The Hendriks on thu 29 nov 07
jim bob,
=20
My students and I often use WD-40 in the studio to release slab made plates=
from plastic moulds. We have found that if there is too much WD-40 it can =
collect in texture or cracks and widen them usually resulting in the demise=
of the piece. Doesn't WD stand for Water Dispersal or something like that?=
My theory is that replacing water with WD40 disturbs the wet structure of =
the clay. If my theory is correct, blotting most of the WD 40 off of the st=
amps before using them and removing any that collects in the imprints -perh=
aps with a foam brush -before it has time to seep in, should prevent cracki=
ng.
=20
Let us know what you figure out!
=20
Blessings,
Eleanor
=20
> Date: Thu, 29 Nov 2007 00:04:01 -0600> From: jsalazar@SULROSS.EDU> Subjec=
t: cracking from rubber stamps> To: CLAYART@LSV.CERAMICS.ORG> > hey there a=
ll,> > i have a student who is making very nice shallow bowls, bakers and> =
casseroles. while the pots are still on the bats she is rubber stamping> de=
signs into the bottom of them. the stamps are about 1/16" to 3/32" deep> an=
d every one of them is cracking. the cracking is starting from inside> the =
stamped image and cracking outward. no "s" cracks or any other> cracking go=
ing on, only cracking that radiates from the stamped images. > she is throw=
ing on bats and is using cone 10 stoneware, spritzing the> stamps with wd-4=
0 and stamping the pots. does anyone have any ideas why> this might be happ=
ening?> > thanks for your time and consideration,> > jim bob> > ___________=
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Dannon Rhudy on thu 29 nov 07
I would think, Jim Bob, that there is some uneven
drying going on, and after she has thrown and
stamped one she should cut it in half and look at
the cross section. I suspect that the stamped part
is significantly thin, drying faster, and pulling apart
from the thicker portions.
Once dry, she should have no trouble firing. Maybe.
Have her try waxing the bottom of the bowls, including
all the stamped area and up the sides an inch or two,
and see if the problem persists. Wax inside and out,
if she gets that far, though sometimes inside wax is
enough to even things out.
regards
Dannon Rhudy - and Merry Christmas, Jim Bob
Jim Bob Salazar on thu 29 nov 07
hey there all,
i have a student who is making very nice shallow bowls, bakers and
casseroles. while the pots are still on the bats she is rubber stamping
designs into the bottom of them. the stamps are about 1/16" to 3/32" dee=
p
and every one of them is cracking. the cracking is starting from inside
the stamped image and cracking outward. no "s" cracks or any other
cracking going on, only cracking that radiates from the stamped images.=20
she is throwing on bats and is using cone 10 stoneware, spritzing the
stamps with wd-40 and stamping the pots. does anyone have any ideas why
this might be happening?
thanks for your time and consideration,
jim bob
Gail Fullerton on thu 29 nov 07
Don't stamp until the pots are off the batt and the clay on the bottom ca=
n
shrink freely.
I routinely stamp the bottoms of thin items and have had no problems at a=
ll.
Gail Fullerton
in sunny and beautiful Fairbanks Alaska
____________________________________________________________________
=
Michael Wendt on fri 30 nov 07
Jim Bob,
We have observed similar effects if the edges
of the rubber stamp are very sharp. I suspect
that faintly rounding the edges of the design
features with very fine Scotch Brite will solve the
problem as it did for us. I also suggest your
student remove as much water as possible,
rib and allow the surface to dry a while before
stamping to reduce the cracking.
Sharp nicks and scratches can also become
cracks due to the same phenomenon that
allows a scratch made by a glass cutter
to control where glass breaks when subjected
to a bending moment. In clay, the cracking
engine is shrinkage caused by water loss
during drying.
Regards,
Michael Wendt
Wendt Pottery
2729 Clearwater Ave.
Lewiston, Id 83501
U.S.A.
208-746-3724
wendtpot@lewiston.com
http://www.wendtpottery.com
http://UniquePorcelainDesigns.com
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