Pat Lindemann on thu 16 aug 07
So I am following Nils Lou's book "The Art of Firing" and building a chimney
for my 45 cu. ft catenary arch kiln. My question is this- is it common
practice to lay the bricks dry and then mortar over the outside of the
chimney? That is what I see being done in this book, but am wondering if
that makes the chimney air-tight enough. I looked at a couple of other
sites online with people building kilns and some seem to mortar each brick,
and some not- what is best?
Thank you.
Pat in SD, that would be South Dakota, where the end of the summer has
arrived...
Hank Murrow on thu 16 aug 07
On Aug 16, 2007, at 1:50 PM, Pat Lindemann wrote:
> So I am following Nils Lou's book "The Art of Firing" and building
> a chimney
> for my 45 cu. ft catenary arch kiln. My question is this- is it
> common
> practice to lay the bricks dry and then mortar over the outside of the
> chimney? That is what I see being done in this book, but am
> wondering if
> that makes the chimney air-tight enough. I looked at a couple of
> other
> sites online with people building kilns and some seem to mortar
> each brick,
> and some not- what is best?
Dear Pat;
A brick chimney swells and contracts with each firing; so joints open
up, and cold air can reduce useful draft. I suggest mortaring the
bricks, and additionally sheathing the flue with some heatproof
cladding tied at the corners with angle iron. You can use banding to
pull it all together...... like lumber is banded in the building yard.
The idea is to have a chimney that does not leak gases....... and
thus preserving draft.
Cheers, Hank
www.murrow.biz/hank
Paul Herman on thu 16 aug 07
Pat,
I recommend you mortar the chimney bricks. It takes more time, but
will result in better structural integrity. It also gives you the
opportunity to level and square each brick. The cheap and sleazy way
is usually not best. An outer plaster of mortar will eventually fall
of, causing the chimney to leak.
I hope you are building your kiln with an arch on top. An arch has
the most structural integrity for kilns.
best,
Paul Herman
Great Basin Pottery
Doyle, California US
http://greatbasinpottery.com
On Aug 16, 2007, at 1:50 PM, Pat Lindemann wrote:
> I looked at a couple of other
> sites online with people building kilns and some seem to mortar
> each brick,
> and some not- what is best?
>
> Thank you.
> Pat in SD, that would be South Dakota, where the end of the summer has
> arrived...
>
Eva Gallagher on thu 16 aug 07
Hi Pat - I just finished building a 13' chimney for a wood fired kiln - used
high temp mortar as I did not plan to put on any angle iron and was afraid
that it would fall over if I used just homemade stuff like fireclay and
grog. However I see from Hank's message that perhaps angle iron would be
good. In addition I thought I would put on some weatherproof mortar all over
the outside (we get lots of freezing and thawing here) - though don't know
quite what to use - the company that I got my mortar from does not carry
anything that would be weatherproof and the local hardware store does not
have anything that is heat resistant.
Regards,
Eva Gallagher
Deep River, Ontario
----- Original Message -----
From: "Hank Murrow"
To:
Sent: Thursday, August 16, 2007 8:04 PM
Subject: Re: mortaring kiln chimney?
> On Aug 16, 2007, at 1:50 PM, Pat Lindemann wrote:
>
>> So I am following Nils Lou's book "The Art of Firing" and building
>> a chimney
>> for my 45 cu. ft catenary arch kiln. My question is this- is it
>> common
>> practice to lay the bricks dry and then mortar over the outside of the
>> chimney? That is what I see being done in this book, but am
>> wondering if
>> that makes the chimney air-tight enough. I looked at a couple of
>> other
>> sites online with people building kilns and some seem to mortar
>> each brick,
>> and some not- what is best?
>
> Dear Pat;
>
> A brick chimney swells and contracts with each firing; so joints open
> up, and cold air can reduce useful draft. I suggest mortaring the
> bricks, and additionally sheathing the flue with some heatproof
> cladding tied at the corners with angle iron. You can use banding to
> pull it all together...... like lumber is banded in the building yard.
>
> The idea is to have a chimney that does not leak gases....... and
> thus preserving draft.
>
> Cheers, Hank
> www.murrow.biz/hank
>
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Gary Navarre on fri 17 aug 07
Hay Crew,
Way to go Eva, eh? If I recall refractory cements (castables?) have a
hardener that might make it more weather resistant. I'm still going for a
lag of kaolin, fireclay, kianite-mulite grog. Last time all I could afford
was fireclay and sand. One thing I found was I was as the kiln got hotter a
new leak would show color and I would patch it with a pinch of clay (lag).
After a few firings there were fewer cracks. I'm wondering if I could load a
caulking gun with lag and go round filling cracks as they develop. Part of
the key too is fire the kiln and that will harden the lag. A 9" thick double
wall, thinly lagged to keep it level, tapered brick stack should stand after
firing hot without angle iron. I am assuming the kiln chamber exit flue is
larger than the customary 9"x9" chimney exit. Cover the top when not in use
and it should last for quite a while. Have success and stay in there eh!
G in da U.P.
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