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raku kilns and burners

updated wed 17 oct 07


Steven Branfman on tue 16 oct 07


The recent thread that began with Otto's question about not being able to=20
reach temperature in his raku kiln was entertaining but ultimately caused me=
overfire. "you're burner port is too small, the exhaust is to small (exhaust=
a kiln? you mean flue?), the shelf is too tight to the wall, move the burner=
further away, move it closer, install a regulator, get a fan....on and on. A=
advice well intentioned and all of it possible solutions to specific=20

I suspect that the flood of help was heartwarming to Otto but likely left hi=
with more questions than answers. Of course he may have taken all the advice=
and rolled it into his kiln which now looks like a cross between an=20
Appalachian still and some Rube Goldberg contraption. So who am I to step in=
and add my=20
two cents to the equation? Just a knowledgeable observer who all too often=20
witnesses people wanting to help but ultimately making the situation even mo=
confusing than before. I don't know, maybe I'm becoming a curmudgeon with li=
patience for inaccurate or irrelevant information no matter how well=20
intentioned it may be. Perhaps Otto has solved his problem. Perhaps not. Reg=
ardless, I=20
would like to offer some advice on the topic.

If your kiln is not reaching temperature the problem is either that the=20
combustion system is underpowered or there is not enough air for efficient a=
complete combustion. From my experience it is usually the latter and thankfu=
all of the responses to Otto's question did recognize that in one form or=20
another. Without going back into all of the details of his kiln, my advice i=
s in=20
this case to focus directly on the combustion system and I was surprised tha=
there was universal acceptance of the weed burner as acceptable and reliable=
. A=20
weed burner is designed to burn weeds, melt snow, work with tar, and do othe=
pyromaniacal things around your house. They are not designed for firing kiln=
I know, the wooden spoon I use is not designed as a throwing stick. The meat=
tenderizer is not designed to texture clay. The cheese slicer is not designe=
to facet your cup. Enough said. I've fired many raku kilns successfully with=
weed burners. In fact I just came from doing a workshop at Brackers Good Ear=
Clays where we had 20 people using 4 kilns all powered with weed burners wit=
not a single broken pot, underfired kiln, or piece not fired the way we=20
intended it to be fired. Why the success? Because the Bracker Raku Kiln is a=
of genius; a carefully considered, simple, no frills kiln that is expertly=20
designed to take advantage of the simplicity of the supplied weed burner. Th=
limited control of the weed burner is compensated for by the design of the k=
It is virtually foolproof and THE perfect kiln for someone new to raku with=20
limited firing experience. However, the key phrase here is =E2=80=9Climited=20=
control=E2=80=9D. As=20
a stock item, the weed burner ihas only a valve that adjusts gas flow and=20
many weed burners I=E2=80=99ve seen lack even that. Yes you can add a blower=
, you can=20
install a regulator (what pressure do you set it at??), you can even work ou=
some kind of primary air control. Why try to make a Lexus out of a Corolla?=20=
combustion system is the heart of your kiln. It is where control begins and=20
reverts back to. Someone said that you don't have to go to Ward. Maybe not i=
your kiln is matched to your weed burner combustion system and you are conte=
with the restricted control that it offers.

A fully adjustable gas fueled combustion system is designed to work under a=20
fixed gas pressure set by either a fixed or adjustable regulator. Gas flow i=
adjusted by a valve between the regulator and burner. Primary air flow is=20
controlled by either a passive system (venturi for example) or an electric b=
With a well designed and fully adjustable combustion system you have the=20
ability to do things that the weed burner won=E2=80=99t allow. You can easil=
y manipulate=20
the atmosphere. You can adjust a chamber that is heating unevenly. You can=20
compensate for a drop in gas pressure or a shift in wind direction. Mark War=
d will=20
be the first to tell you that you don=E2=80=99t have to go to him for a comb=
system but go to someone who is knowledgeable and reliable. The Brackers wil=
tell you if their kiln is for your and will be the first to tell you that th=
kiln is not for everyone. And me? Why through this whole diatribe not once d=
I mention this raku book that some guy named Branfman wrote.

Go ahead, I dare you, have fun with raku.

Steven Branfman

Steven Branfman
43 Chinian Path
Newton, MA 02459 USA
H: 617/964 0442
C: 617/447 3500
W: 781 4497687

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