David Hendley on tue 4 aug 98
It's hard to know when to throw out old kiln shelves, Joy.
I'm still using my 12 X 24 silicon carbide shelves from 1975
(cost: $18 and change each!) and virtually every one is cracked.
Some have cracks down the center of the long dimension;
some have 2 cracks going across the 12" dimension, one from
each side, each one more than half-way across.
This probably sounds like a disaster waiting to happen, but
not one shelf has broken in the last 6 or 8 years.
Through the years, I have experienced a couple of shelves
breaking during a firing, but the results were far from
spectactular. The weight of everything above the broken
shelves held the two pieces pretty well in place. Maybe one
or two pots under the break were damaged. No big deal.
I can't speak for other kinds of kiln shelves, but silicon carbide
has years and years of life after it cracks.
David Hendley
Maydelle, Texas
At 07:52 AM 8/3/98 EDT, you wrote:
>----------------------------Original message----------------------------
>the bottom shelves yes the ones that
>support the entire stack on shelves had broken, both shelves. Broken apart
>folks. I've been watching these old shelves, noticed the cracks 10 firings
>ago but didn't replace them. I'm a boot strap organization. I had placed an
>extra post under the shelves on the other side of the cracks & that is what
>both saved the entire stack of shelves & probably stressed the crack to the
>breaking point. Not a single tile was broken. The shelf pieces landed on a
>2nd planter I' threw in at the last minute because it fit in the space, the
>shelf hunks braced up against it & saved other pieces from damage. What a
>close call. New shelves are a tax write off but all my labor making the
tile,
>glazing etc isn't. Along with investing in the best kiln inspect & reject
>those questionable shelves my friends. Joy in Tucson
>
John K. Dellow on wed 5 aug 98
Re : silicon carbide shelves cracking. I have seen this avoided by cutting a 1/1
th nick at the center point in each side i.e. 4 cuts per shelf. The first was by
german potter in sydney Australia & the second was in Kyoto Japan.
You need to use a new diamond blade in a brick cutting machine. The german was
firing art ware in an electric kiln . The Japanese was doing oil spot tenmoku in
electric & oil fired kilns.
John Dellow
Keep away from the hard clay :)
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