jonathan byler on tue 30 sep 08
So we finally have a sort of go ahead with the final placement
location of our new soda kiln. I have laid out the foundation with a
layer of cinderblocks, holes facing upwards, and have cut the durock
concrete board to go over the top of that. There is some unevenness
in height of the cement blocks, although they do not rock and lay
flat on the cement foundation, which is pretty well flat. some of
the blocks stick up about an 1/8 - 3/16" in spots, and the concrete
board does not make contact completely in all spots, although when it
is weighed down, it seems relatively flat.
The construction of the kiln is going to be a layer of softbrick on
the floor, followed by a layer of hardbrick. The hardbrick inerior
walls will be built up with fireclay mortar to help keep things
level, softbrick is new and square and will be laid up dry outside of
that. Total kiln width is 63", total depth is 54" plus 9 inches of
hanging/sliding door in front. The slight extra width is to
accomodate removable firebox liners as suggest by hank murrow,
otherwise it would be closer to 58.5 wide by 54 deep.
I was wondering if we should put something between the durrock and
the cement blocks in order to bed it flat, or should we just try and
grind down the high spots? or just not worry about it?
also I was wondering if the hard brick floor should have fireclay
mortar between it and the softbrick underlayment, or should that be
laid up dry?
how much gap should be left in the hardbrick walls, if any to account
for expansion - total wall dimensions of the hardbrick interior will
be 54x45, give or take, since I will be enclosing the fireboxes at
the front with a permanent wall of hard brick under soft brick, and
the sliding door will overlap over that by 4.5 inches either side of
the front opening.
Final question for today: How big of a flue opening would you
recommend? The planned burners for this are going to be a pair of
300k btu/hr power burners total max heat input of 600k btu/hr. I was
thinking about making the flue opening about 45 sq inches, which is
the same size as our 600k btu/hr softbrick kiln, which is overall
larger in stacking space/interior dimensions. I was wanting to err
on the side of too large, since I can always stuff more bricks in to
close it up.
many thanks to all who have offered their help and advice on this
project so far.
best,
jon
jon byler
3-D Building Coordinator
Art Department
Auburn University, AL 36849
Vince Pitelka on wed 1 oct 08
Jon -
There is usually a little discrepancy in the height of cinder blocks, but I
do not recall seeing the amount you talk about. I think I would want to
knock down those high spots a bit, and I would use a big cup stone or
diamond wheel on a large angle grinder. Be sure to use a good dust mask and
face shield while doing the grinding. A little bit of discrepancy in height
is not a problem. The Durock is fiberglass-reinforced, and even if the
concrete block surface is slightly uneven there will be no structural
problem, but I would want the flattest possible surface for laying the
brick. I always lay the floor up dry.
I know that some people on Clayart believe in building kiln walls with no
connection between the inside 4.5" layer and the outside 4.5" layer, but I
would never do that myself. I always build kiln walls with a header course
(bricks penetrating the full 9" thickness of the wall) every four or five
stretcher courses. That ties the two layers together and makes a much more
stable wall. Of course, if your hard brick and soft brick are slightly
different sizes that can make it a bit difficult. If that is the case, one
option is to use a thin skim of mortar on whichever brick are slightly lower
in height.
1/8" expansion space every three or four hardbrick is fine. You don't need
to leave any expansion spaces with softbrick, but you might have to just to
get the bricks to line up.
With natural-draft burners, I usually use a flue opening cross section equal
to the total cross sections of all the burner ports. With two power
burners, you will have only two ports 4.5" by 5", and because the burners
are forcing the flames into the kiln under pressure, the same equation
doesn't work. I would go for a 9" by 9" flue opening on a kiln the size you
are building, and then you can always block it off part way if you need to.
Erring on the side of too large is never a problem. Erring on the side of
too small is a very serious problem. We have a 60 cubic foot salt kiln that
is due for replacement soon. We originally built it with a 9x9 flue and
chimney and have been fighting with it ever since. Next time I will know to
go oversize.
I hope this information is helpful.
- Vince
Vince Pitelka
Appalachian Center for Craft
Tennessee Tech University
vpitelka@dtccom.net; wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka
David Woof on wed 1 oct 08
Jon=2C you will be trapping excessive heat with no ventilation under the k=
iln with=20
your side placement of the blocks. Let this area breathe.
=20
First rule of good construction craftsmanship: start level and square. =20
Any lack of level and square at the beginning tends to magnify as you work.=
starting on=20
"good enough" and then fighting up hill from there to hold the line=2C=20
is unnessesary frustration and=2C will show up to haunt you at the finish.
=20
David______________________________________________________________________=
__
=20
<9. soda kiln construction questions for vince and others.Posted by: "jonat=
han byler" jebyler2@GMAIL.COM Date: Tue Sep 30=2C 2008 7:14 pm ((PDT)) ...I=
have laid out the foundation with alayer of cinderblocks=2C holes facing u=
pwards=2C and have cut the durockconcrete board to go over the top of that.=
There is some unevennessin height of the cement blocks=2C although they do=
not rock and layflat on the cement foundation=2C which is pretty well flat=
. some ofthe blocks stick up about an 1/8 - 3/16" in spots=2C and the concr=
eteboard does not make contact completely in all spots=2C although when iti=
s weighed down=2C it seems relatively flat.> =20
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Vince Pitelka on thu 2 oct 08
David Woof wrote:
"Jon, you will be trapping excessive heat with no ventilation under the
kiln with
your side placement of the blocks. Let this area breathe."
I don't want to revive this whole conversation about placing cinderblocks on
their sides versus placing them with the holes facing up, but I would like
to just repeat for Jon's sake that cinderblocks are MADE to be placed with
the holes facing up - that's how you place them if you want the greatest
support for whatever is on top of them. I have been involved in designing
and building kilns for four decades now, and I have come to a practice of
always placing the blocks facing upwards for stability and longevity,
because I do not trust the mix in cinderblocks these days and thus cannot
depend on their ability to support a heavy kiln if placed on their sides. I
generally build my kilns with two layers of softbrick and a hotface layer of
hardbrick in the floor, and there is never any problem with accumulation of
heat under the kiln.
I realize now that Jon said that he is just using a single layer of
softbrick in the floor, and I cannot attest to the amount of heat that would
pass through that single layer. Jon, if I were you I would go to two layers
of softbrick in the floor under the hotface layer of hardbrick.
- Vince
Vince Pitelka
Appalachian Center for Craft
Tennessee Tech University
vpitelka@dtccom.net; wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka
Edouard Bastarache on thu 2 oct 08
Hello aal,
" I don't want to revive this whole conversation about placing cinderblocks
on
their sides versus placing them with the holes facing up, but I would like
to just repeat for Jon's sake that cinderblocks are MADE to be placed with
the holes facing up - that's how you place them if you want the greatest
support for whatever is on top of them.
Vince"
That is what they do on the bottom of 150-ton steel furnaces,
why not do like the steelmakers.
Gis la revido
Edouard Bastarache
Spertesperantisto
Sorel-Tracy
Quebec
Canada
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James F on thu 2 oct 08
Jon...
The students at the local college built a salt/soda kiln modeled after the =
one at San Diego State University. I welded up the frame for it=2C but was=
not involved in the planning nor construction other than obtaining a copy =
of the original SDSU plans.
This kiln is approximately 50 cubic feet. It is fired with two of the larg=
e Ward Power Burners=2C and has a flue of 81 square inches (9x9). It fires=
extremely well with these specifications.
As Vince stated=2C I think it is extremely important to incorporate hard ti=
e bricks that run across both the inside and outside walls. The college ki=
ln was built with very few of these=2C as they were afraid of heat loss. W=
ith each firing=2C the hard brick inner walls remained tight=2C straight=2C=
and true=2C but the outside IFB walls puffed out=2C and never returned com=
pletely to their original position. Therefore=2C with each firing=2C the p=
roblem was exacerbated. At this point=2C with only 20 or 30 firings=2C the=
kiln needs to be rebuilt. The inner walls are still nearly perfect=2C but=
the outer IFB shell is ready to fall out completely. I am not even sure w=
hat is holding it up! My original thought on rebuilding the kiln was to in=
corporate two or three tie bricks on every row=2C or perhaps every other ro=
w=2C but Vince's idea of a complete tie course every 4 or 5 rows is somethi=
ng I will have to consider.
I also agree with those who implore you to level the base before proceeding=
. Grinding would work=2C but is a big job. The gentleman who designed and=
built the SDSU kiln provided me with a recipe for what he calls "leveling =
slurry" which might be another option. He specifies 1 part fine sand=2C 1 =
part fine grog=2C 2 parts Goldart clay=2C and a few drops of sodium silicat=
e. He said to apply thinly to damp brick or block. I would be afraid=2C h=
owever=2C that it would break down over time and filter between the blocks=
=2C causing an even bigger problem down the road. Also=2C since you instal=
led your block with the holes facing up=2C it seems as though any type of l=
eveling compound would be out.
The option which we employed at the college was to pour a very flat and lev=
el secondary slab directly atop the uneven concrete floor=2C then to lay th=
e block atop this level secondary slab. We figured that this would be a mu=
ch longer term solution than would a leveling compound=2C and much easier t=
han grinding. Also=2C with a grinder you have a reasonable chance of makin=
g things worse rather than better.
I do not believe letting the Durock simply bridge the unevenness is an opti=
on=2C as Durock is quite flexible and will eventually conform to the substr=
ate.
I hope this helps. Good luck with your project.
...James
_________________________________________________________________
Stay up to date on your PC=2C the Web=2C and your mobile phone with Windows=
Live.
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jonathan byler on fri 3 oct 08
thanks to all who have replied.
I mixup mortar, and place the durock on top of the mortar topped
cement blocks. with some extra bricks placed on top to hold
everything down, I should be able to get a nice bearing surface for
the durock, upon which I can build the rest of the kiln. if it is
still uneven, I will use some leveling compound or very thin mortar
under the first layer of the floor.
Is there any reason that I will need more than a layer of soft brick
and a layer of hardbrick for the floor, or should I do three layers
total? I am probably going to place tie in bricks across the wall,
but more staggered throughout the wall than a single course every 5.
I also planned to place diagonal reinforcement in the frame to keep
it from bulging in the middle if this proves to be a problem.
jon byler
3-D Building Coordinator
Art Department
Auburn University, AL 36849
On Oct 2, 2008, at 12:39 PM, James F wrote:
> Jon...
>
> The students at the local college built a salt/soda kiln modeled
> after the one at San Diego State University. I welded up the frame
> for it, but was not involved in the planning nor construction other
> than obtaining a copy of the original SDSU plans.
>
> This kiln is approximately 50 cubic feet. It is fired with two of
> the large Ward Power Burners, and has a flue of 81 square inches
> (9x9). It fires extremely well with these specifications.
>
> As Vince stated, I think it is extremely important to incorporate
> hard tie bricks that run across both the inside and outside walls.
> The college kiln was built with very few of these, as they were
> afraid of heat loss. With each firing, the hard brick inner walls
> remained tight, straight, and true, but the outside IFB walls
> puffed out, and never returned completely to their original
> position. Therefore, with each firing, the problem was
> exacerbated. At this point, with only 20 or 30 firings, the kiln
> needs to be rebuilt. The inner walls are still nearly perfect, but
> the outer IFB shell is ready to fall out completely. I am not even
> sure what is holding it up! My original thought on rebuilding the
> kiln was to incorporate two or three tie bricks on every row, or
> perhaps every other row, but Vince's idea of a complete tie course
> every 4 or 5 rows is something I will have to consider.
>
> I also agree with those who implore you to level the base before
> proceeding. Grinding would work, but is a big job. The gentleman
> who designed and built the SDSU kiln provided me with a recipe for
> what he calls "leveling slurry" which might be another option. He
> specifies 1 part fine sand, 1 part fine grog, 2 parts Goldart clay,
> and a few drops of sodium silicate. He said to apply thinly to
> damp brick or block. I would be afraid, however, that it would
> break down over time and filter between the blocks, causing an even
> bigger problem down the road. Also, since you installed your block
> with the holes facing up, it seems as though any type of leveling
> compound would be out.
>
> The option which we employed at the college was to pour a very flat
> and level secondary slab directly atop the uneven concrete floor,
> then to lay the block atop this level secondary slab. We figured
> that this would be a much longer term solution than would a
> leveling compound, and much easier than grinding. Also, with a
> grinder you have a reasonable chance of making things worse rather
> than better.
>
> I do not believe letting the Durock simply bridge the unevenness is
> an option, as Durock is quite flexible and will eventually conform
> to the substrate.
>
> I hope this helps. Good luck with your project.
>
> ...James
>
> _________________________________________________________________
> Stay up to date on your PC, the Web, and your mobile phone with
> Windows Live.
> http://clk.atdmt.com/MRT/go/msnnkwxp1020093185mrt/direct/01/
David Woof on sat 4 oct 08
________________________________________________________________________Vin=
ce=2C Jon=2C others=2C
=20
I agree=2C let's not start the "blocks debate" again. Vince=2C myself=2C =
and respected others=2C covered this topic some time ago=2C now worth readi=
ng in the archives. While we see things differently on some minor points=
=2C there is a long history of well built kilns and effective firing method=
s between us collectively.
=20
My preference is to not use cinder block at all but use the highest rated c=
oncrete blocks and as Vince just advised=2C protect from heat with ample in=
sulation. Again the archives cover the pros and cons.=20
=20
Jon=2C best of everything=2C=20
=20
David
=20
<<<8a. Re: soda kiln construction questions for vince and others.Posted by:=
"Vince Pitelka" vpitelka@DTCCOM.NET Date: Thu Oct 2=2C 2008 10:45 am ((PDT=
)) David Woof wrote:"Jon=2C you will be trapping excessive heat with no ven=
tilation under thekiln withyour side placement of the blocks. Let this area=
breathe." I don't want to revive this whole conversation about placing cin=
derblocks ontheir sides versus placing them with the holes facing up=2C but=
I would liketo just repeat for Jon's sake that cinderblocks are MADE to be=
placed withthe holes facing up - that's how you place them if you want the=
greatestsupport for whatever is on top of them. I have been involved in de=
signingand building kilns for four decades now=2C and I have come to a prac=
tice ofalways placing the blocks facing upwards for stability and longevity=
=2Cbecause I do not trust the mix in cinderblocks these days and thus canno=
tdepend on their ability to support a heavy kiln if placed on their sides. =
Igenerally build my kilns with two layers of softbrick and a hotface layer =
ofhardbrick in the floor=2C and there is never any problem with accumulatio=
n ofheat under the kiln. I realize now that Jon said that he is just using =
a single layer ofsoftbrick in the floor=2C and I cannot attest to the amoun=
t of heat that wouldpass through that single layer. Jon=2C if I were you I =
would go to two layersof softbrick in the floor under the hotface layer of =
hardbrick.- Vince =20
_________________________________________________________________
See how Windows connects the people=2C information=2C and fun that are part=
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James F on sat 4 oct 08
Jon...
>=20
> Is there any reason that I will need more than a layer of soft brick
> and a layer of hardbrick for the floor=2C or should I do three layers
> total?
Both the SDSU kiln plans and the kiln at the local college have two layers =
of K23 IFB beneath the hard brick. I don't know if it is "necessary"=2C bu=
t it is there. Is it really worth taking a chance just to save $300 (or 3"=
in height) on what is likely going to be a $6000 investment?
> I also planned to place diagonal reinforcement in the frame to keep
> it from bulging in the middle if this proves to be a problem.
As great grandma said about chicken soup=2C "It vouldn't hoit!" When I vis=
ited the college kiln recently=2C I saw that someone had booger-welded some=
metal bracing spaced out from the frame across some of the bulging areas (=
not a pretty sight) in an attempt to stave off the inevitable. It looks li=
ke it hasn't been fired since the metal has been installed (no rust or spal=
ling)=2C so I do not know if it will do any good=2C especially at this late=
stage.
This is all just my opinion or what I have seen=2C and is absolutely not go=
spel. Others on this list have far=2C far more experience than I=2C so ult=
imately I defer to them.
Good luck.
...James
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