LaReneM on thu 23 apr 98
I've been using a Laguna cone 5 glaze (colonial white) with a commercial
speckled stoneware clay for two years. Suddenly I'm having problems with slab
pieces breaking as they cool. I bisque to cone 05 and fire to cone 5. I
thought the problem might be opening the kiln too early, so for the last load
I waited until it was 150 degrees. Most of the load survived, but the two
pieces on the top shelf broke. There is no crazing of any sort, the pieces
simply crack, usually just one large crack that runs the length or width of
the piece. I can hear it happen from the next room it's so loud.
I'm guilty of several things... one is not using a witness cone so I don't
really know what cone the bisque and glaze loads fired to (relying on my
controller too much I guess). This also seems to happen mostly with partial
loads.
So great gurus of Clayart, any suggestions for me? I have an order that I'm
late on delivering (a small one thank heavens), but I'm really afraid of what
will happen when I'm gearing up for my next show with large loads. Any
suggestions will be appreciated (except for those about making my own glaze
and clay. We've been over that before!).
Thanks in advance.
Kathy
Midland, Michigan
Bill Aycock on fri 24 apr 98
Kathy- How are these pieces supported on the shelf, or are they directly on
it? Look on the back of the cracked pieces-- is there any sign of places
that stuck to the shelf?
Good luck- sorry I only have more questions.- Bill
At 07:40 AM 4/23/98 EDT, you wrote: *** IN PART ***
>----------------------------Original message----------------------------
>I've been using a Laguna cone 5 glaze (colonial white) with a commercial
>speckled stoneware clay for two years. Suddenly I'm having problems with
slab
>pieces breaking as they cool. I bisque to cone 05 and fire to cone 5. I
>thought the problem might be opening the kiln too early, so for the last load
>I waited until it was 150 degrees. Most of the load survived, but the two
>pieces on the top shelf broke. There is no crazing of any sort, the pieces
>simply crack, usually just one large crack that runs the length or width of
>the piece. I can hear it happen from the next room it's so loud.
>
>Thanks in advance.
>
>Kathy
>Midland, Michigan
>
>
Bill Aycock --- Persimmon Hill
Woodville, Alabama, US 35776
(in the N.E. corner of the State)
W4BSG -- Grid EM64vr
baycock@HiWAAY.net
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