MODELS
Making plaster casts is fun, interesting, and educational. Casts are easy to make and can
be used as teaching aids or display items. Plaster casts are made of specimens you can
not bring home, such as animal tracks.
Plaster casts
Steps to making your cast:
1) Locate the specimen you want to use.
Materials Checklist

2) Make a form by joining cardboard strips to

surround the specimen. The strips can be
joined with paper clips. Use a paper clip to
join the ends of the form. Place your form
around your specimen. If there is soil
around the specimen gently press the form 
into the soil to create a dam.
3) Pour enough Plaster of Paris into the
mixing cup to fill your form to a depth of

about one inch. Add water to the plaster, a
small amount at a time, and stir with a stick
or spoon until the plaster is smooth,
thickened and will pour slowly - about the
consistency of pancake batter.
Plaster of Paris
Form - made from the strips of a
cardboard milk carton or similar
material, cut about 3/4 to 1 inch wide
and up to 1 foot long
One of the following lubricants:
Vaseline, kitchen oil or grease,
petroleum jelly, shortening
Mixing cup and stick or spoon for
mixing the Plaster of Paris (Plastic
containers are desirable because
hardened plaster can be easily removed
from them by flexing the plastic and the
container may be used again.)
4) Pour plaster into the form to the depth of
 2 strips of cardboard (a milk carton
approximately three-quarters to one inch.
works well - or plastic strips from a
If you are making a cast of a track in sand
milk jug)
or loose soil, pour the mixture down the
stirring stick to avoid damaging the specimen. Fill the form nearly to the top to make
a stronger cast.
5) Leave the plaster overnight, or longer, if the weather and time permits. Once the
plaster has set carefully lift the cast off the specimen. A knife blade or spatula can be
helpful in lifting the cast. Brush the excess soil or debris away after the cast is
thoroughly dry.
6) Dry the plaster mold completely. In the middle of the summer it can be baked in the
sun for two or three days. In the winter it may be dried in a slightly heated oven
(approximately 100 F for approximately one full day, twenty-four (24) hours).