Stephani Stephenson on sun 10 dec 00
First: to revisit the warping tile...try putting slabs through the
slab roller twice, and turn the slab over in between times. Possibly a
differential in clay particle compression and orientation is occurring
due to the dynamics of your slab roller. This would affect water
evaporation and could cause deformation in drying.
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Somewhere along the way, I was taught to put grooves on the backsides
of slabs to reduce warping .
I often use this technique , scoring one side of the slab with a wide
tined tool or a large notched trowel.
I especially use it for large slabs or large tile that will not be
moved or turned in drying.
The reasoning behind this technique is to allow allow air circulation
into the underside of the slab during the drying process, thus promoting
more even evaporation in drying.
The second reason, and I cannot say if I was taught this or if it is
just a strong image in my mind , is that that these notches or score
marks structurally alleviate and minimize warping by taking up the
slack, so to speak. I know that is a very vague phrase and I don't have
a clear verbal analogy for the image I have of what happens. The only
other analogy that comes to mind is how one cuts notches in a seam
allowance, to allow for freer movement and distribution of stress in
fabric. However that is usually done while attempting to MAKE a curve
not prevent one, so it is not a great analogy. I can't honestly say if
this second reasoning holds true or if is just a comforting process ,
part habit, part imagination, on my part!
However, after reading about Paul's friend's concept of inducing
plastic amnesia, (great phrase!), I wonder if something similar is
going on here. Rather than dropping a slab, i.e., SHOCK induced
amnesia; scoring or notching the slab or tile would be more like
SURGICALLY inducing plastic amnesia. Cutting away strips, so that the
clay cannot possibly remember , on the whole, what it is that it was
supposed to do. In other words, carved grooves or slashes would serve to
interrupt the molecular layers as they slip and slide into a
previously predetermined pattern which says warp, baby , warp!
OH SURE, the individual segments might still remember ,but they can no
longer get in touch with the other segments, because the phone lines are
down. OH SURE, they could hit the muddy backroads in their little
hexagonal ion powered claymobiles , but that is like driving to Cutbank
when trying to get from Missoula to Butte. Yes, my pretties, it will
all be dessicated and done with by the time you get there!
But , ahem, I digress, and it's suddenly looking quite gruesome in
that little ol slab.
Seriously though,
I can say I have always had very good success with drying in all manner
and shapes and sizes of tiles and slabs.
Nowadays I don't usually notch or score the clay, but I'm using
groggier clay and not firing so high.
Also I always thought the prestamped or premolded grooves on the
bottoms of the commercial tile had more to do with improved adhering
of tile during installation, but I do not know that for a fact.
Certainly it gives the tile a finished look.
I have pressed or carved indentations this on large or thick tiles ,
simply to lighten the weight of the piece, to allow for a better
interfacing of tile and adhesive, and again to improve air circulation
around and into the piece.
Stephani Stephenson
mudmistress@earthlink.net
Leucadia CA.
reminder to self: watch out about writing posts during full moon
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