mel jacobson on sat 29 may 99
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i do not presume to bother those of you that have read
this in cm......but, have had a dozen requests for this,
from people that missed it. and craig martell is a very'
\smart guy.
SALT/CERAMIC FIBER AND ITC
Mel Jacobson
One of the most destructive forces in firing is salt. It melts bricks,
collapses arches, destroys flues and ports and is generally a killer of kilns.
During a long conversation at the 1998 NCECA conference on the
destructive forces of salt on kilns, Feriz Delkic` owner of International
Technical Ceramics in Ponte Vedra, Florida said to me "I think my products
will resist the effects of salt corrosion in a kiln". I was very skeptical,
in fact told him "I doubt that very much". After several days of discussion
he came up with the idea of building a kiln at my farm in Wisconsin and
testing the effects of salt using his modules and thermal coatings.
I felt that the only fair test would entail the sharing of expenses so I
was not obliged to give answers that were not proven. He agreed and said
He would supply several small modules, some ITC spray materials and some
scrap ceramic fiber. I would supply a variety of brick, steel support, shelves
and posts, a new stack with thermal liners and a shelter to house the kiln.
Feriz "asked" for design rights, and I agreed as long as we used the
Nils Lou double venturi down draft system and propane burners, and that
Kurt Wild, potter and long time friend would be brought into the project.
Without question the 15 quality potters at our summer adult art camp would
witness, fire the kiln and evaluate the results. I think we "shared" the
design rights.
Originally we wanted a kiln that would be a changeable, updraft/
downdraft combined in one kiln. That became a multiple venting nightmare for us
and was disregarded. The idea still has merit, as an updraft kiln will
generally fire faster than a downdraft, but speed was not our most pressing
issue.
One of Feriz' most emphatic requests was based on the theory that a kiln must
breathe air on all sides, in other words, "do not build it on a solid concrete
or block base".
This became a challenge to us and the final solution was to build a loose
concrete block base and place expanded metal on top of the block, leveled
with 1/8-inch steel strap. The hard brick base leveled very well on this
system. We sandwiched a course of soft brick between two layers of hard
brick. The expanded metal allowed air to circulate under the kiln.
We proceeded to build a standard flat top kiln, 36 inches square and 34
inches high, inside dimension, and a doorway for potential bricking of 9 inches
by 27 inches by 34 inches. A total of nearly 32 cubic feet. This size is in
keeping with other kilns that Kurt and I have been building, small, compact and
easy to fire, with very fast turn around time. We used several hundred
used soft brick from Thermal Ceramics and purchased K2300 and K2600 soft
brick from A.P. Greene. Kurt wanted to use a variety of brick inside the
kiln so that we could measure which variety did or did not fail. The shelves
were eight 14x16 inch silicon carbide and four 4 x16 inch silicon carbide. The
roof module was 56 inches square, made of ceramic fiber re-folded on itself to
10 inches thick, re-rod support and wired together. The module was very wet
when delivered, and with spring storms it did not dry. It was another
challenge to put it in place because of the water weight. We finally just
"picked it up" one day using six strong people, with one person under the
module for support. It just popped above our heads and we walked it in
place and set it down. A 1/4 inch 4X6 inch angle iron frame was placed
around the kiln with angle iron supports. A similar frame was built for the
door module, it was hinged to the frame with an added cast iron wheel on
the lower outside corner to take the weight and facilitate the opening
and closing of the door.
ITC 100 H.T. coating was applied to all inner surfaces of the kiln, using a
sandblaster gun with about 60 pounds of constant pressure. I was advised
by Feriz to give extra heavy coatings to the modules. We followed the
normal procedure of cleaning and wetting all surfaces. It was decided that
the back wall of the kiln was to be laminated. We used one-inch fiber
blanket soaked in ITC 100 H.T. and pounded lightly into the already wet wall of
brick, soaked with ITC100 H.T. It was a very easy process and it worked well.
Only the hot faces of the modules were sprayed.
We took care to spray the entire length of the stack riser sleeves with
ITC100 H.T. The stack was built of two lengths of 24 gauge, galvanized 10-inch
pipe, five feet long, screwed together with sheet metal screws. The risers
were from Fire Brick Supply of St. Paul, MN. The completed stack was placed
on the standard flat top flue-box with its double venturi. "Trowel-eze", one
of our favorite mortars, was used to assemble the flue-box.
The kiln was fired empty to about 2000 degrees F. to dry the spray
materials and set it against the brick and modules. I then sprayed the kiln
inside with a second coat of ITC100 H.T. with heavy applications to
the lamination and modules. I used at least 5 coats on the fiber
surfaces. After the initial glaze firing of the kiln, I sprayed the entire
kiln with an even coating of ITC296A, top coat. All kiln shelves and posts
were sprayed with ITC100 H.T.
The first salt firing was amazingly fast; we used our Nils Lou propane
burners with about 18 pounds of pressure. A 25 foot copper line from
the 500-gallon tank and 20 feet of high pressure rubber hose from the connector
to the burners was used. We reached reduction temperature of 1800 degrees F.
within two hours from a dead start, and cone nine was down in four hours. We
began salting with
about 15 pounds of salt and completed it in less than an hour. Cone 11 was
flat over. We cracked the door the next morning at 6 a.m., and the results
were wonderful, perfect light salt and not a reject pot in the entire kiln.
We unloaded at 8 a.m., and started to load again at 10 a.m. and lit the
kiln at 11:30 a.m. The kiln again fired in less than five hours. We
continued this schedule for six straight days.
On the fourth firing we noticed some melting of brick in the flame way
wall. I decided to make a patch in the area with ITC 200 EZ fill material and
ITC100 H.T., laminating a 4-inch by 12-inch piece of rigid 1/4-inch fiber
soaked
with ITC100 H. T. This hot spot did not re-occur during the final two firings
and the patch held perfectly.
The fourth, fifth and sixth firings we almost identical, with heavy salt
applications on the pots. We where more than pleased with the results. There
were no reject pots from the hundreds that we fired. The kiln
fired to near perfection, in record time, with an amazing 50 % savings in
fuel. Our old salt kiln fired in about 7 hours, with
the same burners and pressure, and was about 40% smaller. Our old soft
brick salt kiln started to deteriorate badly on the first firing 6 years
ago, and was unusable after only 30 firings. The inner layer of bricks had
mostly melted with some brick turning to dust. The old kiln was built
entirely of new K2500 bricks from Thermal Ceramics.
During the new kiln firings we threw a salt mix using three fourths rock and a
quarter table. We wanted to fire very hot and not be timid at any time with
this kiln. Kurt and I insisted on firing fast, wide open, and a heavy salt
application. The kiln held up amazingly well, in fact, far beyond what we
expected.
Here are the results: There was no damage to the modules or the lamination.
Some small melting at the fire port walls that were later bandaged; one salt
port has some brick melting on the lower edge, and we lost the face of one
brick in the door way section. The kiln shelves did not gather salt where
they were sprayed with ITC100 H.T. Smart pills just fell off the
shelves. The shelves did not need cleaning between firings; no posts
stuck to shelves.
ITC products are not magic, or are they intended to be. Feriz Delkic` has
created quality products that if used correctly and as he instructs, will
work in any kiln. We know that time will be the most important element in
this test. Six firings gave us a great deal of information, but 60 more
firings will give us the final answer. I am sure that heavy salting will
ultimately break down this kiln, but the ITC products have slowed this
process considerably.
I have now sprayed ITC thermal coatings on 6 kilns that I own, including a
small electric kiln that is 35 years old. In all cases I have had a fuel
saving,
faster firings, and better pots. None of the coatings have spalled off the
kilns. ITC 100 H.T. stabilizes the surface of fiber and does not allow the
small fragments to be air born. This technique alone makes fiber kilns
stronger and safer to use.
Without question we have built a very good kiln. It is not a bargain kiln,
in fact it was expensive, but well worth the time, effort and expense. Kurt
and I feel that this kiln will serve us well for many years to come.
Materials and costs.
The kiln used nearly 800 bricks
Floor: three courses, 2 hard one soft, 216 bricks
Three walls: 14 courses times 34, 475 bricks. 4 types of IFB.
Flue-box: 96 brick, all hard, fire brick.
We estimate used IFB's at one dollar each.
New IFB's about four dollars each. Three cases @24 $290.00
Hard brick are worth about fifty cents each. $218.00
IFB's. $475.00
Riser sleeves, $83.00
Galvanized stove pipe, $30.00
Shelves, used. $400.00
Posts, new and used $150.00
Metal and welding, $300.00 (we did our own)
Modules $1,000 each,/ $2,000 @$100.00 per square foot, plus shipping.
ITC spray @ $150.00 per gallon, $450.00
Pole building: $1200.00. (includes slab)
Mel Jacobson/ Minnetonka, MN
List of camp potters:
Bob Anderson
Reg Behrens
Kerry Brooks
Kevin Caufield
Bob Fritz
Doug Gray
Bob Holman
Susan Karrasch
Andy Kazukewicz
Larron Lerdall
Dawn Makarios
Dannon Rhudy
Colleen Riley
Tara Simpson
Kurt Wild
S
http://www.pclink.com/melpots
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