Kiln Deterioration
&
Structure Failure |
After hundreds of Kiln Firings,
Robert has documented the many instances of
brick and shelf failure |
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Silicon Carbide
Erosion
The sodium used in this salt kiln ate away the silicon carbide Kiln Shelf, causing the whole stack to shift.
The shelf was located under a salting port, and the salt
packets landed directly on the shelf, instead of in the firebox as intended.
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You can see, in the lower far right corner, the shelf literally vaporized
and the shelf post has fallen away. The pots, upper right, help support the shelf
for the lost post. |
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As bad as the photo looks only a half dozen
pieces were lost. |
IFB - Fire Brick Failure
Insulating Fire Bricks
Over-fired |
This brick was rated at 2000F but was
fired to 2400F and fired in a salt atmosphere. |
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The brick on the left was identical to the brick
standing to its right. After one firing in the door of Roberts Salt
Chamber the brick compressed by one third.
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Another view of the same two bricks. |
Kiln Post Fatigue
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Kiln Post Fatigue
Gas firing kiln post failure. A hi-heat brick , that was 4" tall compressed
3/4 of an inch. See second post from bottom shelf.The hi-heat firebrick
had been in over 200 firings
when it
suddenly fatigued under the load of shelves. |
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Kiln Shelf Failure
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Kiln Shelf Failure
This fireclay (high alumina) shelf held up well for
Six Wood/Salt Firings, but warped extensively in the Seventh FiringThe shelves on
the lower levels failed the most severely. |
Brick Deterioration
Brick
Deterioration |
Wood Firing
and
Salt Glazing |
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The low alumina content of the firebricks bricks
used to build this kiln has resulted in general brick failure in the connecting flue areas.
The kiln has been fired 60 times and has experienced heavy
wear from the large amounts of salt used in the second chamber (at right).
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These photos are of the
Noborigama 60 cf
built in 1991. The
wear shots are after being
used for 13 years. The back wall was constructed of Insulating Fire Brick (I.F.B.),
for their superior insulation. The trade off in using I.F.B. brick, is a shortened life, as seen by
the extensive melting in the left rear. |
Wear of Refractory Materials
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Wood and Salt Wear
on the
Kiln's
Refractory Materials.
Quality of Bricks
The ceiling bricks in the salt chambers are of two different
compositions. The wider arch bricks have a higher Silica Content and
have glassed over earlier, than other "higher alumina" bricks. This photo
was taken after four salt firings, and the walls and arch are already well
coated. |
Wear of Refractory Materials
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Quality of Bricks
The arch bricks in the salt chamber exit flue are composed
of 85% Alumina. They resist glazing due to their low silica content.
Most bricks used in a salt kiln are rated as "super duty" which is
roughly equivalent to 42% Alumina. The High Heat Bricks used by most
potters to build kilns are rated at 34% Alumina. |
Quality of Bricks
The arch bricks over this Entrance flue
(located in the salt chamber firebox) are composed of 85% Alumina,
which resists making a glaze. The bricks above the arch are of a lower
alumina content, and as can be seen above, are so meted they flow
as a liquid.The Firebox of the salt chamber is the most heavily
impacted area since this is where the "salt burritos" are introduced to
the kiln. |
05/14/13
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