In fiberglass moldmaking, complex designs are molded into a reinforced plastic form perfect for casting multiple design copies. Fiberglass itself is used in both processes as the material for the mold and for the finished product. These molds are relatively simple and inexpensive to make, and can last a long time, often through hundreds of casting sessions.
Identification
Fiberglass, also known as glass fibre, is actually made from fibers of glass. The fibers are made into thread and woven into fabric so that it keeps some textile characteristics and some glass characteristics. Usually, fiberglass is used in fiber-reinforced polymers and glass-reinforced plastics due to its strength and versatility. Fiberglass is fireproof, resistant to sun damage and lasts an extremely long time. In moldmaking and casting, fiberglass is mixed with brittle polyester resin to produce an immensely strong product.
Function
Fiberglass molds are used in a variety of industries, most notably that of boats and automobiles. Vehicles, usually made of heavy metals, benefit from casting the body in lightweight fiberglass, which cuts down on the amount of power needed to move the vehicle. Aside from more technical industries, fiberglass is also a common material in theater and artistic moldmaking. Fiberglass molds are used to make props for stage and film, and amateurs use theater molding techniques to create Halloween and costume props.
Types
Most often, molds made with fiberglass are either 2-part, in order to cast both sides of a 3-dimensional object, or 1-part molds that take the shape of only one side of the desired design. Both mold types involve the use of a plug, or copy of the object about to be molded. The plug is usually made of altered foam and coated in a mold release agent to keep the plug from sticking to the mold materials.
Features
Fiberglass molds are largely a series of chemical layers applied atop one another to form a hard shell. The plug is first coated with a gel to fill in all the small details and give the mold a smooth, glossy finish. Sometimes more than one coat of gel at different levels of viscosity is required. Following the gel coat, layers of fiberglass are applied, followed by coats of resin. All these layers dry to form an incredibly durable mold thickness, and then the plug is released from the mold. The casting process works in much the same order and with many of the same materials.
Considerations
Manipulation of the fiberglass can sometimes include some difficulties. Air bubbles can ruin a mold and must be removed using a roller, or avoided entirely by properly wetting the fiberglass cloth with resin. There are also safety concerns to be considered in use of the fiberglass mold materials. Although the materials have come a long way from the early days of little quality control, there are still some dangers. Polyester resin is extremely toxic and should never be touched or ingested, and some of the extra fiberglass moldmaking chemicals a person may be working with can be irritating to the skin or downright poisonous.
