I am in the process of building a new kiln. It is a 9 meter long snake kiln. This picture shows
where the kiln will go. It was taken before I cleared out the wood that is behind the green
folding chair in the picture. You can see the chimney in the background of my main climbing
kiln. It is the reddish pipe sticking out of the brick stack. To the right of that is the steel
chimney of my small kerosene kiln. I mainly use the kerosene kiln for firing the cups I use when
I have an event I run that is a very cheap under-glaze painting workshop. I do it as volunteer
where the kiln will go. It was taken before I cleared out the wood that is behind the green
folding chair in the picture. You can see the chimney in the background of my main climbing
kiln. It is the reddish pipe sticking out of the brick stack. To the right of that is the steel
chimney of my small kerosene kiln. I mainly use the kerosene kiln for firing the cups I use when
I have an event I run that is a very cheap under-glaze painting workshop. I do it as volunteer
The picture below is the plan for the kiln. I haven't worked from plans in the past. This time I
want to make sure I get the slope right. The rise is actually only half of what I have written. It
will rise 11.5 cm. per level. I have a 40 cm rise from the fire box to the first level and will have a
total rise of 30 cm after the exit flues in two steps. I am not building in a true "empty" room
after the exit flues but there will be an empty chamber to stabilize the air flow. I am planning on
using a steel chimney for the final area.
want to make sure I get the slope right. The rise is actually only half of what I have written. It
will rise 11.5 cm. per level. I have a 40 cm rise from the fire box to the first level and will have a
total rise of 30 cm after the exit flues in two steps. I am not building in a true "empty" room
after the exit flues but there will be an empty chamber to stabilize the air flow. I am planning on
using a steel chimney for the final area.
This picture shows the area just before the leveling out of the floor begins. I have put two
runners in on both sides, originally for a different purpose. They came in very handy for using
as levelers for the cross wood. I first leveled the cross wood closest to the bottom of the
picture. I then leveled the other cross wood so it was level cross wise and level with the other
cross wood. The yellow level in the picture is being used to make sure the second cross wood
is level with the first. I attached the wood to the runners with screws. Cutouts are visible in the
cross wood at the bottom. The cutouts are so I can use shorter anchor screws.
runners in on both sides, originally for a different purpose. They came in very handy for using
as levelers for the cross wood. I first leveled the cross wood closest to the bottom of the
picture. I then leveled the other cross wood so it was level cross wise and level with the other
cross wood. The yellow level in the picture is being used to make sure the second cross wood
is level with the first. I attached the wood to the runners with screws. Cutouts are visible in the
cross wood at the bottom. The cutouts are so I can use shorter anchor screws.
The picture below shows a detail of the form for leveling a single level of floor. I have already
put both the upper and lower cross pieces of wood in place and leveled them. I should note
that the width of the frame on all dimensions is larger than the finished size. I purposefully
have included an extra 20 cm. of width on both sides and about an extra 10 cm. on the length
side so that I have some room to maneuver the leveling form. If you put both your length and
width forms in exactly to finished size you will not only undermine your stakes holding in your
forms but you will have a lot of headaches because there is no room to work.
put both the upper and lower cross pieces of wood in place and leveled them. I should note
that the width of the frame on all dimensions is larger than the finished size. I purposefully
have included an extra 20 cm. of width on both sides and about an extra 10 cm. on the length
side so that I have some room to maneuver the leveling form. If you put both your length and
width forms in exactly to finished size you will not only undermine your stakes holding in your
forms but you will have a lot of headaches because there is no room to work.
Below you can see the frame that gives the finished floor elevation. In this image I have dug
out a little of the dirt so that the frame rests on its two guides on the left and right. I chose the
design out of necessity. It would have been easier to have a piece of wood at the bottom to
give an even reading. To have four pieces of wood like I do it is easy to get an uneven floor
between the wood guides. The simple reason I didn't use a piece of wood along the bottom is I
didn't have one handy and didn't want to cut a much longer piece to fit. This design let me
adjust the depth easily.
out a little of the dirt so that the frame rests on its two guides on the left and right. I chose the
design out of necessity. It would have been easier to have a piece of wood at the bottom to
give an even reading. To have four pieces of wood like I do it is easy to get an uneven floor
between the wood guides. The simple reason I didn't use a piece of wood along the bottom is I
didn't have one handy and didn't want to cut a much longer piece to fit. This design let me
adjust the depth easily.
This shows another close up of the frame. As I moved the main frame to different sections of
the kiln I unscrewed the four boards and adjusted them to fit my desired finished floor
elevation. I had a drop of 13 cm per section. As I got down to the lower ends of the kiln this
kind of frame got a little unwieldy as the finished floor elevation was about 70-90 cm below the
guide. One thing I did that isn't really visible in these photos is to put in a finished floor stake
at elevation. That is to say after I had finished digging out the floor I then drove a stake into
the dirt, leaving the top of it at the correct elevation. This way I had a record of the right height
as I moved on.
the kiln I unscrewed the four boards and adjusted them to fit my desired finished floor
elevation. I had a drop of 13 cm per section. As I got down to the lower ends of the kiln this
kind of frame got a little unwieldy as the finished floor elevation was about 70-90 cm below the
guide. One thing I did that isn't really visible in these photos is to put in a finished floor stake
at elevation. That is to say after I had finished digging out the floor I then drove a stake into
the dirt, leaving the top of it at the correct elevation. This way I had a record of the right height
as I moved on.
Another detail of the frame. In this picture below I have scooped out the dirt and the movable
part of the frame is resting on the cross bars. I will now dig out the dirt and slowly move the
frame along, using it as a check for floor height. I can't really offer a better way to level the
floor although there are many ways to do it. The frame I have made is a little heavy to move.
Anything lighter would make it difficult to stabilize. The total length of one of the floor sections
is roughly 100 cm, or about 36 inches. The total width is roughly 120 cm. or about 47 inches. I
am not exact with these intermediate measurements. I try to keep the overall length to what I
want and the width consistent.
part of the frame is resting on the cross bars. I will now dig out the dirt and slowly move the
frame along, using it as a check for floor height. I can't really offer a better way to level the
floor although there are many ways to do it. The frame I have made is a little heavy to move.
Anything lighter would make it difficult to stabilize. The total length of one of the floor sections
is roughly 100 cm, or about 36 inches. The total width is roughly 120 cm. or about 47 inches. I
am not exact with these intermediate measurements. I try to keep the overall length to what I
want and the width consistent.
Below I am showing the kiln, almost all dug out, from the lowest area. I still have to dig out the
top "extra room". I also have to dig out the lowest firebox area. If you look at the bottom of the
picture in the middle of the flat area you can see the top of a stake that has been driven into
the ground. Look just above the brick, just to the right of the tape measure. That is the
elevation stake I wrote about a couple of pictures above. As you dig and move forms around it
is easy to lose your reference points. Having a finished floor stake helps out in that sense. I
have put a brick on the edge of each level just to illustrate distance and elevation difference
solely for this picture. The width of the excavated portion is roughly 150 cm.
top "extra room". I also have to dig out the lowest firebox area. If you look at the bottom of the
picture in the middle of the flat area you can see the top of a stake that has been driven into
the ground. Look just above the brick, just to the right of the tape measure. That is the
elevation stake I wrote about a couple of pictures above. As you dig and move forms around it
is easy to lose your reference points. Having a finished floor stake helps out in that sense. I
have put a brick on the edge of each level just to illustrate distance and elevation difference
solely for this picture. The width of the excavated portion is roughly 150 cm.
This another picture taken from the top of the excavation pit. The depth of the pit at the
deepest point in this picture is about 70 cm. I will dig one more section that will be about 110
cm. deep. The main tool I used was a steel bar. It helped get the sides straight. I had an offer
from a local business man to have him come in and excavate the entire kiln out with a back
hoe. I would usually jump at an offer like that but this being Japan I decided there would be too
intricate a web of obligations spun if I took him up so just dug it by hand. I piled all the dirt up
on one side. I will probably use all the dirt in another part of my yard. It seems to be very rich
soil. A shame to put it back on the kiln.
deepest point in this picture is about 70 cm. I will dig one more section that will be about 110
cm. deep. The main tool I used was a steel bar. It helped get the sides straight. I had an offer
from a local business man to have him come in and excavate the entire kiln out with a back
hoe. I would usually jump at an offer like that but this being Japan I decided there would be too
intricate a web of obligations spun if I took him up so just dug it by hand. I piled all the dirt up
on one side. I will probably use all the dirt in another part of my yard. It seems to be very rich
soil. A shame to put it back on the kiln.
You can see the dirt on the left side of the picture. At this point in the work I will start putting in
the sub-floor. I used a mixture of a clay bearing "soil" I have in abundance around my house in
a ratio of 5 clay, 2 portland cement to 2 water. I tried less water, around 1.5, in the same ratio
but only got a spinning mass of material in the mixer. I had to add the last .5 to get the mixer to
properly cut through the mixture and mix. A note on using clay bearing soil. It is best to mix it
in the mixer for 10 minutes or so, until it is broken down and starts to form small pellets. The
concrete will then coat each pellet more uniformly. I found If the water content in the clay was
high I needed to add less water.
the sub-floor. I used a mixture of a clay bearing "soil" I have in abundance around my house in
a ratio of 5 clay, 2 portland cement to 2 water. I tried less water, around 1.5, in the same ratio
but only got a spinning mass of material in the mixer. I had to add the last .5 to get the mixer to
properly cut through the mixture and mix. A note on using clay bearing soil. It is best to mix it
in the mixer for 10 minutes or so, until it is broken down and starts to form small pellets. The
concrete will then coat each pellet more uniformly. I found If the water content in the clay was
high I needed to add less water.
Another view from the other side. The pile of bricks show just a sample of three truck loads I
bought to use as a sub-floor. I am planning on using a concrete/clay mix for one section of the
sub floor. I will put a layer of these used red bricks on top of that. Finally I will put the fire brick
on top of that. I am very concerned about the dampness of the ground and how it will affect
the ware. This area is damp so I have decided on the double sub floors. When I initially laid
out the kiln I picked an elevation at the top that was near natural grade so I didn't have to
have any infill areas. Infill is usually less stable for kiln floors or supporting walls.
bought to use as a sub-floor. I am planning on using a concrete/clay mix for one section of the
sub floor. I will put a layer of these used red bricks on top of that. Finally I will put the fire brick
on top of that. I am very concerned about the dampness of the ground and how it will affect
the ware. This area is damp so I have decided on the double sub floors. When I initially laid
out the kiln I picked an elevation at the top that was near natural grade so I didn't have to
have any infill areas. Infill is usually less stable for kiln floors or supporting walls.
I am building the kiln in tight confines. There isn't any room on the length axis. In fact I will
have to extend the roof to meet my workshop, visible in the background. On the chimney end I
have measured from the road back so the prefabricated chimney won't block cars coming in
and out. On both sides of the kiln it is a little tight. The left of this pictures shows a wall of
wood, the right looks more open but only has enough room for wood for one firing. This kind
of kiln uses roughly 40% more wood for its size than other kilns. At the end of the firing wood
is stacked up to the roof in the kiln which accounts for some of the extra usage.
have to extend the roof to meet my workshop, visible in the background. On the chimney end I
have measured from the road back so the prefabricated chimney won't block cars coming in
and out. On both sides of the kiln it is a little tight. The left of this pictures shows a wall of
wood, the right looks more open but only has enough room for wood for one firing. This kind
of kiln uses roughly 40% more wood for its size than other kilns. At the end of the firing wood
is stacked up to the roof in the kiln which accounts for some of the extra usage.
The picture below shows one of my main planning tools. I see how big the kiln has to be to fit
the shelves I have on hand. I left space between what will be stacks of ware to drop in wood
and then used the measurements to determine the overall size. I will have room for a four shelf
stack, stoking area and then the next stack area. I was told by a guy I used to buy my bricks
from that this was silly beyond belief as a way to plan kilns. I will note I am building this kiln with
the extra bricks he sold me when I gave him the dimensions for my first kiln and let him figure
the brick count. I know a few Japanese that use this method to plan big kilns.
the shelves I have on hand. I left space between what will be stacks of ware to drop in wood
and then used the measurements to determine the overall size. I will have room for a four shelf
stack, stoking area and then the next stack area. I was told by a guy I used to buy my bricks
from that this was silly beyond belief as a way to plan kilns. I will note I am building this kiln with
the extra bricks he sold me when I gave him the dimensions for my first kiln and let him figure
the brick count. I know a few Japanese that use this method to plan big kilns.
This shows the overall image with the shelves in place for two of the stacking areas. In the
foreground are the two stakes for the next two areas. When the kiln is finished this will be,
counting from the bottom of the picture below the 1st. 2nd. 3rd. 4th. ware areas. There are
two more areas that will go in towards the top of the picture. Not visible is the stoking area.
foreground are the two stakes for the next two areas. When the kiln is finished this will be,
counting from the bottom of the picture below the 1st. 2nd. 3rd. 4th. ware areas. There are
two more areas that will go in towards the top of the picture. Not visible is the stoking area.
This is a picture of the machine I use to mix my concrete/clay mixture. It holds about 5 buckets
of clay, 2 buckets of Portland cement and 2 buckets of water. I mix the clay first to break it up
and keep mixing till it starts forming into round balls. This usually starts to happen after about
10 minutes of mixing. I then add the two buckets of cement and let it mix for another few
minutes. The water is then added and mixed. After the water is added I try to have the mixture
in the forms in less than 30 minutes. More than that and it starts to firm up and is less plastic.
One mixer load is enough to do one level of the floor.
of clay, 2 buckets of Portland cement and 2 buckets of water. I mix the clay first to break it up
and keep mixing till it starts forming into round balls. This usually starts to happen after about
10 minutes of mixing. I then add the two buckets of cement and let it mix for another few
minutes. The water is then added and mixed. After the water is added I try to have the mixture
in the forms in less than 30 minutes. More than that and it starts to firm up and is less plastic.
One mixer load is enough to do one level of the floor.
The usual proportions for concrete are not 5-2-2. I substituted out the aggregate and sand for
clay. I have added a little more concrete than would be usual. The water proportion is where I
have really tried to be careful as too much stops the chemical reaction that cures concrete
and you end up with a slightly soft mixture that isn't really good for anything. The compressive
strength of this mixture looks like it should be enough but time will be the judge of that. On
almost the entire length of the kiln I have dirt buttressing the "ramp" that will hold the arch.
There is only one area around the chimney where the clay isn't sided by dirt.
clay. I have added a little more concrete than would be usual. The water proportion is where I
have really tried to be careful as too much stops the chemical reaction that cures concrete
and you end up with a slightly soft mixture that isn't really good for anything. The compressive
strength of this mixture looks like it should be enough but time will be the judge of that. On
almost the entire length of the kiln I have dirt buttressing the "ramp" that will hold the arch.
There is only one area around the chimney where the clay isn't sided by dirt.
The picture below shows something that didn't work out well. If you look at the scene in the
picture below from the lower end of the kiln you would see 6 flat concrete covered levels but
the front of each level would have dirt visible under the concrete. I wanted to seal the dirt in for
a number of reasons. I tried in the level pictured below to put brick on the face, planning to
hold the bricks in place with the concrete. The form below shows a frame for holding the bricks
in place. This particular level also had the challenge of having a stepped floor. It is the
"sutema". That is the flow evening or regulating area at the back of the kiln. No ware is put in
here.
picture below from the lower end of the kiln you would see 6 flat concrete covered levels but
the front of each level would have dirt visible under the concrete. I wanted to seal the dirt in for
a number of reasons. I tried in the level pictured below to put brick on the face, planning to
hold the bricks in place with the concrete. The form below shows a frame for holding the bricks
in place. This particular level also had the challenge of having a stepped floor. It is the
"sutema". That is the flow evening or regulating area at the back of the kiln. No ware is put in
here.
This picture shows the level pictured above from a different angle. The part in the left side of
the picture is the stepped area. A transverse wall will provide the upper limit of the firing
chamber. It will rest on the lower part of this level's steps. The exit flues will be in the bottom of
this wall. The part of the step in the right of this picture is a dead air space that is necessary to
calm the air flow before it heads up the chimney. Without this area the velocity of the air out
the exit flues would be so high it would create a kind of temperature vacuum that would lower
the temperature in the back of the kiln. This strategy will help with this problem.
the picture is the stepped area. A transverse wall will provide the upper limit of the firing
chamber. It will rest on the lower part of this level's steps. The exit flues will be in the bottom of
this wall. The part of the step in the right of this picture is a dead air space that is necessary to
calm the air flow before it heads up the chimney. Without this area the velocity of the air out
the exit flues would be so high it would create a kind of temperature vacuum that would lower
the temperature in the back of the kiln. This strategy will help with this problem.
In theory the bricks are supposed to form the front of the step of these two levels. What
happened in practice is the concrete/clay mixture developed cracks in the two levels where I
tried this. If you look down to the fifth and eighth pictures below counting the picture below you
will see the brick fronting and the cracks that have developed after the mixture dried. The
cracking won't be a structural problem I don't believe but it doesn't look nice and would have
been better had it not developed. I wouldn't recommend changing anything in the construction
of a level like the one below except to not use brick in this fashion.
happened in practice is the concrete/clay mixture developed cracks in the two levels where I
tried this. If you look down to the fifth and eighth pictures below counting the picture below you
will see the brick fronting and the cracks that have developed after the mixture dried. The
cracking won't be a structural problem I don't believe but it doesn't look nice and would have
been better had it not developed. I wouldn't recommend changing anything in the construction
of a level like the one below except to not use brick in this fashion.
One problem I had is removing the frame wood pictured on the right in the picture below. It is
held in place by screws that are just visible in the lower right part of the wood. After I had
poured the concrete for the top level the screws were no longer accessible from the upper
level. I could have just left the wood in place as it was flush with the finished surface and it
would have burned out during the subsequent firings of the kiln. Instead I applied a propane
torch to the area around the screw and burned the wood out so the screw just fell out. I was
then able to remove the wood and only have the empty strip left where it had been.
held in place by screws that are just visible in the lower right part of the wood. After I had
poured the concrete for the top level the screws were no longer accessible from the upper
level. I could have just left the wood in place as it was flush with the finished surface and it
would have burned out during the subsequent firings of the kiln. Instead I applied a propane
torch to the area around the screw and burned the wood out so the screw just fell out. I was
then able to remove the wood and only have the empty strip left where it had been.
This is another overview of the levels, concrete in place, before I started putting in the second
sub-floor. I put in the second sub-floor more as a buttress for the forms that held in the "ramp"
forms for the arch. I couldn't drive stakes through this floor to hold the forms. The cracks I
wrote about above are just visible in the lower right level. They are small in this picture but
gradually got larger. The second level from the right, the left leading edge, was not poured to
its full width. It could have been extended another 20 cm. to the left in this picture. I filled it out
in subsequent pourings but it is better to get the full width on the first pouring.
sub-floor. I put in the second sub-floor more as a buttress for the forms that held in the "ramp"
forms for the arch. I couldn't drive stakes through this floor to hold the forms. The cracks I
wrote about above are just visible in the lower right level. They are small in this picture but
gradually got larger. The second level from the right, the left leading edge, was not poured to
its full width. It could have been extended another 20 cm. to the left in this picture. I filled it out
in subsequent pourings but it is better to get the full width on the first pouring.
This is a view of the bottom of the kiln as I am breaking out the final area around the firebox. I
decided to not put in the concrete/clay mix for the firebox portion. I will only use firebricks.
There are a number of reasons for this. The mixture won't hold up to the temperatures so I will
have to face it in all areas of the kiln with fire brick. This won't be a problem in most areas
because the height of the mixture allows it to be covered by one layer of brick. In the firebox
the drop-off is 40 cm. or so meaning I will have to stack a number of bricks to get a fireproof
facing. With that being the case I might as well just build the arch support out of firebrick.
decided to not put in the concrete/clay mix for the firebox portion. I will only use firebricks.
There are a number of reasons for this. The mixture won't hold up to the temperatures so I will
have to face it in all areas of the kiln with fire brick. This won't be a problem in most areas
because the height of the mixture allows it to be covered by one layer of brick. In the firebox
the drop-off is 40 cm. or so meaning I will have to stack a number of bricks to get a fireproof
facing. With that being the case I might as well just build the arch support out of firebrick.
One of the things I have had to change in the design is putting in side buttressing. I planned
on not having to use any buttressing but talking to different people that have built catenary
kilns has made me change my mind. As seen in the picture below as the levels descend the
kiln is cut out of the dirt. I had assumed these dirt sides would support the side expansion
enough to obviate the need for side buttressing. I broke my finger lowering a 50 kilo stone into
place during the construction of my last kiln and that is one of the reasons I don't want to have
to use that method. I didn't realize my finger was broken for about 10 days. Painful memory.
on not having to use any buttressing but talking to different people that have built catenary
kilns has made me change my mind. As seen in the picture below as the levels descend the
kiln is cut out of the dirt. I had assumed these dirt sides would support the side expansion
enough to obviate the need for side buttressing. I broke my finger lowering a 50 kilo stone into
place during the construction of my last kiln and that is one of the reasons I don't want to have
to use that method. I didn't realize my finger was broken for about 10 days. Painful memory.
The area closer to the firebox has less need for buttressing than the top. I am considering
making a retaining type wall in the upper reaches of the kiln and filling in the area around the
kiln with dirt or a clay/concrete mixture. This would have the effect of side support and would
be stronger than usual. In the reaches visible in the picture below, where the kiln floor is
already below grade, I will just fill in the area between the arch and the natural grade. This will
allow me to make a kind of step so when I am stoking I will have easier access to the stoking
hole. As the kiln is fired the clay/concrete mixture will cure harder each time.
making a retaining type wall in the upper reaches of the kiln and filling in the area around the
kiln with dirt or a clay/concrete mixture. This would have the effect of side support and would
be stronger than usual. In the reaches visible in the picture below, where the kiln floor is
already below grade, I will just fill in the area between the arch and the natural grade. This will
allow me to make a kind of step so when I am stoking I will have easier access to the stoking
hole. As the kiln is fired the clay/concrete mixture will cure harder each time.
The retaining wall will take up less space than a rock buttress wall. There is limited space on
either side as is obvious in the picture below. In the area at the bottom of the picture will be
the "entrance" to the stoking area. A basic problem is the floor level of the stoking floor is
below the rain run off level. If I break through to make entrance easier the rain water will flow
around to the kiln. I don't like to having a stepped area to enter the stoking area. When firing
there is nothing more tiring in an extremely tiring process than having to ascend/descend
stairs in order to put wood in. I will try to come up with an alternative before I am done.
either side as is obvious in the picture below. In the area at the bottom of the picture will be
the "entrance" to the stoking area. A basic problem is the floor level of the stoking floor is
below the rain run off level. If I break through to make entrance easier the rain water will flow
around to the kiln. I don't like to having a stepped area to enter the stoking area. When firing
there is nothing more tiring in an extremely tiring process than having to ascend/descend
stairs in order to put wood in. I will try to come up with an alternative before I am done.
Although it is difficult to see in this photo the board in the foreground and just to the left of it in
the background are there to show the height of the finished arch. Draw a line from the top of
either board to the top of the other and that will be the top of the kiln. Cracks are very visible
in the sub-floor in the foreground. On both sides of this picture I have the triangular forms in
place for the slanting foundation that the arch will rest on. I haven't put brick in place to hold
the form in place. It is apparent that it isn't possible to drive steaks in through the concrete
base.
the background are there to show the height of the finished arch. Draw a line from the top of
either board to the top of the other and that will be the top of the kiln. Cracks are very visible
in the sub-floor in the foreground. On both sides of this picture I have the triangular forms in
place for the slanting foundation that the arch will rest on. I haven't put brick in place to hold
the form in place. It is apparent that it isn't possible to drive steaks in through the concrete
base.
Below it is easier to see the boards that outline the top of the kiln. It is apparent too the
narrowness of the space. I have gotten used to space confines working in Japan. I was
moving some work in my studio yesterday, bobbing and weaving to get around the various
encumbrances, thinking about that fact. I like to move in a straight line, from point to point in
my work but that isn't always possible here. I have left open both sides of the kiln since it is not
only a bother to have things in the way but dangerous too. I hope the finished kiln will have
enough room on either side to make passage an easy affair.
narrowness of the space. I have gotten used to space confines working in Japan. I was
moving some work in my studio yesterday, bobbing and weaving to get around the various
encumbrances, thinking about that fact. I like to move in a straight line, from point to point in
my work but that isn't always possible here. I have left open both sides of the kiln since it is not
only a bother to have things in the way but dangerous too. I hope the finished kiln will have
enough room on either side to make passage an easy affair.
This is a close up from the top of the method I used to put in the ramp that will hold the arch.
The ramp has to have good compressive strength. It isn't important that it has tensile strength
just compressive. The bricks are being used for spacers. The arch will consist of the same
type of bricks so I put two on each level and put the triangular board where I want the outside
of the finished form to be. In calculating the width make sure to take into account the thickness
of the plywood or what ever the forming is. In my case I put the side of the form that will be
touching the poured concrete mix at exactly 120 cm. from the form on the other side of the kiln.
The ramp has to have good compressive strength. It isn't important that it has tensile strength
just compressive. The bricks are being used for spacers. The arch will consist of the same
type of bricks so I put two on each level and put the triangular board where I want the outside
of the finished form to be. In calculating the width make sure to take into account the thickness
of the plywood or what ever the forming is. In my case I put the side of the form that will be
touching the poured concrete mix at exactly 120 cm. from the form on the other side of the kiln.
A side view of the same form. I will pour a concrete/clay mixture into the form and let it dry.
The mixture won't be able to stand high temperatures. In order that the concrete doesn't fail I
am putting in a floor. The floor material is a type of thick block made from fireclay. Each block
weighs about 20 kilos. They measure roughly 30cm by 30cm by roughly 13 cm. thick. Roughly
9 will cover each level with the remaining floor space being filled in by regular firebrick. These
blocks won't actually sit directly on the clay sub-floor. I am going to have a red brick floor that
sits on the concrete and then put the fire block on top of that.
The mixture won't be able to stand high temperatures. In order that the concrete doesn't fail I
am putting in a floor. The floor material is a type of thick block made from fireclay. Each block
weighs about 20 kilos. They measure roughly 30cm by 30cm by roughly 13 cm. thick. Roughly
9 will cover each level with the remaining floor space being filled in by regular firebrick. These
blocks won't actually sit directly on the clay sub-floor. I am going to have a red brick floor that
sits on the concrete and then put the fire block on top of that.
One of the things I found out after pouring a couple of these ramp components is it is very
difficult to get the concrete to float out to the correct height. After it is poured into the form and
troweled to the approximate height it tends to expand a couple of millimeters and ends up
above the finished form height. I didn't really bother too much about that but I tried to keep the
left ramp and right ramp roughly the same height even with this taken into account. It isn't a
watch I am building after all so small amounts of error will even out. There was another
problem with dirt falling into the concrete while I was troweling the mix.
difficult to get the concrete to float out to the correct height. After it is poured into the form and
troweled to the approximate height it tends to expand a couple of millimeters and ends up
above the finished form height. I didn't really bother too much about that but I tried to keep the
left ramp and right ramp roughly the same height even with this taken into account. It isn't a
watch I am building after all so small amounts of error will even out. There was another
problem with dirt falling into the concrete while I was troweling the mix.
There wasn't a lot I could do about the dirt falling into the mixture. I just floated it into the mix
and kept on going. There was another problem in the transitions between the levels. The
ramp form should be cut to extend out past the edge of the level in order to make a smoother
transition between the two levels. As I have it in my kiln the transitions are a little rough. I had
to pile up mix on the bottom level and smooth it into the top area, i.e., the area where the ramp
form is thinnest. Again, not a problem but it could be done better. The photo below shows a
good illustration of how the kiln isn't going to need a lot of side buttressing as it gets down
toward the firebox area.
and kept on going. There was another problem in the transitions between the levels. The
ramp form should be cut to extend out past the edge of the level in order to make a smoother
transition between the two levels. As I have it in my kiln the transitions are a little rough. I had
to pile up mix on the bottom level and smooth it into the top area, i.e., the area where the ramp
form is thinnest. Again, not a problem but it could be done better. The photo below shows a
good illustration of how the kiln isn't going to need a lot of side buttressing as it gets down
toward the firebox area.
In the picture below the side walls look very dry. The reality is the area directly to the left of
this picture is a mountain slope. The slope gathers water which is channeled to an area
directly to the right rear of this photo. Because of that the water table is extremely high. It is
probably just 30 cm, about 1 foot, below the finished floor level of the firebox. As I write this it
is the rainy season here and the ground in the photo below has turned a nice green from a
kind of moss on the left side of the picture. It is for that reason I am trying to get some distance
between the dirt and the kiln floor. The dampness will cause condensation on the inner walls
of the kiln when it is not in use which then falls onto the green clay and splits it.
this picture is a mountain slope. The slope gathers water which is channeled to an area
directly to the right rear of this photo. Because of that the water table is extremely high. It is
probably just 30 cm, about 1 foot, below the finished floor level of the firebox. As I write this it
is the rainy season here and the ground in the photo below has turned a nice green from a
kind of moss on the left side of the picture. It is for that reason I am trying to get some distance
between the dirt and the kiln floor. The dampness will cause condensation on the inner walls
of the kiln when it is not in use which then falls onto the green clay and splits it.
Although I have the forms cut for the firebox ramp portion, visible in the above and below
pictures I have decided to not pour concrete for those particular foundation pieces. The
reason being I would have to face the concrete with fire brick since the concrete won't stand
up to the temperature. If I have to face it it will use the same number of bricks as if I just built
the form out of brick so that is what I will do. There is an issue too of stability and strength.
Having such a tall form made out of the mix I am using seems to add some risk of failure either
of the mix or of the stability of the structure itself. A small risk but one amplified by the height.
pictures I have decided to not pour concrete for those particular foundation pieces. The
reason being I would have to face the concrete with fire brick since the concrete won't stand
up to the temperature. If I have to face it it will use the same number of bricks as if I just built
the form out of brick so that is what I will do. There is an issue too of stability and strength.
Having such a tall form made out of the mix I am using seems to add some risk of failure either
of the mix or of the stability of the structure itself. A small risk but one amplified by the height.
The picture below shows the line that I used to lay out the forms. I marked the middle of the
top level and bottom level as they were in reality, that is the true middle as it lay in concrete. I
then snapped a line between the two points. I then drew a red line on each level that matched
the center line. From this line I then measured out to get the correct alignment for the forms. I
did two measurements out on each level. That way the forms are true to the center line of the
kiln. I have a total width between the support for the arch of 120 cm. I therefore measured out
60 cm from each side of the red line. You must of course take into account the thickness of
the form material. In my case the plywood was about 1 cm. so I measured out 59 cm.
top level and bottom level as they were in reality, that is the true middle as it lay in concrete. I
then snapped a line between the two points. I then drew a red line on each level that matched
the center line. From this line I then measured out to get the correct alignment for the forms. I
did two measurements out on each level. That way the forms are true to the center line of the
kiln. I have a total width between the support for the arch of 120 cm. I therefore measured out
60 cm from each side of the red line. You must of course take into account the thickness of
the form material. In my case the plywood was about 1 cm. so I measured out 59 cm.
Although the picture looks nice the finished surface of the levels where I put in brick fronting
are the most split of all the levels. I have detailed that in some of the pictures above. In laying
out the center line of the kiln it is important to step back and look at the two levels you are
using as control levels. It they are unusually wide or narrow, if for some reason they make
poor control points it will be necessary to adjust the control point accordingly. I did have to
take into account the top level because it was the widest of all the levels. I moved the control
point, the point that I used for the top string point, a little so the snapped string line would line
up in what amounted to a good average for all the levels taken as a whole.
are the most split of all the levels. I have detailed that in some of the pictures above. In laying
out the center line of the kiln it is important to step back and look at the two levels you are
using as control levels. It they are unusually wide or narrow, if for some reason they make
poor control points it will be necessary to adjust the control point accordingly. I did have to
take into account the top level because it was the widest of all the levels. I moved the control
point, the point that I used for the top string point, a little so the snapped string line would line
up in what amounted to a good average for all the levels taken as a whole.
This is a good picture of what the idea is to finish the floor. It shows the triple floor, concrete
and red brick with a final thick layer of fire brick. This should be sufficient to keep moisture at
bay. I have always heard of snake kilns that have specially built systems to allow the
introduction of water during the firing. I don't know if this is just a rumor or a real feature. I
have most often heard it in reference to Koyama Fujio's kiln. Koyama is the standard bearer
for Nanban pottery. I think looking at his Nanban work it is tempting to assume he used water
to get his luscious surfaces. I am not convinced just on surface appearance. I think he used a
clay that allowed that kind of finish.
and red brick with a final thick layer of fire brick. This should be sufficient to keep moisture at
bay. I have always heard of snake kilns that have specially built systems to allow the
introduction of water during the firing. I don't know if this is just a rumor or a real feature. I
have most often heard it in reference to Koyama Fujio's kiln. Koyama is the standard bearer
for Nanban pottery. I think looking at his Nanban work it is tempting to assume he used water
to get his luscious surfaces. I am not convinced just on surface appearance. I think he used a
clay that allowed that kind of finish.
These thick large bricks are very difficult to find these days. The guy I bought them from told
me they are unavailable now unless you buy them new. They are heavy and difficult to
maneuver but when in place they provide stability and one on them covers a lot of space.
They make the work go very fast. They aren't solid in the sense of one big block of fireclay. If
you turn them over they have a section on the bottom that is hollowed out. The minimum
thickness is roughly 5 cm. thick. I haven't used them in a standing position, only as they are
pictured below. I don't think they would support weight if they were standing up as part of a
wall.
me they are unavailable now unless you buy them new. They are heavy and difficult to
maneuver but when in place they provide stability and one on them covers a lot of space.
They make the work go very fast. They aren't solid in the sense of one big block of fireclay. If
you turn them over they have a section on the bottom that is hollowed out. The minimum
thickness is roughly 5 cm. thick. I haven't used them in a standing position, only as they are
pictured below. I don't think they would support weight if they were standing up as part of a
wall.
This shows how I plan on guarding the sub-floor from the high temperatures the hot faces will
come under. The red brick is not able to stand up to the high temperatures but with the
thickness of the fire brick on top not much heat will penetrate down to the level of the red
brick. The only problem I can foresee is that since the red brick is used it isn't all the same
thickness which will make it difficult to get an even surface to place the large flooring bricks on.
I will probably "float" them all to the same height by using a clay/concrete mix. The proportions
will be a little different than the floor mix, maybe clay 5 to concrete 1.
come under. The red brick is not able to stand up to the high temperatures but with the
thickness of the fire brick on top not much heat will penetrate down to the level of the red
brick. The only problem I can foresee is that since the red brick is used it isn't all the same
thickness which will make it difficult to get an even surface to place the large flooring bricks on.
I will probably "float" them all to the same height by using a clay/concrete mix. The proportions
will be a little different than the floor mix, maybe clay 5 to concrete 1.
The thickness of the concrete mix is much thicker than the photo below suggests. The leading
edge is thin on some levels, thick on other levels. I used the same board to level the forms out
on all the levels. I put the board on the elevation stake I had driven after excavating the level.
The board was the thickness I wanted the concrete to be. I then put a level on the board and
set the front form. This method made sure the entire level was the same thickness as the
control board. The leading edge looks different on each level depending on how well the
leading edge form board held the dirt in. Sometimes it let dirt slip through, giving a thin edge.
edge is thin on some levels, thick on other levels. I used the same board to level the forms out
on all the levels. I put the board on the elevation stake I had driven after excavating the level.
The board was the thickness I wanted the concrete to be. I then put a level on the board and
set the front form. This method made sure the entire level was the same thickness as the
control board. The leading edge looks different on each level depending on how well the
leading edge form board held the dirt in. Sometimes it let dirt slip through, giving a thin edge.
The picture below shows how I cleaned up the step areas of the kiln. I had a problem with the
edge of the step being exposed and the dirt being gradually undermined. I tried brick but that
wasn't good. I ended up putting a trowel full of concrete mix there and trying to pack it in as
best as I could. The picture also shows a transition area of the arch ramp. I have already
placed the mix and removed the forms. The ramp has set up. The transition from the upper
level to the lower level is smooth enough for my requirements. I will have a thin layer of mortar
between the mix and the first arch brick so it isn't necessary to have a completely smooth
finish.
edge of the step being exposed and the dirt being gradually undermined. I tried brick but that
wasn't good. I ended up putting a trowel full of concrete mix there and trying to pack it in as
best as I could. The picture also shows a transition area of the arch ramp. I have already
placed the mix and removed the forms. The ramp has set up. The transition from the upper
level to the lower level is smooth enough for my requirements. I will have a thin layer of mortar
between the mix and the first arch brick so it isn't necessary to have a completely smooth
finish.
This shows the forms for the bottom ramp as I was preparing them. This is the left as the kiln is
faced. I have only driven one long stake. There is a problem that isn't apparent in this picture.
If you stretched a string from the top of the kiln to the bottom of the kiln at the level of the arch
ramp, in a perfect world you should have a consistent grade. The ramp should not have any
sudden drops or bumps. In the area pictured below there is a sudden change of grade. This is
caused by having a distance of 100 cm. that has a vertical lift of 40 cm between it and the
next level. The standard for the kiln is 100 cm. with a vertical of 14 cm.
faced. I have only driven one long stake. There is a problem that isn't apparent in this picture.
If you stretched a string from the top of the kiln to the bottom of the kiln at the level of the arch
ramp, in a perfect world you should have a consistent grade. The ramp should not have any
sudden drops or bumps. In the area pictured below there is a sudden change of grade. This is
caused by having a distance of 100 cm. that has a vertical lift of 40 cm between it and the
next level. The standard for the kiln is 100 cm. with a vertical of 14 cm.
grade. To elaborate, the grade change is caused by a sudden change in the angle of the I will
take care of the grade change by extending the wall of the arch support up to meet supporting
ramp. The change in grade could be remedied by extending the ramp out so the grade is
maintained. The effect of that would be to lengthen the kiln. I don't want a longer kiln so
instead of having a smooth end to the arch ramp as is suggested by the picture below I will
have an ending that is actually a little higher, like a step. By raising the ending point of the
ramp I will in effect lessen the slope of the ramp.
take care of the grade change by extending the wall of the arch support up to meet supporting
ramp. The change in grade could be remedied by extending the ramp out so the grade is
maintained. The effect of that would be to lengthen the kiln. I don't want a longer kiln so
instead of having a smooth end to the arch ramp as is suggested by the picture below I will
have an ending that is actually a little higher, like a step. By raising the ending point of the
ramp I will in effect lessen the slope of the ramp.
The kiln floor at this point is roughly 1 meter below the natural grade. This depth will help in
buttressing the walls after I have the arch in. I designed a catenary arch for the express
purpose of not having to have buttressing but it looks like I will have to. I thought about just
lopping off the top of the arch to make the kiln size a little more manageable but that would
seem to require a total redesign of the arch ramp. I am going to end up with a kiln that is a
little larger than I planned and one that requires buttress walls. I will build the buttress
retaining walls out of red brick and fill in the area with clay-heavy dirt.
buttressing the walls after I have the arch in. I designed a catenary arch for the express
purpose of not having to have buttressing but it looks like I will have to. I thought about just
lopping off the top of the arch to make the kiln size a little more manageable but that would
seem to require a total redesign of the arch ramp. I am going to end up with a kiln that is a
little larger than I planned and one that requires buttress walls. I will build the buttress
retaining walls out of red brick and fill in the area with clay-heavy dirt.
This picture is a good overview of the progress of the arch ramp and using the red brick as a
form holder. On the right side of the photo the ramp is completed down to the fourth level, on
the left side to the third level. It isn't necessary to pour the whole ramp at the same time.
Usually with concrete it is desirable to complete any pours as a single unit because the join
think the strength will be affected by have incremental pours. My mixer is large enough to mix
enough to pour the ramp section for three and a half levels on one side.
form holder. On the right side of the photo the ramp is completed down to the fourth level, on
the left side to the third level. It isn't necessary to pour the whole ramp at the same time.
Usually with concrete it is desirable to complete any pours as a single unit because the join
think the strength will be affected by have incremental pours. My mixer is large enough to mix
enough to pour the ramp section for three and a half levels on one side.
I won't be able to install the floor until after I put the arch in. The height of the floor will be taller
than the arch at the corners so it would be impossible to get a proper fit in either the arch or
the corners of the floor. I will put it in after removing the arch form. This way will work out a little
better than if I had put it in already. I have decided to use only the smallest fragments of brick
in the sub-floor. If I had gone and put it in I would have used the bricks I have in place that
were holding the arch ramp forms in place. They are a mixture of full length, half length and
smaller. Since I have to build a wall around the kiln I will use all the big bricks for that.
than the arch at the corners so it would be impossible to get a proper fit in either the arch or
the corners of the floor. I will put it in after removing the arch form. This way will work out a little
better than if I had put it in already. I have decided to use only the smallest fragments of brick
in the sub-floor. If I had gone and put it in I would have used the bricks I have in place that
were holding the arch ramp forms in place. They are a mixture of full length, half length and
smaller. Since I have to build a wall around the kiln I will use all the big bricks for that.
This picture shows the use of bricks as spacers in setting up the form. This is the size of bricks
I will use in the arch so I used the same for making sure the ramp would be the proper size.
The next step in building the kiln from this picture is to mix up some material and place it into
the form. I started from the middle part of the form and got a good amount of mix in place
before removing the bricks. I then went and put the mix into the areas where the bricks had
been. Only in the area where the ramp is most shallow did I have a problem leveling out the
mix. I just removed a red brick or two to make room for the trowel.
I will use in the arch so I used the same for making sure the ramp would be the proper size.
The next step in building the kiln from this picture is to mix up some material and place it into
the form. I started from the middle part of the form and got a good amount of mix in place
before removing the bricks. I then went and put the mix into the areas where the bricks had
been. Only in the area where the ramp is most shallow did I have a problem leveling out the
mix. I just removed a red brick or two to make room for the trowel.
This photo shows the arch ramp completed for a couple of the levels. I have put bricks on the
transition points of several of the levels. The points are where the upper level transitions to
the level below it. They are important because it is the easiest area to get a bump in the grade
line. I took extra care to make sure there was a continuation of the grade in these areas. In the
picture, on the right side it is possible to see a couple of trowel marks. I am not concerned
about small marks like that as I am going to lay the first layer of bricks on a layer of mortar that
will have the effect of leveling out small imperfections.
transition points of several of the levels. The points are where the upper level transitions to
the level below it. They are important because it is the easiest area to get a bump in the grade
line. I took extra care to make sure there was a continuation of the grade in these areas. In the
picture, on the right side it is possible to see a couple of trowel marks. I am not concerned
about small marks like that as I am going to lay the first layer of bricks on a layer of mortar that
will have the effect of leveling out small imperfections.
This brick is right on the thinnest part of the ramp, the transition between one level and the
next. I took particular care in this area to get the transition smooth. If I were to re-do the
"engineering" of this detail I might dig out some of the sub-surface dirt at the thinnest point in
order to get a thicker concrete mix here. I don't think the thinness of this point will be a
problem but I would still like some over engineering here. This photo is also at the point where
the arch starts to descend into the natural sub-grade. From this point to the front of the kiln all
the arch will be partially underground.
next. I took particular care in this area to get the transition smooth. If I were to re-do the
"engineering" of this detail I might dig out some of the sub-surface dirt at the thinnest point in
order to get a thicker concrete mix here. I don't think the thinness of this point will be a
problem but I would still like some over engineering here. This photo is also at the point where
the arch starts to descend into the natural sub-grade. From this point to the front of the kiln all
the arch will be partially underground.
This shows a part of the ramp that is a little wider than usual. As I proceeded down the length
of the kiln I got "better" at getting the forms in place and things gradually got a little wider. I
don't recommend having the ramp too wide for a number of reasons. One it wastes materials.
Not a major reason but one reason. The wider the ramp is the more surface the bricks have
the level down to the lowest brick and by having a wider base it is more work to make sure the
buttressing material is sufficiently packed in to minimize movement.
of the kiln I got "better" at getting the forms in place and things gradually got a little wider. I
don't recommend having the ramp too wide for a number of reasons. One it wastes materials.
Not a major reason but one reason. The wider the ramp is the more surface the bricks have
the level down to the lowest brick and by having a wider base it is more work to make sure the
buttressing material is sufficiently packed in to minimize movement.