barbara lund on fri 2 may 97
I wonder if any one has any idea what my problem can be. I make ceramic
drums in 2 parts-the bottom I call the tower and the top I call the bowl.
Both sections start out with the same amount of clay. With the larger
drums, 5 or 6 lbs per section, some of the towers make a spiral jagged type
crack several hours to several weeks after they have come out of the kiln.
Usually they wait until I have gone to the bother of putting their heads on
and then crack. I cannot tell the difference between those that do crack
and those that don't-same glaze, shelf, claybody (Minnesota clay MB white
stoneware), glazed both sides or only one. Usually it is the most beautiful
drums that crack. The crack starts at the bottom of the tower and spirals
up almost to where the bowl is joined to it. Any advice would be welcome.
Oh, I fire cone 6 electric and try not to rush cool the kiln too often. Thanks
Barb Lund
barblund@bluemarble.net
Ron Roy on sat 3 may 97
>----------------------------Original message----------------------------
>I wonder if any one has any idea what my problem can be. I make ceramic
>drums in 2 parts-the bottom I call the tower and the top I call the bowl.
>Both sections start out with the same amount of clay. With the larger
>drums, 5 or 6 lbs per section, some of the towers make a spiral jagged type
>crack several hours to several weeks after they have come out of the kiln.
>Usually they wait until I have gone to the bother of putting their heads on
>and then crack. I cannot tell the difference between those that do crack
>and those that don't-same glaze, shelf, claybody (Minnesota clay MB white
>stoneware), glazed both sides or only one. Usually it is the most beautiful
>drums that crack. The crack starts at the bottom of the tower and spirals
>up almost to where the bowl is joined to it. Any advice would be welcome.
>Oh, I fire cone 6 electric and try not to rush cool the kiln too often. Thanks
>
>Barb Lund
>barblund@bluemarble.net
The glaze winds up too big for the clay - at cone 6 there is probably not
enough cristobalite to be a problem so I know it's the glaze - there, you
see I did it - blamed it on the glaze when it can never be the glaze alone
- It's always the clay and the glaze. It's easy to do cause I know I can
usually do something about the glaze. If the clay is bought you have to
adjust to it.
Ron Roy
Toronto, Canada
Evenings, call 416 439 2621
Fax, 416 438 7849
ronroy@astral.magic.ca
Mitchell Cutler on sun 4 may 97
Ron Roy wrote:
>
> ----------------------------Original message----------------------------
> >----------------------------Original message----------------------------
> >I wonder if any one has any idea what my problem can be. I make ceramic
> >drums in 2 parts-the bottom I call the tower and the top I call the bowl.
> >Both sections start out with the same amount of clay. With the larger
> >drums, 5 or 6 lbs per section, some of the towers make a spiral jagged type
> >crack several hours to several weeks after they have come out of the kiln.
> >Usually they wait until I have gone to the bother of putting their heads on
> >and then crack. I cannot tell the difference between those that do crack
> >and those that don't-same glaze, shelf, claybody (Minnesota clay MB white
> >stoneware), glazed both sides or only one. Usually it is the most beautiful
> >drums that crack. The crack starts at the bottom of the tower and spirals
> >up almost to where the bowl is joined to it. Any advice would be welcome.
> >Oh, I fire cone 6 electric and try not to rush cool the kiln too often. Than
> >
> >Barb Lund
> >barblund@bluemarble.net
>
> The glaze winds up too big for the clay - at cone 6 there is probably not
> enough cristobalite to be a problem so I know it's the glaze - there, you
> see I did it - blamed it on the glaze when it can never be the glaze alone
> - It's always the clay and the glaze. It's easy to do cause I know I can
> usually do something about the glaze. If the clay is bought you have to
> adjust to it.
>
> Ron Roy
> Toronto, Canada
> Evenings, call 416 439 2621
> Fax, 416 438 7849
> ronroy@astral.magic.ca
Hi,
I've been making lamps and have had cracking problems, though not in a
spiral. How do you dry these before your fire them? I've found that I
must air dry at least 5 days then overnight in my kitchen oven before
firing. Also, I've had good luck with scraping the clay around a crack
into the crack on the rims of bowls. Maybe scraping over the surface of
the dry greenware before bisque will strengthen it so it won't crack
after the glaze or later.
June Rosenberry
4119 Edenhurst Ave.
Los Angeles, CA 90039
213 664 8306
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