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Clay Modeling Materials
What is Plastilina?
Plastilina is a wax- and oil-base modeling material
used by sculptors for modeling pieces. Plastilina can also be referred to as plasteline, plasticium, and plasticine.
The main ingredients are wax, oil, and clay flour that is used as a binder. All plastilina is produced hot, and
then cooled and extruded into the shape that will eventually be available for sale in art supply stores.
Plastilina is used as a modeling material only and cannot and should not be fired in any way. Plastilina cannot
be made permanent. A mold of plaster or rubber must be made to obtain a finished piece.
What are the types of Plastilina?
There are basically three groups of plastilina: professional grade, school grade and industrial grade. The professional grade plastilina commonly contains
sulfur, to make the smoother, more homogeneous texture required by professionals. ROMA Plastilina
is an oil- and wax-base modeling material preferred by professional sculptors. A non-sulfur professional
grade material in medium consistency, called Prima Plastilina, is also available. The school grade,
or amateur grade plastilina, does not contain sulfur and tends to be stiffer and harder to model with
the fingers. School grade plastilina comes in a variety of striking colors and is used in the Claymation
field of movie production and advertising. The industrial grade plastilina is usually very hard and needs
to be heated prior to use. This type of plastilina is most commonly used by designers in the automotive
field for car models and is not available to the retail consumer.
How can I soften and harden Plastilina?
To soften plastilina, if not being used at room temperature, 68° - 70°, place the
material approximately two to three feet from a 60-watt
light bulb for about twenty minutes. To change the grade
consistency, soften the clay as instructed above by placing it near
a light bulb and knead in small amounts of oil until an even consistency is achieved.
While some people microwave plastilina, it is not
recommended for plastilina containing sulfur since
people tend to overcook the material. If you do attempt
to microwave plastilina containing sulfur, be careful -
the plastilina is melted to a more liquid state and
since the component parts contain sulfur, it might
smell. The basic formula for plastilina is wax, oil and
clay flour so take this into consideration before doing
something that you may regret later!
Non-sulfur plastilina can be placed in a microwave oven
to soften it for use, but since microwave ovens have
different power levels and wattage varies, there is no
one set rule for successfully heating the plastilina -
accomplish this by trial and error.
To harden plastilina, place it in the refrigerator for thirty to
forty minutes before working with it. There is no
technique for permanent hardening. To change the grade
consistency,
soften the clay as directed above and add softened Microcrystalline Wax in small amounts to
the material by kneading it into the softened plastilina until the desired consistency is achieved.
How can I restore dried out Plastilina?
Knead household oil, a few drops at a time, into the material
until you have acquired the desired consistency.
How can I correct color inconsistencies?
This is not easily done since the raw materials
will vary from batch to batch. While manufacturers cannot guarantee
the production of totally accurate color batches from materials received
from the pigment producer, they work hard to achieve the closest possible
color consistency. Purchase in batch lots if possible if accurate color
consistency is absolutely necessary. Remember the plastilina is only a
model to be cast and is not the finished piece. Most of the time the
color will be extremely close, but as with everything made of natural
ingredients it may vary.
How can I correct uneven consistencies?
Since the raw materials are of natural origin they will vary. Although manufacturers
attempt to guarantee consistency, composition changes over long periods of time cannot be avoided.
Consistency will be the goal of the manufacturer but may not always be achieved.
Hardness. This is regulated by the ingredients in the specific formula
and, depending on the variation of the raw materials, may differ slightly, although not
commonly. During temperature changes in the weather, the material will also change slightly;
in the summer, the material seems softer and in winter months, it may seem harder. Sitting at
room temperature for eight hours, all plastilina should return to its stated hardness.
Short-Dry Material. This is caused by lack of wax or oil, or may occur because the
manufacturer has not aged the plastilina (that is, allowing it to mature for several weeks,
if not months, before packaging). Add household oil or return the material to the supplier.
How can I make Plastilina permanent?
You can’t. A mold must be made and a cast drawn for the final piece.
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