Peg Landham on thu 27 jul 00
Tom Joldersma writes...=20
" I assume that I should fill the gaps between the edges of the bricks =
in
the arch with mortar. "
This worries me. The concept of a catenary arch is that the bricks are =
cut to fit into a self-supporting arch. As I understand it, there =
shouldn't be much in the way of gaps between the bricks if it is built =
properly, should there? You don't want to be depending on mortar for =
holding that arch up. I've never built a kiln, so I don't know anything =
about it, actually. But when I designed a catenary arch for a science =
center once, it was supposed to be a self-supporting dry fit. I would =
like to build a kiln like this myself some day, so if somebody more =
experienced would jump in here...
-Oh, wait! I searched the archives for catenary arch and found quite a =
string. Check it out, Tom! They've already set us up for success! =
Thanks, once again, all you gregarious Clayarters!
Peg Landham, in Birmingham, where the competition for blood has driven =
the mosquitoes to develop mating plumage.
Tom Joldersma on thu 27 jul 00
Hello everyone,
I am considering building a propane-fired catenary arch kiln. However,
before I decide, I would like to find answers to a couple of questions. Can
anyone out there help me?
1) Is there (in actual use) a significant hot spot at the top caused by
focused radiation (as suggested by Niels Lou)? Is this any worse than the
hot spots along the edges and corners of a box-like kiln?
2) Should the front and rear walls be built outside or inside the arch? For
a small kiln (about 31 inches wide and 42 inches high), should one simply
omit the door and stack bricks in the front for each firing?
3) I assume that I should fill the gaps between the edges of the bricks in
the arch with mortar. What kind of mortar?
Thanks for any help,
Tom
philrogers pottery on thu 27 jul 00
Tom,
In answer to your questions:
1. In my experience ( 12 years with a catenary arch salt kiln) there is no
significant problem regarding a hot spot at the top of the kiln.
2. Yes, omitt the door. For a kiln of this size that is what I would do.
You will find access difficult otherwise. Build the back wall butting upto
the arch and not underneath.
3. I would try to build the arch with little or no mortar. If you do
decide to use a mortar then use it as thin as possible as soon as the bricks
are above the setting space. Your mortar depends on what you are intending
firing in the kiln and the bricks you are using to build with.
Hope this helps,
Phil.
----- Original Message -----
From: Tom Joldersma
To:
Sent: Thursday, July 27, 2000 2:13 PM
Subject: Catenary Arch
> Hello everyone,
>
> I am considering building a propane-fired catenary arch kiln. However,
> before I decide, I would like to find answers to a couple of questions.
Can
> anyone out there help me?
> 1) Is there (in actual use) a significant hot spot at the top caused by
> focused radiation (as suggested by Niels Lou)? Is this any worse than the
> hot spots along the edges and corners of a box-like kiln?
> 2) Should the front and rear walls be built outside or inside the arch?
For
> a small kiln (about 31 inches wide and 42 inches high), should one simply
> omit the door and stack bricks in the front for each firing?
> 3) I assume that I should fill the gaps between the edges of the bricks
in
> the arch with mortar. What kind of mortar?
>
> Thanks for any help,
>
> Tom
>
>
____________________________________________________________________________
__
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
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>
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melpots@pclink.com.
ferenc jakab on fri 28 jul 00
> 1) Is there (in actual use) a significant hot spot at the top caused by
> focused radiation (as suggested by Niels Lou)? Is this any worse than the
> hot spots along the edges and corners of a box-like kiln?
Niels may be right, but i have not found this to be the case in my 96cu'
catenary arch kiln, mytop and bottom temps are very even but I do fire over
20 -24 hrs at a 40 deg C ramp. (Large sculptural peices)
> 2) Should the front and rear walls be built outside or inside the arch?
For
> a small kiln (about 31 inches wide and 42 inches high), should one simply
> omit the door and stack bricks in the front for each firing?
One wall inside ande one wall outside. (Heat does not like to radiate around
corners) Same for front. Whether you build a permanent door or not depends
on your budget and engineering inclinations.
> 3) I assume that I should fill the gaps between the edges of the bricks
in
> the arch with mortar. What kind of mortar?
My mortar is 1 kaolin (Ekalite 1) to 3 Alumina hydrate and 2 silica. Makes a
good kiln wash too. I suspect its refractory properties are similar to ITC.
I dip the bricks into a thin slip of this mix. I have a thicker batch mixed
for evening out where the levels start to wander. this mortar has survived
firing to cone 11 and I was still able to take the kiln apart for
re-location.
Feri.
Back on line after a sytem rebuild due to a lightening spike. Autumn and
Monika, If you are still out there, could you send your E-mail adresses?
Dan Hill on sat 29 jul 00
Tom
I built a catenary arch kiln a couple of years ago which I fire to ^6-7
with propane. It is hard brick inside layer with IFB backup layer at the
ends and 3" of fiber blanket over the arch. I use this kiln for
soda-vapour glazing and have found no hot spots with this arrangment. It
fires within a 1/2 cone range throughout.
If you use a combination of straight and no. 1 and 2 arch brick you
will need virtually no mortar to create a free standing arch and I
reccommend that if you use mortar to use it very sparingly to avoid bits
of it dropping onto your pots during the firing. If on the other hand
you are building the arch with all straight bricks you will need to use
a filler mortar when laying up the arch. There are various recipes for
homemade mortars, check the archives.
Dan.
Wilno Ontario, Canada.
Tom Joldersma wrote:
>
> Hello everyone,
>
> I am considering building a propane-fired catenary arch kiln. However,
> before I decide, I would like to find answers to a couple of questions. Can
> anyone out there help me?
> 1) Is there (in actual use) a significant hot spot at the top caused by
> focused radiation (as suggested by Niels Lou)? Is this any worse than the
> hot spots along the edges and corners of a box-like kiln?
> 2) Should the front and rear walls be built outside or inside the arch? For
> a small kiln (about 31 inches wide and 42 inches high), should one simply
> omit the door and stack bricks in the front for each firing?
> 3) I assume that I should fill the gaps between the edges of the bricks in
> the arch with mortar. What kind of mortar?
>
> Thanks for any help,
>
> Tom
>
> ______________________________________________________________________________
> 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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