Nils Lou on wed 21 oct 98
For Gavin Stairs, Janet Walker, Gary Wang, Linda Blossom and others who
are interested I submit the following. ITC coatings are not like anything
else. They start as coatings, but then the magic begins.
This is long, but I would like to share my anecdotal experiences
with the electric/reduction process and with ITC213, the ceramic coating
specially made for metals. There is much misinformation, conjecture and
interest in electric/reduction and element degradation.
I have described, in the new edition of The Art of Firing, AC
Black, the experimental electric/reduction test kiln, (AIM) in which I
have fired numerous (100+) reduction tests using the elements to get
temperature and gas to modify the atmosphere to reduction levels of .65 on
an OXYprobe. The gas (LPG) is introduced by simply placing a small Bunsen
burner under the kiln and valving the flame to the desired reading on the
OXYprobe. The flame is introduced at approximately 1650F. There is a small
port in the floor for the flame to enter and a small port in the lid
acting as an exit flue. I chose gas as the reduction agent because it is
significantly easier to valve that fluid than roughly estimating wood
chips or other organics. The new kiln was prepared by spraying the
interior with a thin coating of ITC100HT, firing it empty to 2000F and
spraying an additional coating of ITC296A with one more firing to 2000F. I
have not yet changed the elements, though I have a new set ready, coated
with ITC213.
It is my understanding that ITC coatings are not simple
insulators. Applying ITC coatings to surfaces is as simple as painting a
wall, but the similarity ends there. Paint on a wall is, and remains, a
coating, completely separate in nature from the wood or plaster it rests
on. The ceramic coatings from ITC, however, ultimately combine in an
irreversible matrix, forming, in essence, a new ceramic interface using
nano-phase technology where electrons are exchanged and the voids in the
parent metal (read element) are filled. When an element is heated by the
introduction of an electric current it immediately begins to degrade (in
any environment) by spitting, losing its mass and becoming spongy. With
the ITC coating this doesnt occur. The element retains its original mass
for an extended period.
For example, if you weigh a new, uncoated element (1000grams),
install, fire it ten times and re-weigh it, it may weigh only 650grams
through the action of colliding molecules and electrons. It has lost
significant mass through the spitting phenomenon. The net effect is the
element material becomes spongy and while the diameter may be nearly the
same as new, the mass has decreased with a resultant increase in
resistance and a lowering of amperage over time. This can be physically
observed in sections of an element which remain dark while other parts of
the element are glowing. If a similar element is thinly coated with ITC213
there will be no decrease in mass, no increase in resistance, no decrease
in amperage after 10
firings, after 20 firings, or 100 firings. This is not because, as has
been conjectured, the coating acts as an insulator, but as a functionally
new material formed by the interaction of the elements atoms and the atoms
of the coating. This new material is more or less impervious to
reduction/oxidation effects and electric/reduction firings can be
undertaken without changing the elements any more often than conventional,
uncoated elements in conventional electric kilns. Probably less often, in
fact.
In practical terms, it is best to apply ITC213 to new elements,
install them and fire to temperature to initiate the bonding. Then spray
the interior of the kiln with ITC100HT (not necessary, but recommended).
If you have an older set of elements (in reasonably good condition) in a
kiln that you want to reduce, just spray the entire interior with
ITC100HT. This will give you about a 40% increase in effectiveness and
will certainly extend the element life far beyond normal.
ITC213 is recommended for burner heads a simple, light spray will
do. This will greatly extend the life on burners used for salting.
Finally, there have been requests on Clayart for recommendations
of setters or kiln shelves. My suggestion is to purchase inexpensive
cordereite setters (shelves) and coat them (on both sides and edges) with
ITC100HT; it will raise their effective temperature rating 100-150
degreesF. --easily cone 10. The material works because it forms an
isolating matrix with the parent ceramic body (molecularly). I like to add
a coating of ITC296A which provides a smooth surface. With either no kiln
wash is needed.
If you have read this far you may know more than you want to know,
but hopefully this has explained a little about what the ITC coatings are
and what they are not. And, finally, the coating materials are not simple
alumina/zirconia mixtures.
Regards to you all, Nils Lou
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