Remember that hodgepodge of boxed bricks and
displaced frogs? I wanted to see what I had, and how
much, and in what shape. (Some of the bricks from the
kiln we disassembled had actively growing green moss
on them, and came apart in chunks.) So I got my kids to
help me and we sorted bricks by high and low temp,
good and bad condition, wedge-shaped arch bricks of
various thicknesses and a few crumbly hulks.
So next on our cinderblock-tinfoil-sandwich
went a layer of lightweight, low temperature IFB
(insulating brick, made of clay and wood
shavings. The shavings fire out and leave a
brick "sponge".) I used a lot of the broken
bricks with still-mated halves in this layer.
Speaking of "Still mated", that's my very patient husband
on the left, helping me with the second layer of IFB -- a
sturdier, denser batch made for even higher temps. Notice
there's another foil layer between the soft bricks.
The top layer of the platform is high temperature
hard brick. Some of this will be the kiln floor. So,
from the ground up: cement, foil, low temp IFB,
foil, higher temp IFB, foil, hardbrick. Got it?  
Step Seven: Building the arch. This is the fun
part! Before you begin, you need a kiln form like
the one below, and at least three older relatives in
chairs with lemonade, who will tell you they don't
like this brick or that one in the place you've put it.  
The kiln form sits on four wooden wedges,
attached to long wires. When the arch is done,
these wedges will be yanked out, allowing the
arch to drop so it can be pulled out of the kiln.
The goal is to choose enough of some
angled or straight brick to form each
horizontal row, so that the inner edges of the
bricks echo the curve of the wooden form.
Straight brick rows will alternate with arch
brick rows, fatter arches with thinner arches.
Some arches are so subtle that you have to
study them closely to see that one edge is a
little narrower; others look like they were
sliced off a wheel of cheese. Stack, listen to
grandma, unstack, restack.

I should mention that I used the hardest
available brick for the bottom part of the
arch where the firebox will be -- hard brick,
or high temp softbrick. Sometimes I just had
to use what I had.
But once I got to that all-important keystone row, of course
nothing was just the right size. I unstacked and restacked
the rows leading up to it, and finally ended up sawing a few
bricks and grinding a few others to a point by rubbing them
on cinder blocks. Then the inner arch was done.
The second layer of arch was more of the same, only I was less picky about the bricks. The outer layer is really
just insulation for the inner layer. More cutting and grinding to make the keystones!
Step Eight: Taa-Daaa!
Somehow I don't have a photo of
the "moment of truth" when the
wedges are pulled, the wooden
form drops, we pull out the form
and the arch magically stands. I
have to say it impressed the
relatives, though.
Step Nine: front and back walls.  I tried to make sure
that any true hot spots -- the ports around burners, and
the walls where the fire will be flowing, and the base of
the chimney were all made of hard brick.

Because the kiln I learned on did it this way, I put one
burner in the right-front, and one in the left-rear. In
theory, it should get a "swirl" going inside the kiln, of
heat and then of soda.

The inner layer of the kiln door sits inside the arch itself.
It is hard brick, wedged at the edges with softer brick to
follow the shape of the arch. The actual door, the part
that is unbricked and rebricked each time I load, is two
bricks wide. I try to stagger bricks so I don't have a
"seam" up the middle, and every few rows I turn a brick
end-wise to interlock with the outer layer of door (made
of insulating brick and stacked in front of the arch, as
pictured below.) Two bricks jut out in the spots where I
have left a peep hole (just right of center) and a narrow
brick on the left can be pulled to add soda to the kiln in
mid firing.

I can already tell I will make changes in the stacking of
the door and front every time I load, changing the height
of the peeps and making other small adjustments. I was
really down to my last scraps of brick by the time I
finished the front.
Back wall, chimney and more: click here