Jennifer Rhinesmith on wed 11 dec 96
To the clayarter who posted the wonderful message about warping bowls.
You had all the steps of things not to do and to do listed out. Well in
my hast to get through my messages I deleted it. If there is anyone who
has a copy of it or the writer could please pass it along again, it would
be most helpful. Thank You very much. Jennifer in Alpine, TX.
Don Jung on thu 12 dec 96
Jennifer Rhinesmith wrote:
> ----------------------------Original message----------------------------
> To the clayarter who posted the wonderful message about warping bowls.
> You had all the steps of things not to do and to do listed out. Well in
> my hast to get through my messages I deleted it. If there is anyone who
> has a copy of it or the writer could please pass it along again, it would
> be most helpful. Thank You very much. Jennifer in Alpine, TX.
Here it is again...(I might add that there was another suggestion that
comes to mind: that we fire lower or use a less vitreous body. This may
reduce warpage since the pieces don't get as soft during the firing and
get less affected by the uneven surface of the kiln shelves. I suppose
the clay body must be such that it still 'matures' even though it is
less vitreous. That's another discussion though...probably implies more
grog or calcined ingredients) anyways here you go...
Re: Warping bowls (Don Jung , 11/25/96 23:37)
To: Ceramic Arts Discussion List
Thanks once again for the generous and informative posts, both on and
off the list. There were quite a few, all with little treasures of
knowledge imbedded. I'll try to sum it up here and do some testing to
confirm which solution(s) solve it for us (we're a group of potter
1.Use really flat kiln shelves or a flat clay pad (of higher firing
clay) underneath to ensure that the bowl's are fired 'flat'.
2.Throw bowls with even thickness throughout with strong rims, not
tapering off or too thin.
3.Fire slowly to ensure even heating. (I believe 150 F/hr to ^6 is slow,
but no one really specified a rate...just the word slowly)
4.Throw bowls with definite changes in curve or shape to provide
strength...similar to a what a stronger(thicker) rim would do.
5.Dry evenly and upside down. (This is not a problem with us as we do
get perfectly round and flat bottomed pieces out of the bisque).
6.Don't stack a 1/2 kiln shelf edge next to the bowl's lip.(related to
7.Ensure the bowl is thrown with a properly proportioned foot...not to
small or too wide and trimmed flat of course.
8.Probably a few more but that covers most of em.
There was also an interesting note from quite a few...that they prefer
the added 'warp' the firing adds to the bowl. I must agree that it does
make a unique and often special piece out of an ordinary one. My only
quibble is that the bottom stay flat and not rock while the rim can sway
just a little.
I suspect our shelves as the culprit...so it's off to do some tests.
Vancouver BC Canada
(more to do...what have I gotten myself into...)