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fastfire kiln question

updated thu 9 sep 99


David Hendley on wed 8 sep 99

This is an answer to a specific question from Deborah
Bouchette. In case anyone else is interested:

Q: I've designed the Olsen fast-fire on paper now with a double wall of
Where one uses 18x18x1 kiln shelves to make a floor over the fireboxes, what
does one use to make up that 1" of height on the rest of the walls and
to keep the courses even?

A: What I do is cut a notch out of the insulating bricks,
as needed. The first course of bricks above the fireboxes
will sit partly on the kiln shelves and partly not, because
the kiln shelves do not go all the way to the outside wall.
Just cut a 1" deep piece out where the bricks sit on the kiln
shelves. It's easy to cut insulating bricks with a hand saw
(it will ruin the saw, though!). If available, I use 3" thick
bricks for this course, rather than the U.S. standard 2 1/2"
thick bricks. This leaves more material after the 1" piece is
cut out.
I used 12 X 24 kiln shelves for the kiln floor/firebox roof.
You don't have to use 18 X 18's.

David Hendley
Maydelle, Texas

----- Original Message -----
From: Deborah Bouchette
Sent: Tuesday, September 07, 1999 12:34 PM
Subject: FW: Olsen's Fastfire Wood

----------------------------Original message----------------------------
Thank you, David; I have both Olsen's and Lou's books, and found some of
answers, but not all (angle iron instead of channel, Kaowool, no steel
those are all great answers). Nils' book is rather rambling and a bit of an
advertisement (plus focuses on gas); Olsen's is very historical (after all,
would he disclose how to completely build a kiln when he sells kits?).
is out-of-print, and although I've found it on, I've not yet
ordered it.

I also have Leach's book with its rules-of-thumb from and engineer and a
Japanese potter. Very interesting to read Olsen's rules and Nils' rebuttal
then read Leach.

I've designed the Olsen fast-fire on paper now with a double wall of bricks.
Where one uses 18x18x1 kiln shelves to make a floor over the fireboxes, what
does one use to make up that 1" of height on the rest of the walls and
to keep the courses even? The only thing I could come up with (short of
"ripping" a lot of bricks) is using a castable refractory and making
several custom-sized 1" thick shelves. In Casson's book, his itty bitty
kiln plans have the same flaw. Plus my using a double wall of bricks
complicates things because kiln shelves just don't come that wide. I'm
on modifying the design to use a catenary arch (yes, I know, they are harder
load and don't fire as evenly).

I'm also sending away for the June 1996 Ceramics Monthly, which purportedly
a design for a Bourry box. Someone made a comment that a Bourry box takes
larger pieces of wood and therefore doesn't have to be stoked quite as
boon, since I will be firing alone most of the time. I haven't looked on
bookfinder for Bourry's book yet. And I'll be writing to Steve Harrison
regarding his no-bull-igama.

I expect I will put in some good footings, since we are on clay loam that
very wet in the winter and we get wiggly earthquakes every couple of years.

Again, thanks.


now 15 years in Oregon
Deborah Bouchette

-----Original Message-----
From: David Hendley []
Sent: Thursday, September 02, 1999 9:08 AM
Subject: Re: Olsen's Fastfire Wood

----------------------------Original message----------------------------
Deborah, most of your questions are just general
kiln-building questions, not specific to the fast-fire.
Buy or borrow some kiln building books before you start.
The 3 best books are Olsen's, Nils Lou's, and Daniel
Rhodes'. Look over all 3 if you can.
To answer your specific questions:

Where, in general, do I go to get the channel steel for the frame?

It's all angle iron. 2" angle iron is good - that means each
side is 2" wide. Get it at the junk yard, a welding shop,
or a machine shop. Angle iron is very common. You don't
need to specify any load carrying capacity or anything - just
ask for 2" angle iron.

Do I interlock the double rows of brick in the wall,

Yes, usually every 4 rows or so.

If I double the walls, then is it common sense to double the door as


How do I handle the junction between the walls and the flue?

You need to bridge over the opening to the flue.
This can be done with a cobble-arch, or you can
buy some special longer bricks to help bridge the

How do I double-up the roof? Just row over row?

Most people build the roof with arch bricks, which will give you
a 4 1/2" thick roof, and then add layer or two of ceramic
fiber (Kaowool) over the arch to add more insulation.

How much wear and tear does it save by putting a shed roof over it?

A shed roof is an absolute necessity for a kiln built
with insulating bricks. You have invested too much in the
bricks to cheap-out by not building a good shed.

Should I consider predominant wind direction in siting the kiln?

Yes. It will create smoke. You don't want it blowing
in your door or over to your close-by neighbors.

How big should cement footings be to hold up that mass?

It's not much weight, compared to a building.
In Texas, you don't even need a footing, just a slab.
in colder climes, I think you would want to go with

Does anyone put steel mesh over the chimney top, or does that cut draft?

Steel mesh would not last through the first firing.
It's HOT up there. I've never had a problem with
hot flying embers from the chimney.

If you've built houses, you can certainly build a kiln.
If you can't weld, just get someone to do the welding
for you. No big deal. Won't cost much.

David Hendley
Maydelle, Texas