Antoinette Badenhorst on thu 17 jun 04
As always I confused the two different cracks with each other. The
straight crack is caused by uneven drying or lack of compression and the
s-crack is caused by water left in the bottom and that weakens the clay
in the bottom. That's from Ceramic Faults and their remedies-Harry
Fraser. Ceramic Science for the potter confirmed that.
Antoinette Badenhorst
105 Westwood Circle
Saltillo MS
38866
662 869 1651
www.clayandcanvas.com
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Dave
Finkelnburg
Sent: Wednesday, June 16, 2004 9:51 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: Drying salad bowls??????????
Dear Randy,
I have to disagree slightly with my friend Antoinette here about the
"cause" of S-cracks. I believe in the potters' adage, "The last part to
dry
is the first part to crack." IF the bottom is thick, or the rim dries
faster than the bottom, you will tend to get S-cracks because the rim is
shrinking in and literally pulling out on the center of the still-soft
base.
It literally pulls the base in two!
Antoinette has suggested some remedies...keeping the bottom the same
thickness as the walls, making sure the bottom is well burnished during
throwing to heal micro-tears in the clay caused during opening.
I would note it is hard (as in impossible) to throw the bottom thin
if
you want to make a trimmed foot. So, you need to get the bowls turned
over
as soon as possible, so the bottom can begin drying, if you plan to trim
the
bottom. Even with a potter's foot turn the pot over soon. If
necessary,
cover the rims as you are doing to prevent them from drying faster than
the
feet. IF you trim a foot, make sure the thickness of the foot is close
to
the same thickness as the walls of the bowl.
Good potting!
Dave Finkelnburg in very dry Idaho where speed drying is
available
year round!
----- Original Message -----
From: "Antoinette Badenhorst"
Sent: Wednesday, June 16, 2004 5:59 PM
> Randy, S-cracks is not caused by drying, but by the way that you
> compress your clay after opening.
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