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salt kiln advice needed!

updated fri 24 oct 97


Nan Rothwell on thu 9 oct 97

I need kiln-building advice. My old and faithful salt kiln died during a
firing on Monday, when the bricks on the walls near the burner ports, which
had been cracked and spalling for some years, suddenly began to slough off,
blocking the ports. It was more than a little unnerving, since I couldn't
decide whether to keep firing and hope to salvage the pots or shut down for
safety reasons. (In the end, I got much of the kiln to the low range of an
acceptable temperature) But the kiln, which was old and ailing, is
definitely dead. Because I'd been hoping to nurse it along through the fall
and dismantle it at relative leisure during the post-Christmas lull, I hadn't
made any clear decisions about my next kiln. Now that I am facing a MUCH
quicker turn-around, I am appealing to the kiln gurus among the ClayArt group
for some advice.

First question: I am thinking of using soft bricks (Thermal Ceramics K-23's)
on the interior with ITC100 coating. (I've used those IFB's in my door over
a number of salt firings and they held up reasonably well... And I would
love to avoid having to heat up all that hard brick.) Does anyone know how
the small salt kiln Nils Lou described in the last issue of "Clay Times" is
holding up? As of the article, it had survived 35 firings... (Nils? Are you
reading this?) Does anyone know any definitive reason I should avoid that
combination (of IFB and ITC) for a salt kiln?

Second question: Both of my salt kilns have been propane-fired downdrafts,
with burners coming in from the sides (the walls that support the arch),
hitting bagwalls, and with flames exiting from a central exit flue to a back
chimney. In both kilns, I created an extra-large channel in front of the
burners, so that I could throw in the salt plus some wood. And in both
kilns, that's been the area that deteriorated most badly. So my question
is, how about creating an exterior firebox? (My logic is that if that's the
area that goes first, how about isolating it from the main body of the kiln,
so that I could replace just it, and not the whole thing, when it goes...) I
know that propane has a relatively short flame. Would I be losing the most
important heat by making the propane travel through a short firebox first?
Does anyone have specific advice/ideas about a design for such an exterior
firebox area? ( In the same issue of "Clay Times," Mel Jacobsen describes a
wood/salt kiln. But reading it, I wasn't sure if the burners went through
the firebox area or directly into the kiln...)

Third and final question: I'll probably stick with the basic size of my
current kiln (front and back tiers of two 14"x22" shelves) If I go with an
external firebox, though, I won't need as much space within the kiln behind
the bagwalls. So I am looking for opinions on what is a good distance to
leave around stacks of shelves?


Nan Rothwell
221 Pottery Lane
Faber, Virginia 22938

Louis Katz on fri 10 oct 97

If you were to build a =22traditional=22 70's style salt kiln with burners
on the side facing the bagwalls in a downdraft, I would suggest
mounting the burners higher in the wall, This seems to help keep the
floor and bottom of the kiln behind the bagwall cooler. I think you
will pay a real price in fuel for building an external firebox.