Fiberglass resin is a highly toxic material but useful for making props and other molded objects. Not impossible to work with, fiberglass resin can be used at home with some safety precautions like masks and ventilation systems. The molding and casting process itself is reasonably simple, and with some practice, can be performed by anyone. To mold your own fiberglass resin object using the two-part mold method, complete the following instructions.
Coat your template object or sculpture with a mold release agent, unless you are working with soft clay and are not concerned about the original sculpture being damaged. Mark the midline of the sculpture, from one side of the base to the other, and build up a thin wall of modeling clay along this line.
Create a mixture of gypsum and water in a large bucket, adding gypsum to the water until you have a creamy plaster texture to work with. Over a protected working area, apply your plaster mixture to one half of the sculpture, all the way to the modeling clay wall, creating an impression coat. Let the impression coat cure completely, for about six hours, then add another coat of plaster and a layer of burlap strips. Let this layer dry, then continue adding layers of plaster and burlap to the sculpture until you have a thick mold. Repeat this procedure on the other side of the sculpture.
Pull the plaster mold off of the sculpture, separating the modeling clay wall. Clean the inside of the mold free of clay, if necessary, then coat the inside of the mold with paint. When dry, paint the inside of the mold with a mold release agent known as polyvinyl alcohol.
Put on your vapor mask, and mix together a small amount of laminating resin and catalyst, following the instructions on your product's package. Paint an impression coat of the mixture onto the inside of both halves of the mold, brushing at the laminating resin until it sets.
Cut small strips of fiberglass cloth and lay them into the mold halves. Paint a coat of laminating resin over the fiberglass, then lay more strips of fiberglass over that. Keep applying fiberglass and laminating resin until you have the desired thickness and coverage. Let the casting cure for a few hours, until they are firm but still flexible. Pull the casting from the mold carefully, then place it back into the mold to finish curing. This way, you will not have trouble removing the casting later.
Trim away all excess fiberglass, then line the two halves of the casting up to see that they match properly. Tape them together with masking tape in a few places, and seal up the seam with more resin and fiberglass, removing the masking tape as you go.
File and sand down the seam, wearing a particle mask. If necessary, you can sand the resin underwater to avoid toxic dust.