Valerie Johnson on fri 1 jun 01
I am building the arch of my kiln out of hard straights, (against the advice of several who urge me to get arch bricks, which I am ignoring at my peril).
I assume I need to mortar the bricks in the arch. Do you put the whole arch together with chunks of refractory wedged in between the bricks, spring it and then mortar one by one? Or do you mortar as you lay the arch out on the frame? All advice is appreciated!
John Weber on sat 2 jun 01
Valerie, although I'm sure several folks on Clayart will offer excellent
suggestions, here is my 2 cents worth. I have built, rebuilt and rebuilt my
kilns with arch roofs without purchasing the set of arch bricks. My first
advice is if you can buy them, do so, its just easier. However, if you want
to save a few bucks and not do that, then here is what you need to do. You
have to cut two rows of skew brick and one row of key brick. If you don't
have a large 10" radial saw, borrow one or rent one. You want the type that
sits on a table. Before cutting any brick make a wooden form from a piece
of masonite and 2" x 2" wood stock or whatever you have available. The wood
is cut to form a frame for the masonite so it can be bent in the form of the
arch. The easiest way to attach the masonite to the frame is wood screws.
The size of the form should fit just inside the side walls and run the full
length back to the back wall of the kiln. The height of the arch is your
choice but I think much more than 6" to 8" creates too much arch for using
the straight bricks. Once you have the form cut and assembled, make sure
it fits inside the walls of the open kiln and the arch height is correct.
Then using the form, place regular bricks on it's arch, then where the arch
stops at the edge use another brick laying flat on the ground to estimate
the cut you need in order for the first brick (on the ground) to have a skew
cut adequate so the second brick lays flat on the arch form and butts evenly
to the skew brick. The bricks need to run long side front to back, not long
side across the kiln. Cut the skew brick (the brick that starts the row on
each side of the roof. Remember the skew brick needs some support, like a
metal bar running from the front to the back of the kiln at the row where
the skew bricks are placed. I built mine so the wall was 9" thick, laid in
one brick row and then a second skew brick row. This gives support and
leaves the angle of the skew bricks facing into the kiln right at the edge
of each side wall of the kiln. If you think the angle of your skew brick
works, go ahead and cut the rest of the skew bricks. Place your form by
supporting it with 2" x 4" stock or just stack up bricks to hold it level
with the top edge of the side walls. Place the skew bricks on the side walls
then start placing the roof bricks (straight) up the form. Leave the natural
gap at the top, this will be less than one brick thick so that you can cut
the "key" brick to fit. Lay all brick except the Key brick. Then you will
need to try to tighten the bricks as much as possible and estimate the
angles of the Key (top) brick. Cut it with the saw and place one in. If it
fits snugly go ahead and cut the others placing them as you go until
finished. Now you will need to fill in the small openings between the
bricks. You can do this with crumbled fire brick so the roof can be taken
apart later but I don't recommend it because the loose material seems to
come out when the bricks expand during the firing. I would get some kiln
cement and trowel it in between the gaps, let it set up for a day. Then pull
the form. If it falls in you will know you made a mistake saving a few
bucks, otherwise, voila!
By the way, if you are now totally confused get a copy of Robert
Piepenburg's book, "The Spirit of Clay". At page 382 he shows pictures and
gives better instructions for this roof. Good Luck. John Weber in
Manakin-Sabot, VA.
> -----Original Message-----
> From: Ceramic Arts Discussion List [mailto:CLAYART@LSV.CERAMICS.ORG]On
> Behalf Of Valerie Johnson
> Sent: Friday, June 01, 2001 8:01 PM
> To: CLAYART@LSV.CERAMICS.ORG
> Subject: building kiln arch
>
>
> I am building the arch of my kiln out of hard straights, (against
> the advice of several who urge me to get arch bricks, which I am
> ignoring at my peril).
> I assume I need to mortar the bricks in the arch. Do you put
> the whole arch together with chunks of refractory wedged in
> between the bricks, spring it and then mortar one by one? Or do
> you mortar as you lay the arch out on the frame? All advice is
> appreciated!
>
> __________________________________________________________________
> ____________
> 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.
>
Jennifer F Boyer on sat 2 jun 01
Can I add another question to Valerie's Question?
How do you keep the mortar in the arch from falling into the
pots. I imagine a lot of expansion and contraction over a number
of years leading to crumbling of mortar, which would have to be
thick(unlike the thin stuff in a flattop). I can't quite
imagine how this would be a good design for an arch, even if it
DID manage to keep from collapsing..
Jennifer
Valerie Johnson wrote:
>
> I am building the arch of my kiln out of hard straights, (against the advice of several who urge me to get arch bricks, which I am ignoring at my peril).
> I assume I need to mortar the bricks in the arch. Do you put the whole arch together with chunks of refractory wedged in between the bricks, spring it and then mortar one by one? Or do you mortar as you lay the arch out on the frame? All advice is appreciated!
>
> ______________________________________________________________________________
> 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.
--
~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*
Jennifer Boyer mailto:jboyer@adelphia.net
Thistle Hill Pottery
95 Powder Horn Glen Rd
Montpelier, VT 05602 USA
802-223-8926
http://www.thistlehillpottery.com/
Never pass on an email warning without checking out this site
for web hoaxes and junk:
http://urbanlegends.about.com/science/urbanlegends/cs/nethoaxes/index.htm
~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*
vince pitelka on sat 2 jun 01
Valerie said:
"I am building the arch of my kiln out of hard straights, (against the
advice of several who urge me to get arch bricks, which I am ignoring at my
peril).
I assume I need to mortar the bricks in the arch. Do you put the whole
arch together with chunks of refractory wedged in between the bricks, spring
it and then mortar one by one? Or do you mortar as you lay the arch out on
the frame? All advice is appreciated!"
It is a BAD idea to build an arch from straights, unless you are on a desert
island and all you have is straight bricks. I have a hard time
understanding why anyone would bother to go to all the trouble of building a
kiln, and then make the arch out of straights. I don't get it.
But, if there is no alternative, then make sure you use a very high quality
mortar that is designed to fill spaces, such as AP Green Greenpatch 421.
Apply the mortar as you lay the arch, and dip all the bricks in water before
you lay them in place and apply the mortar. A good mortar will fire hard
and strong, and should minimize mortar sifting down onto the wares. You
cannot eliminate this problem when you mortar the bricks, but at least if
you use a good quality commercial mortar it will minimize the problem. The
combined cost of the straights and the mortar will probably be more than the
proper arch bricks. I don't get it. Why would you do this?
Good luck -
- Vince
Vince Pitelka
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Home - vpitelka@dtccom.net
615/597-5376
Work - wpitelka@tntech.edu
615/597-6801 ext. 111, fax 615/597-6803
http://www.craftcenter.tntech.edu/
Paul Bailey / Janet Moe on sun 3 jun 01
Valerie,
Try to view a copy of the video by Graham Sheehan called "Building Your Own
Potters Kiln" by Tara Productions. He shows how to build an arch with straights and
does line the inside with fiber. Good Luck!
Janet, enjoying a cool but beautiful spring on the British Columbia coast
Mike Gordon wrote:
> If you must use straights for an arch, why not fiber the arch afterward,
> this would eliminate mortar sifting down on the ware. OR... put layer
> of kiln shelves across the last layer of work.
Mike Gordon on sun 3 jun 01
If you must use straights for an arch, why not fiber the arch afterward,
this would eliminate mortar sifting down on the ware. OR... put layer
of kiln shelves across the last layer of work. Mike Gordon
weaver on mon 4 jun 01
>>I am building the arch of my kiln out of hard straights, (against the
advice of several who urge me to get arch bricks, which I am ignoring at
my peril). I assume I need to mortar the bricks in the arch. Do you
put the whole arch together with chunks of refractory wedged in between
the bricks, spring it and then mortar one by one? Or do you mortar as
you lay the arch out on the frame? All advice is appreciated!<<
This picture is of our brick bread oven - not a kiln,
http://www.avalonrecords.com/brickoven/arch.html but it shows how an
arch works. Its a little hard to tell in the picture, but if you look up
underneath the arch you see no mortar - the bricks are very close
together. There is a wedge-shaped space between each one though that's
filled with fire-clay mortar (again - this is not a kiln, its a oven and
is only built to stand temperatures of around 1,000). The plywood form
is really two pices spaced with pieces of wood so one course of bricks
is built over then its moved forward, etc. The mortar was pushed down in
the crevices - it was not spread on the bricks first since the idea was
to get them as close together as possible at the inside of the arch.
Forest
Martin Howard on mon 4 jun 01
Traditionally in Victorian England, arches were made from soft rubbers. They
were so named because the soft red bricks were rubbed so that they fitted
exactly together over the wooden formwork arch. They were then taken out and
only a very thin paste of lime cement was put between them as they were
replaced for good. Virtually no cement can be seen from below. Those arches
have stood the test of time.
If the same method is used with rubbed, shaped, kiln bricks it should last a
similar time!!
Martin Howard
Webb's Cottage Pottery
Woolpits Road, Great Saling
BRAINTREE, Essex CM7 5DZ
England
martin@webbscottage.co.uk
http://www.webbscottage.co.uk
| |
|
