William Brouillard on fri 23 aug 96
Salt kiln stack construction.
The height and interior cross sectional area of the stack will be determined
by at least three things.
1. The type of burner system you are using. Forced air systems require
less in terms of height than do natural draft systems. Natural draft systems
depend on stack height to develop velocity in the draft.
2. Local building, zoning or fire codes which may specify certain types
of construct or construction materials. You should check with your local
codes or Fire Marshall. It may be that your stack has to extend a certain
height above your roof line or that it can not be loose brick construction
and must be mortared.
3. Salt firing is a vapor process that is usually done at high temperature.
The exhaust gases will be very hot and very corrosive. That may eliminate
some materials that could be used on other types of kilns. Chimney liners
and red brick are probable out of the question.
A ten foot stack with a 9" x 9" flue area would use approx. 300 standard
Any low duty firebrick should do the job. Scrap brick could be used in
the upper third of the stack where the heat and corrosive effects of the
vapor will be less..
Many potter lay the brick for the stack dry or with a 50/50 mix of fireclay
and sand. It fills the gaps but comes off easily when rebuilding.
The base of the stack should be two courses thick if laid dry. It will be
more stable and provide a better heat differential for the stack. I usually
put insulation brick as the outside layer to protect students from being
burned on the hot firebrick and to increase the heat differential which
increases the velocity of the flue gasses. A frame of angle iron will hold
the loose bricks in place and provide stability for the stack.
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