Sue Beach on mon 12 mar 01
Hello group,
I have a new extruder (Scott Creek) and have just begun to experiment with
it. I have both of the new extruder books and have begun reading them. I
have a couple of questions, however.
When I extrude a hollow form, it curves severely. How do I correct this so
it is straight?
Also, the clay tears once I've extruded the form. This is after it is out
of the extruder and on my work table. It tears along the corners if the
form has them.
Any suggestions as to what I am doing wrong?
I have not yet successfully extruded anything!
Thanks,
Sue Beach
in Central Indiana where it keeps trying to act like Spring, but hasn't
quite succeeded
slest12+@PITT.EDU on tue 13 mar 01
Hi Sue,
I just got a Scott Creek extruder too, and I'm having a blast playing with
it. I don't have a vast amount of experience to draw on, so hopefully
someone more advanced will also chime in. To get hollow forms to come out
straight, I found it helpful to make sure the center part of the die is
*absolutely* in the middle of the outer piece. If there is unevenness in
the wall thickness, I think the clay passes through the wider part of the
opening a tiny bit easier than the thinner part - comes out faster on one
side and makes the whole thing curve. There isn't much room to play with
in the die positioning, but try fiddling witht the die by rotating the
center and outer portions with respect to each other before putting the
hoding pins in and filling the barrel with clay. Also, I found I could
minimize any residual curving by holding one hand on the bottom of the
extrusion as it is emerging from the barrel.
> Also, the clay tears once I've extruded the form.
Maybe the clay is too soft? I have been working with very soft clay in the
extruder, but I let the extrusions set up a bit before doing anything with
them. As I make the hollow extrusions, I stand them vertically in an empty
clay box lined with a drycleaning bag and a sheet of newsprint to keep the
sticky-soft clay from sticking to the plastic. A box with cardboard
dividers from the liquor store would be even better, but I didn't get
around to that yet. I'll leave them standing there with the bag open for a
couple of hours, minimum, then wrap and wait overnight. Best results if
the pieces are flipped (top-to-bottom) occasionally and have a couple of
cycles of having a few hours of airing, then re-wrapping and standing
overnight. I don't try to lay the pieces on their sides until they are set
up, otherwise they flop all over the place and crease and tear.
Have fun and good luck,
Susan Erickson
Cindy Strnad on tue 13 mar 01
Hello, Sue.
When you're extruding a hollow form, be careful that you have the die
arranged so all the walls will be equal in thickness and profile. This is
especially important for the non-round forms. Mine do tend to want to curve
a bit anyway, but I guide them with my other hand as I extrude, and this
seems to solve that problem.
It sounds to me as if your clay might be too dry or not sufficiently
plastic. Or possibly it has an unequal moisture content. Try wedging it well
before placing it in the extruder. If you're already doing that, you may
want to try a slightly moister clay. If your clay is intended for
hand-building or sculpting, or is just high in grog, you may want to try a
grog-free body which is advertised for wheel work.
Hope this is of some help,
Cindy Strnad
Earthen Vessels Pottery
RR 1, Box 51
Custer, SD 57730
USA
earthenv@gwtc.net
http://www.earthenvesselssd.com
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