each of the arches are round and about one inch in diameter (ducted
through round extrusions) ....and have about six or seven inches of flame=
coming out of them at the most. I've also seen blowholes on other kilns
that looked like a 200,000 BTU gas burner at full throttle with about 30
percent primary air . If you are concerned about the roof after
watching a firing of your kiln............ you probably have a right to b=
e
concerned. Woodfirers tend to be attuned to the flame. If nothing
else....it'll give you peace of mind.... and that is important too .
Use some lagbolts and bushings (pieces of iron pipe nipple will do) to
"stand off" a sheet of sheet metal about -2 inches away from the wood
surface above the blow hole area. This also helps with sparks getting up=
there . Other options would be any sheets of fireproof material like
the popular boards used near woodstoves. You can also add fireproof
insulation behind this surface as long as there is still clearance for
airflow BEHIND the insulation and over the exposed wood. Ceramic fiber i=
s
NOT necessary here ...... the grade of heat is not that high. Ceramic
block insulation is just fine and a little less hazardous in the dust
department....and cheaper too. Even unbacked fiberglass insulation is OK=
in this application.
I think the biggest fire danger with any kiln is assumptions . A
variation on that old saying tends to apply .............. "Familarity
breeds ......... fires." Potters tend to get complacent with fire. We
work with fire as a friend and collaborator. There is a whole other side=
to fire. Go downtown and ask any fireman you find at the local
firestation. They see fire from the other perspective........... fire a=
s
opponent and foe. They are right too. There is a balance in the
middle....... the Aretha Franklin factor..........called "respect" . =
I've been woodfiring since 1968....and I still think a LOT about "fire" a=
nd
it's behavior every time I build a kiln or fire a kiln. Fire can bless
us......... but it also can kill us . Never get complacent around fir=
e.
It'll test ya', and as most potters know from trying to fire pots......
when fire wants to be ornery........ it can be a difficult beast . =
Hope a thought or two here is helpful to someone.
Best,
........................john
John Baymore
River Bend Pottery
22 Riverbend Way
Wilton, NH 03086 USA
603-654-2752 (s)
800-900-1110 (s)
JBaymore@compuserve.com
John.Baymore@GSD-CO.com
"Earth, Water, and Fire Noborigama Woodfiring Workshop August 18-27,
2000"
David Hendley on fri 23 jun 00
As Dave Finkelnburg pointed out, stamping out wood framed
kiln sheds is one of my crusades. (Yes, I learned the hard way).
It's hard to say for sure without seeing what you have, but
maybe you could replace the wooden beams that are close to
the kiln with steel beams. Just bolt them on to the framework.
The next best thing would be, as others have mentioned,
to create an air gap around the beams.
Air is the best insulator. Why do you think insulation is so
light? What you are really buying is a structure to hold lots
of air.
Sheet metal is fine for this and is easy to work with. Make
a U-shaped shield that will fit around the bottom and
sides of the beam, with a 1 to 2 inch space between the
metal and the beam.
Porcelain insulators, used on electric fences, are good spacers
to keep the metal away from the wood. You could also
use 2" kiln posts or make your own spacers out of fired clay.
Just get a good-sized nail, 16 penny common or so, and run
it through the sheet metal, through the hole in the spacer,
and into the beam.
I would not recommend wrapping anything around or painting
anything on the beams. Remember, air is the best insulator,
and also the cheapest.
--
David Hendley
Maydelle, Texas
hendley@tyler.net
http://www.farmpots.com/
----- Original Message -----
From: Ruth Conway
To:
Sent: Wednesday, June 21, 2000 9:31 AM
Subject: preventing a wood fired kiln shed from burning down
| I built a wood kiln a little over a year ago and am concerned about
the
| possibility of eventually burning down the shed roof. The shed has no
walls
| and is built on a slope as is the kiln. From the top of the cantanary
arch
| (which has plenty of Kaowool and stucco)to the wooden cross beams is 18"
| and from the blow hole to the support beam is 30". It is the blow hole
which
| concerns me. Does any one have suggestions of ways to protect the cross
| beams under the blow hole? Concrete board? or would that trap heat and
| prevent moisture reaching the beams? Pin holes in the roof to let rain
seep
| onto the wood beams,but doesn't the flash point of wood lower with each
| firing regardless? What have those of you who have had wood kilns for a
| long time done. Should I just except a conflagration in years to come? I
| would like to prevent it...........Ruth Conway
| ________________________________________________________________________
| Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.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.
|
| |
|
