cg hayes on wed 11 jul 12
Dear Kiln Builders,
A friend of mine built a train kiln about 5 years ago. It's a joy to fire. =
Now we are planning to build a bourry box kiln with a sprung arch ware cham=
ber to concentrate more on glazed work. My question is about the step up be=
tween the firebox and the ware chamber. What purpose does the step have bey=
ond raising the floor to a more convenient height? The train seems to work =
well with no step at all. How much of a step does one need? There seems to =
be some variation.
Thanks,
Clarence
Des & Jan Howard on thu 12 jul 12
Clarence
As you say variation.
In our double Bourry box kiln the firebox floors & the
chamber floor were at the same height. Bag/baffle walls
went halfway up the kiln chamber, no gaps. There were
chequers, ala Cardew, extending below the kiln chamber,
then the central flue channel. The mousehole channels
did run beneath the firebox floors.
Des
On 12/07/2012 8:11 AM, cg hayes wrote:
> Now we are planning to build a bourry box kiln
> with a sprung arch ware chamber to concentrate more on glazed work.
> My question is about the step up between the firebox and the ware chamber=
.
> What purpose does the step have beyond raising the floor to a more conven=
ient height?
> The train seems to work well with no step at all.
> How much of a step does one need? There seems to be some variation.
--
Des & Jan Howard
Lue Pottery
Lue NSW
Australia
2850
02 6373 6419
www.luepottery.hwy.com.au
-32.656072 149.840624
tony clennell on thu 12 jul 12
Clarence: I fired our train for a dozen years and the part of the kiln
nearest the throat arch I referred to as "The Devil's Lunchbox" since those
pots got hammered with ash and were often very crusty. Lovely and crusty
that is. Those pots were often up to the shoulders in coals. I think one
could place a checkered bagwall at the throat if you wanted to protect the
pots from ash. Fact is you could probably place it anywhere along the
chamber if you wanted to protect the pots from the ash.
Perhaps Donavon Palmquist or Shane Mickey could chime in here. They are the
pros and have built many.
ciao,
Tony
On Thu, Jul 12, 2012 at 4:18 AM, Des & Jan Howard wrot=
e:
> Clarence
> As you say variation.
> In our double Bourry box kiln the firebox floors & the
> chamber floor were at the same height. Bag/baffle walls
> went halfway up the kiln chamber, no gaps. There were
> chequers, ala Cardew, extending below the kiln chamber,
> then the central flue channel. The mousehole channels
> did run beneath the firebox floors.
> Des
>
> On 12/07/2012 8:11 AM, cg hayes wrote:
>
>> Now we are planning to build a bourry box kiln
>> with a sprung arch ware chamber to concentrate more on glazed work.
>> My question is about the step up between the firebox and the ware chambe=
r.
>> What purpose does the step have beyond raising the floor to a more
>> convenient height?
>> The train seems to work well with no step at all.
>> How much of a step does one need? There seems to be some variation.
>>
>
> --
> Des & Jan Howard
> Lue Pottery
> Lue NSW
> Australia
> 2850
>
> 02 6373 6419
> www.luepottery.hwy.com.au
> -32.656072 149.840624
>
--
http://smokieclennell.blogspot.com
gary navarre on fri 13 jul 12
I'm by no means a pro at kiln build=3D
Thanks for asking Clarence, =3D0A=3D0A=3D0A=3DA0I'm by no means a pro at ki=
ln build=3D
ing yet, although I did make some money doing a workshop for some smart kid=
=3D
s by building them a trench kiln. I have however over the years been workin=
=3D
g on a cross draft Pignosed Bourry box designed around centenary arches wit=
=3D
h and without steps in the floor. The first version (30cu.ft.) and an elect=
=3D
ric conversion both had a step right up front with at least ^11 nicely glaz=
=3D
ed ware without much crusty ash from the throat arch. Most of the stuff was=
=3D
smooth and sold. When I took the kiln apart I discovered a major hot spot =
=3D
where the under floor (concrete block covered with firebrick) was damaged s=
=3D
o I figured if I rebuilt I'd eliminate the front step and use all that heat=
=3D
. When I finally rebuilt (60cu.ft.) I made the floor flat for 9' with no st=
=3D
eps and a good amount of room for ash to seep into the front bottom pots wi=
=3D
thout choking off the flow, once I got the mousehole opening big enough. Th=
=3D
at worked OK but the tail
wouldn't get hot like my earlier build and a lot of the pieces had more th=
=3D
an less ash that needed polishing. I've got some pretty neat crusty pieces =
=3D
too. After a visit with Jeff Cline in Cross Village and looking at his Anag=
=3D
ama with one step about half way through the chamber that I think might hel=
=3D
p compact the heat in the tail and give a spot for a decent secondary stoke=
=3D
coal pile to build and hold the heat up there so I can blast the glazes sm=
=3D
ooth, if I ever rebuild. Another tip Jeff and someone from Korea suggested =
=3D
is to set the floor shelves on an inch or two bricks off the bottom with no=
=3D
pieces seem to direct the ash under and out of the load. He also gave me a=
=3D
n 'at-a-boy' for the Pignose preheater idea and said he and the KIA still u=
=3D
se it to start the firing without having to stay lighting a bunch of little=
=3D
sticks all the time. If you are interested you will find just about everyt=
=3D
hing I know about the kiln I designed at
http://public.fotki.com/GindaUP/ca/kpap/=3DA0 Scroll down to the page bott=
om=3D
for a chronological start with the early drawings. There are also the tedi=
=3D
ously complete brick by brick stick by stick building and stoking videos on=
=3D
You Tube, all for free.If you can improve on any of the process have at it=
=3D
cause I'm done for a while.=3D0A=3D0A=3DA0=3D0AGary Navarre=3D0ANavarre Po=
ttery=3D0ANa=3D
varre Enterprises=3D0ANorway, Michigan, USA=3D0Ahttp://www.NavarrePottery.e=
tsy.=3D
com=3DA0=3DA0=3DA0=3DA0=3DA0 <...... New Pots=3D0Ahttp://www.youtube.com/Gi=
ndaUP=3D0Ahttp=3D
://public.fotki.com/GindaUP/=3D0A=3D0A=3D0A=3D0A___________________________=
_____=3D0A=3D
From: cg hayes =3D0ATo: Clayart@LSV.CERAMICS.ORG =
=3D0AS=3D
ent: Wednesday, July 11, 2012 5:11 PM=3D0ASubject: [Clayart] bourry box kil=
n=3D
=3D0A =3D0ADear Kiln Builders,=3D0AA friend of mine built a train kiln abou=
t 5 ye=3D
ars ago. It's a joy to fire. Now we are planning to build a bourry box kiln=
=3D
with a sprung arch ware chamber to concentrate more on glazed work. My que=
=3D
stion is about the step up between the firebox and the ware chamber. What p=
=3D
urpose does the step have beyond raising the floor to a more convenient hei=
=3D
ght? The train seems to work well with no step at all. How much of a step d=
=3D
oes one need? There seems to be some variation.=3D0A=3D0A=3D0AThanks,=3D0AC=
larence
jonathan byler on wed 18 jul 12
what is this trench you are talking about? the step, I understand. do
you have a link to a drawing that shows it?
On Jul 18, 2012, at 6:36 PM, douglas fur wrote:
> Clarence
>
> From my visit with Cardew I remember him emphasizing the trench
> being
> below the level of the firebox as causing negative pressure in the
> kiln
> chamber. This meant that in heavey reduction you wouldn't have flames
> leaping out to bite you. Comparing his kiln to a contemporary gas
> kiln
> for quietness and low drama his kiln was like "where's the fire and
> noise?"
>
> As for the step I've seen it in drawings in Bourry and historical
> drawings
> going back to the 1700's
>
> The extra distance would probably mean less ash getting to the ware
> so if
> that's what you're after- keep it.
>
> DRB
> Seola Creek
douglas fur on wed 18 jul 12
Clarence
From my visit with Cardew I remember him emphasizing the trench being
below the level of the firebox as causing negative pressure in the kiln
chamber. This meant that in heavey reduction you wouldn't have flames
leaping out to bite you. Comparing his kiln to a contemporary gas kiln
for quietness and low drama his kiln was like "where's the fire and noise?"
As for the step I've seen it in drawings in Bourry and historical drawings
going back to the 1700's
The extra distance would probably mean less ash getting to the ware so if
that's what you're after- keep it.
DRB
Seola Creek
Des & Jan Howard on thu 19 jul 12
Johnathon
Picture this:
kiln chamber floor at same level as firebox.
chequers, stacked brick, 3 layers, (4 1/2", 4 1/2", 4
1/2"). after Cardew, Pioneer Pottery 1969 p175.
central trench in floor leading to chimney.
So, chamber floor, then down 13 1/2" to kiln floor,
then 13 1/2" down to trench floor.
Des
On 19/07/2012 2:56 PM, jonathan byler wrote:
> what is this trench you are talking about? the step, I
> understand. do
> you have a link to a drawing that shows it?
--
Des & Jan Howard
Lue Pottery
Lue NSW
Australia
2850
02 6373 6419
www.luepottery.hwy.com.au
-32.656072 149.840624
douglas fur on sun 22 jul 12
CG/Jonathn
The best picture of this relationship is in Leach's potter's book.(as
designed by Mr. Baker...) In the cross section you can see that the level
of the grate is the same as the stacking floor. The checker, as Des
describes, is three layers- bricks on end, bricks on edge and bricks on
edge crosswise to those and set with gaps in a checkerwork pattern.
I noticed this relation ship skimming the kiln drawings in Leach, Bourry
and Cardew. The exception is the Singh kiln in Olsen which he notes as
firing unevenly. I imagine even firing is the reason these kilns were
built this way.
These monstrous brick piles (In Cardew's kiln the thickness of the bottom
half of the walls was about 3ft. thick. For no other eason than the bricks
were free for the hauling.) are out of date- the checker itself is 18" tall
so that's 20% of the potential interior volume given over to even heat
distribution.
Part of this design stems from moving enough air through the kiln to fire
off all that mass. The result is you need to back off the location of the
firebox so that the sweet spot of the flame is in the kiln. {Cardews kiln
would easily put 3ft of flames out the chimney in reduction. That's after
going from the firebox into the main chamber down six feet plus another
2-3ft through the cheker and trench, over 14-16ft to the second chamber
then rising 18-20ft. through the second and third chambers and out the
chiney...}
A modern IFB kiln will be different but I think the relationship of the
grate (or the bottom surface of hte wood on a hob) being level with the
setting floor would still be valid.
DRB
Seola Creek
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