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kiln shelf problem-thanks

updated wed 18 aug 04

 

Eleanor on tue 17 aug 04


Eleven people responded to my query--thanks to all of you.

Some questioned or assumed I was using porcelain; my clay is Tucker's
Smooth White.

Almost all agreed that alumina either on the shelves or mixed into
the wax or both was the solution. I had seen references to alumina in
the Archives but didn't think it applied to me since this was a _new_
problem and I had made no other changes in my glazes, application
techniques or kiln prep except to add slow cooling to the routine.

I will take the advice I was given and will report on results. No
breath-holding please; I work slowly and fire infrequently.

I remain puzzled but I guess I'll get over it especially if the
plucking (I learned a new word!) stops.

Gratefully,
Eleanor Kohler
Centerport, NY

Anne Webb on tue 17 aug 04


hey eleanor..

One more thing...I was just looking at a page that had a listing of all the
tuckers clay bodies.. i forgot that smooth white is a cone 6 clay. i've used
it but i couldnt remember.

considering you are firing cone 6, alumina might be a bit of overkill.
people use alumina for high fire porcelain which has a real tendency to
stick to shelves and itself in a glaze firing. although you could buy a
small bit of alumina and add it to your wax.. its great for lids and
galleries.

my teacher in toronto used to fire cone 6 and his shelves were in less than
ideal shape. he would sprinkle a little silica sand right under a pot..
really doesnt take much..a layer maybe 1 grain deep. (he also used a little
bit under his kiln posts, when needed, to make them sit firm and not
wobble.) the silica sand, like alumina, acts like ball berrings between
your pot and the shelf. he said it helped ease the strain on the pot during
expansion and contraction during firing.

if you decide to try this, you need to pay special attention to where the
sand goes.. you cannot just broadcast it like seed, you have to place it
deliberately to protect your work below. also, upon reloading your kiln, you
need to brush off your shelves well before putting them back in the kiln.

i like the idea of adding the alumina to wax because it stays localized on
the bottom of your pot instead of all over your shelf, where it could fall
onto work below. i havent tried adding silica sand to wax, but i bet that
would work too, just it would settle quicker than the alumina...?

silica sand is way cheaper than alumina.

Take care. anne

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Rod Wuetherick on tue 17 aug 04


Dry Alumina Hydrate on shelves - Out of more than 1000 firings or more I
have never and let me repeat never had dry Alumna hydrate hurt/damage any
pots. Though I have seen many a pot ruined by flaking kiln wash.

Cheers,
Rod


i like the idea of adding the alumina to wax because it stays localized on
the bottom of your pot instead of all over your shelf, where it could fall
onto work below. i havent tried adding silica sand to wax, but i bet that
would work too, just it would settle quicker than the alumina...?