Nancy Jonnum on fri 4 mar 05
I have made a rather large sculpture of a llama. It is about 28" high. It
has a neck which extends a ways forward from the body (just as real
llamas do). I have heard of people using fire brick or other things
under these extensions to support them diring firing, but I have never
tried it. I would love to know how people on the list would handle this
situation. Would you support It? If so, how would you suggest doing
it? Many thanks for your help.
Nancy J.
Ceramic Design Group on fri 4 mar 05
Hey Nancy,
We had Richard Notkin at Ceramic Design Group for a workshop this past
November, and he mentioned that he uses 'shrink slabs,' made out of
the same claybody, to fire his intricate teapots on. The shrink slab
accounts for the lateral shrinkage. The sculpture and supports go on
the slab, and, by the way, I would make the supports out of the same
claybody, then everything should shrink together at the same rate. Put
some grog between the kiln shelf and the shrink slab. Another thing he
mentioned is that sculptors and potters should never fire together -
sculpture needs to be fired at a slower rate. Email me off list for
more info, if you need it.
Good luck!
Annie Chrietzberg
Ceramic Design Group
Steamboat Springs, CO
On Mar 4, 2005, at 8:38 AM, Nancy Jonnum wrote:
> I have made a rather large sculpture of a llama. It is about 28"
> high. It
> has a neck which extends a ways forward from the body (just as real
> llamas do). I have heard of people using fire brick or other things
> under these extensions to support them diring firing, but I have never
> tried it. I would love to know how people on the list would handle
> this
> situation. Would you support It? If so, how would you suggest doing
> it? Many thanks for your help.
> Nancy J.
>
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Chris Leake on fri 4 mar 05
If you use firebrick as the major portion of your support I would recommend using a wad of your sculpture clay as the last part of the armature. It has been my experience that it shrinks/expands better with your sculpture during the firing.
Mostly just a reader,
Chris Leake
Snail Scott on sat 5 mar 05
At 10:38 AM 3/4/2005 -0500, you wrote:
>...I have heard of people using fire brick or other things
>under these extensions to support them diring firing, but I have never
>tried it...
Whether it needs support at all will depend
on the pyroplasticity of your clay body, the
amount of torque on that extended part (a
product of its weight and the horizontal
distance from its attachment,) and how high
you fire. A body prone to warping may be
fine if fired a cone or two lower.
Remember the nominal 'firing temperature' of
any clay is a compromise between the desired
amount of vitrification, pyroplasticity, and
possibly other factors such as appearance,
thermal-shock resistance, fit of a favorite
glaze, tendency to bloat, etc. The right
temperature for one application may not be
the same as for another. Firing lower is not
a suitable response to every warp-prone form,
but it is an option, especially if it won't be
glazed to match other work. The clay will not
be as strong, but this is relative, too. No
clay is infinitely strong; the question is,
will it be strong enough for your purposes?
Many clays are routinely fired lower than their
optimum balance of strength and vitrification
versus warping or bloating, not from intention,
but because the manufacturer named a cone, it
worked well enough at that temperature, and
the user never tried any other temperatures.
So, the essential question is, will your clay
body tend to warp in this circumstance? And if
so, do you need to maintain that temperature
anyway?
If it might, and you do, then propping it is
certainly an option. (I might just fire that
bit separately and attach it later, but that's
me.)
Propping with brick has the basic problem that
the bricks won't shrink with the clay. One way
around this, which I've used, is to stack the
bricks to the expected level of the clay AFTER
shrinkage, since it probably won't need the
support until the highest temperatures anyway.
Another method is to make a support of clay,
which will shrink in tandem with the clay object.
This works well. It does result in a useless
chunk of fired clay, but I don't see that as an
issue. It's not much of a waste, compared with
messing up a major piece of work.
One consideration for your project is the shape
of the llama neck: you may need to prevent warping
toward the front and also toward the sides, and
that's a lot of support. I would suggest making
towers of bricks to each side and front if there
is space, and having brick or clay projections
extend toward the neck as 'bumpers' if it should
bend that way. Since the shrinkage will mostly
be vertical, the neck will be free to shrink
downward, and the slight sideward sway will not
look too bad if it does tip toward one of your
bumpers.
I hope this applies to your project in some
useful way!
-Snail
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