Fiberglass, a cloth material made from many fine fibers of glass, is a hard material often used to create copies of existing objects. In these copying processes, fiberglass is most often used as a casting material, meaning that the copy itself is made from fiberglass. This is useful for creating film props, automobile bodies, boat hulls and other items. However, fiberglass can also be used as a molding material to create an extra-strong mold that retains a sharp impression of the original object. The most common type of fiberglass mold is a two-part mold, which comes apart neatly to release an inflexible copy.
Instructions
1. Find a model object that you would like to create a mold for, or make your own model using craft foam and glue. Place the model object in a well-ventilated workspace, on a tabletop or counter that has been covered in plastic.
2. Create a center line on the model that divides the model into two equal halves. You can draw the line directly onto the model with a pencil or simply envision it while you work. On this line, build up a thin wall of modeling clay that is as high as you would like your mold to be thick. You can also approximate a taller wall by instead making a parting board out of cardboard or card stock, closing the holes with a small amount of modeling clay.
3. Apply wax mold release to the model object and parting wall, covering everything in several layers of wax. Buff out the bubbles and make sure that the wax is as smooth as possible. Over the wax, apply one coat of liquid mold release. Let the mold release dry.
4. Put on your latex gloves, safety goggles and vapor respirator. Mix together a small batch of resin with its catalyst, following the instructions on the packaging. Mixing directions often differ from company to company, so make sure that you are using the correct instructions for your particular product.
5. Apply the resin to one side of the object in a thin layer, starting with the corners and any deep crevices. Let the resin dry completely.
6. Apply a layer of gel coat over the resin, then let it dry for 30 minutes. Mix together another batch of resin and apply it over the gel coat, this time creating a thick layer.
7. Cut small strips of fiberglass cloth and lay them over the resin while it is still wet, so that the cloth soaks up the resin. Let this first layer of fiberglass dry for 30 minutes, then paint on another layer of resin and lay more fiberglass strips over it. Continue layering resin and fiberglass until you have the mold thickness that you want. Let this side of the mold cure for 12 hours.
8. Take apart the modeling clay wall or parting board, and clean all traces of clay from the model object. Repeat steps 3 through 7 on this side of the model object, laying down resin and fiberglass right up against the edge of the dried mold half.
9. Separate the mold halves and trim away any rough edges with a pair of scissors, or grind them down with a dremel tool.
