Q: I want to make a small sculpture in plastiline (oil-based) clay. I want
to create extremely smooth flowing curves, with no tooling marks. What is
the best way to achieve this result?
A: You can try making an initial plaster mold, a piece mold or a waste mold.
This affords you the opportunity to sand on those tricky convex curves while
they are concave, and vice versa, before casting wax or another material
into the plaster mold to achieve a positive. Plaster is easy to sand smoothly.
Here are a few more things you could try:
1. Forget about the plastiline and use potter's clay (without grog). This
is a whole lot easier to smooth out. Use rubber potter's "ribs"
and damp sponges for the final smoothing. The main problem is keeping the
thing from drying out and cracking up- especially if you're using an armature.
But misting and the use of plastic bags can slow down the drying process
considerably, and the "leather hard" stage which clay goes through
as it dries gives you a chance to make sharply cut edges, if called for
in the design.
2. By carefully cutting curves out of flexible plastic ( I've used the kind
that is used for blister-packs- like Avery labels come in) you can make
smoothing tools that can be dragged along the contours you are trying to
create. Try filing or sanding the edges to make them absolutely smooth and
taper them toward the edge (if you can do it without sacrificing the curve's
accuracy.) As you drag it along the surface, you can change the bend in
the tool to accomodate changes in the contours. If you make a series of
these, in graduated convex and concave shapes, you can handle most of the
range of troughs and humps you encounter. And you can use them like cabinet-maker's
molding scrapers as well, by cutting a profile of the desired ogee, beading,
or other decorative detail into the working face.
3. Use lubrication and a piece of chamois for final smoothing. Some sculptors
like to use oil, which works okay for waste-molds, but it's not so great
for rubber-molding. I like using soap for this- either liquid dish soap
or tincture of green soap. The lubricant keeps the clay from smearing, which
is most of the problem with plasticine. You only want to do this after you're
finished adding clay, since new clay won't stick to the soapy surface. For
really small areas, you can wrap some chamois or other light leather around
an appropriately shaped modelling tool, or use pieces of a stiffer leather-
I used scraps of tooling-grade leather sanded on the fuzzy side to form
sharp smooth edges, and made a set of flexible smoothers in variously curved
shapes. Some people favor lighter fluid and a soft brush, or wax solvents,
but these can be toxic and/or flammable and I haven't tried them.
4. You can also experiment with different densities of flexible foam. Places
that set up kayaks and canoes might be willing to donate some scraps of
the material they use for boat pillars and seats, which is quite a bit denser
than the type used for upholstery. I've also used some new-type modeling
tools with stiff but flexible foam tips mounted like brushes that seemed
to be designed for this sort of thing. They are called "Clayshapers"
and are made by Forsline and Starr Intl. Ltd. P.O. Box 67 Ware, Herts, SG12
OYL England, also Box 278 Lyons, PA 19536 USA. I particularly liked the
flat chisel-pointed version, although there are five tip styles available
in four graduated sizes, and all of them seem like they would be useful
for some applications. Leslie Ceramics (linked to my page under Resources/Materials/Ceramics)
has some of these in stock.
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