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advice sought for larger sculpture - long

updated wed 19 aug 09


Dannon Rhudy on mon 17 aug 09

Carl, to keep a large piece evenly moist, in any climate,
the best thing is a damp sheet, covered with plastic. Rodin
used to use wet cloth to keep his works in progress damp,
and it seemed to work for him. He sent someone to make
the rounds of his various studios (he had several) every day,
to make sure the coverings were properly damp. Since you
will be able to check on your own,. a cloth covered with plastic
should work very well. You should not need a humidifier.

It would be best by far to work directly on the kiln shelf(s),
in place if possible. It is difficult to move greenware of size,
especially if it must then be lowered into a kiln. If in fact you
MUST move it after it is done, do it before it dries. Additionally,
fire it exceedingly slowly - Don Reitz sometimes lets his large
forms dry for months before they are fired, and then takes
several days to reach temp. If you take the trouble to wedge
chopped nylon fiber into your clay before you use it for your
sculpture, you will have far less trouble with cracking. Thickness
of the piece will affect drying, too, as well as firing time.

I've made and fired life-size porcelain sculptures, and used
nylon fiber to hold the lot together while I worked and while
it dried. Wall thickness was about an inch, I used a coil
method. Cracking was not an issue. I wedged the nylon
into the clay about ten pounds at a time, since it was a boring
chore. Doesn't take long, though. If you have your own
mixer, you can put the fiber in when you make your clay.
All the easier, then.

I might further suggest that you try this method on something
simpler and smaller than your sculpture. Perhaps a large/tall
pot, using the same clay and building technique you plan for
your other work. It will go quickly, teach you about what
you'll be doing/working with, and you can fire it or not, as
you choose.

It's interesting to take pictures as you go, or make sketches,
and keep a log, of sorts. You'd be surprised what you DON'T
remember, second time through.


Dannon Rhudy

I''m planning on a life size model sculpture and am seeking adivce on a
number of things, both aesthetic and technical

Ann Brink on tue 18 aug 09

Carl said: (snip)Another thing is I only have a medium sized electric at my
home studio and height will be an issue, I can probably borrow some brick t=
bring it up to height or perhaps a full ring from an old kiln. if I'm going
to at least bisque it here, otherwise I'll be spending a lot of time at
another studio and I'm sure that could get old with such a large

Hello Carl:
I will just comment on one part of your post: One time I made a pot that wa=
several inches taller than my electric kiln, so I added a row of hard brick=
standing on edge, then brought in two 12x24 shelves from my gas kiln and
placed them on top. I used hard brick because I thought the radiation would
help. I put ceramic fiber wads between any spaces between the bricks, at th=
corners, and placed several layers of ceramic blanket on top. It worked all
right both for the bisque and glaze firing.

Ann Brink in Lompoc CA
(mostly about pottery)

Snail Scott on tue 18 aug 09

On Aug 17, 2009, at 7:14 PM, Carl Ross wrote:

> I''m planning on a life size model sculpture...
> this won't likely be done in one sitting so I plan on some sort of
> damp closet especially since I'm in the arizona desert and merely
> covering it won't do the trick.

I lived most of my life in AZ and NM, and most of my
work is sculpture at that scale.

You are correct that just wrapping is a short-term
solution at best, but here's what I do: I use thick
soft cotton knit fabric, saturate it enough to be damp
through but not drippy, wrap the project in that, then
cover with a plastic bag. It needs to be knit in order
to conform closely to the contours of the clay, and it
needs to be cotton since synthetics don't hold the
water well. When you unwrap the piece to work on it,
store the cloth inside the bag to keep it damp, and
when you re-wrap the piece, spray the cloth with water
before you put the bag back on. If you can't work on it
regularly, spray the cloth weekly, and check on the
moisture level by poking the clay: too dry - spray more
often; if too wet, spray less. The fabric also absorbs
and redistributes the moisture that can condense in
the top of the bag. I've kept 'stalled' projects workable
for six months this way, and probably could have done
so indefinitely.

> Another thing is I only have a medium sized electric at my home studio
> and height will be an issue, I can probably borrow some brick to bring
> it up to height or perhaps a full ring from an old kiln. if I'm going
> to at least bisque it here, otherwise I'll be spending a lot of time
> at another studio and I'm sure that could get old with such a large
> undertaking...

Instead of this, just fire in sections. An electric
kiln makes it easy to get consistent repeated
results even if the parts of the piece are fired
separately even weeks (or years) apart.

You can make it with built-in joints, or cut it
apart when leather-hard. Either way will work.
For a piece as small as you describe (large
for you, but not large in absolute terms), I
would plan to make it in one piece and cut
it apart when it's stiff enough to do it without
causing warping during drying, but before it
dries completely. (It's tougher to cut at that
point, and easier to damage accidentally.)
After firing, reattach the sections permanently
with a paste epoxy. Joints can be fully
concealed, or left as a design element in
more stylized or abstracted work. (If you
want details on this, I can address it later.)

> I'm also curious If I should build it right on a kiln shelf to
> minimize the risk of breaking it and re erect the kiln section by
> section I guess it's safe to say I'm nervous about moving it green,

That's a valid concern. Building right on the
shelf can have advantages, though it does
tie up the shelf in the meantime if you don't
have enough spares to fire other work if you
need to. I generally build on thick drywall
covered with thin nylon gauze, to allow for
free shrinkage while letting the bottom dry
out as I work. I unstack my kiln down to the
floor to load the work, then restack the kiln
around it. A little sand or grog on the shelf
will allow it to move more freely during both
loading and firing.

> The next thing I'm asking for is suggestions on clay body, finish, and
> firing.; first of all I'm looking for a look like that of vitreous
> porcelain but I've never worked with porcelain, and am not familiar
> with how it act in the kiln, and I doubt I'd get a vitreous body
> unless I fire quite high, so that same matte finish is desired in a
> glaze with good fit to a sculpture clay body. I use and have some
> continental clay coarse red, (grogged lowfire body) but I might not
> have enough, So I'm likely going to need to buy clay so I'll likely
> get some thing from laguna since I can order that through a local
> supplier.

As you've no doubt guessed, actual porcelain would
be unwise for anything this large. There are midrange
porcelain-type bodies, but between the very high
shrinkage rate and the pyroplasticity in firing, it's a
setup for a lot of problems.

You can get a porcelain-like appearance by using a
semi-vitreous engobe, which will give a somewhat
more controlled surface than a matte glaze. In fact,
an engobe made from a mid-range porcelain recipe
with much of the kaolin replaced with calcined kaolin
might be a good place to start.

You definitely want a fairly groggy body. I like
ridiculously groggy clay myself, but it doesn't have
to be quite that extreme for good results. Regardless
of the appearance or coarseness of the clay, a
coating of slip or engobe can make it look like
almost anything. It will also have a big effect on any
glaze you apply, if you choose to go that route.

I presently use Laguna's Buff Sculpture clay (WC392, I
think). Whatever you choose, get hold of some samples
to work with before you buy a whole lot of something
you've never tried. Build with it, AND test your surfaces!
Don't put all that effort into anything untested just
because someone else likes the stuff...