John Tilton on sun 1 jun 97
Last March I made several large 28 inch platters and had to dry them
quickly. They were somewhat complex in design and I was afraid to just
cover parts of them. I always dry stuff right side up because the
bottoms seem to stay put better that way. My solution was to dry each of
them on 2 layers of terry cloth towel. I was astounded by how evenly
they dried. The towels just wicked the moisture away. They were totally
dry in 8 days.
John Tilton
Alachua, Fl
Wilkinson on mon 2 jun 97
Living in a dryer climate, I use a larger piece of plastic from a
drycleaners. I cut a 2 -3 inch circle out of it placing that opening over
the center of the platter with a piece of cloth over that. Each day I cut
the opening a bit larger and replace it over the platter. This helps it to
dry from the center out and eliminates the edges from drying too fast and
the cracking. At the same time it drys quickly.
Lori Wilkinson
Rowell NM
LorWilk@dfn.com
Bryan Hannis on fri 1 dec 00
Have you tried bisque firing them standing vertical in the kiln?
Bryan Hannis
Pancioli on sat 2 dec 00
In my experience platters crack from EDGE to CENTER because they are
rested on their rims when turned upside down--for trimming thrown pieces
or for adding feet to handbuilt platters. The rim edge dries more
quickly than the rest of the platter and it can't take the weight. The
hair line cracks caused this way can't be seen until after the bisque.
My students are taught to turn their large handbuilt platters onto three
layers of foam (inside the platter) which leave the rims hanging in air
when they are turned upside down for the addition of feet. We have few
cracks and make many large platters every semester.
The other occasion of cracking I have seen is when platters are fired
too fast--and the edges heat and shrink before the center has a chance
to heat up.
One other cause is that the rims are too thin compared to the rest of
the body and the difference in thickness causes the cracking.
We fire large platters on their feet-- no grog, no hole in foot, slowly
and don't have any problems.
Diana
Judy Rohrbaugh on wed 2 mar 05
I usually have good results with items not cracking, I used to make up to
18' platters, firing up to cone 9.
What I do is dry things out very slowly and as evenly as possible, this is
done by keeping items under plastic, and checking.
When I did platters, I would let them dry a bit upside down.
Also, fire slowly in your bisque, and to make a real mess, fire on sand.
I am curious as to how your platters are exactly shaped.
Judy Rohrbaugh (new member trying to give advice already)
_fineartstoneware@aol.com_ (mailto:fineartstoneware@aol.com)
Silver Lake, OH, USA
Vince Pitelka on wed 2 mar 05
> Also, fire slowly in your bisque, and to make a real mess, fire on sand.
I don't want to be a curmudgeon. Really I don't. But I get slightly
apoplectic every time someone suggests bisque-firing with sand under a
piece. This is, in fact, one of the very worst things you can do. Movement
is not the issue, because shrinkage in bisque firing is non-existant or
negligible. Assuming that there are not structural flaws already present in
the piece (for example, due to unidirectional slab-rolling, or uneven
drying), then the most common cause of cracking in bisque firing is uneven
heating and cooling. Sand INSULATES the bottom of the piece from changes in
temperature, and that is the last thing you want.
You say that you fire your platters on stilts, and that is good. Do the
stilts support the platter evenly? For large flat-bottom platter or flat
slab forms, I use a network of stiff clay wads, just soft enough so that the
platter can be nestled down on them, contacting all wads evenly. For footed
platters I use a starburst arrangement of coils of clay wadding. Mix your
wadding 50-50 flint and any clay, and you don't have to worry about the
wadding being damp when you start the firing.
Good luck -
- Vince
Vince Pitelka
Appalachian Center for Craft, Tennessee Technological University
Smithville TN 37166, 615/597-6801 x111
vpitelka@dtccom.net, wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka/
http://www.tntech.edu/craftcenter/
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