Join us in the latest installment of our educational series as we break down the essential lingo of fiberglass craftsmanship. Whether you're a seasoned professional looking to brush up on your terminology or a novice eager to start your first project, this series is your go-to resource for becoming fluent in the language of composites.

Selvage- The woven-edge portion of a fabric parallel to the warp, finished off so as to prevent the yarns from unraveling. Fiberglass tape typically has a selvage edge. It gives it a nice clean look.

Mold Release -  Also known as a release agent or parting film, depending which kind is being used. The two most commonly used mold releases are a carnauba based wax and PVA (film).  Mold release is used to allow parts to be easily removed from the original plug  or the mold. Plus it adds a durable surface finish to the part and keeps both the part and the mold from being damaged during production.   A mold release is essential when breaking in a new mold.  It ensures  your part will separate from the mold cleanly rather than sticking to it.

Aramid- A type of highly oriented organic material derived from polyamide (nylon) but incorporating aromatic ring structure. Kevlar and Nomex are common name brands for aramid.  It is known for its impact and abrasion resistance. It is used in bullet-proof vests, motorcycle racing cloth and gloves.

De-lamination- Separation of the layers of material in a laminate, either local or covering a wide area.  This can occur in the cure or subsequent life.

One inch brush and stir stick cured in polyester resin (without a reinforcement).

Resin- In reinforced plastics, the material used to bind together the reinforcement material (fiberglass cloth). The matrix. Most resins are polymers. The most common resins in the fiberglass industry are polyester, vinyl ester and epoxy. Resin holds the reinforcement together and helps it conform to the wanted shape.  Resin fills the fiberglass weave when laminating.

Tack-free- A condition in which a plastic material can be dented with an inert object without sticking to it. It is indicative of a definite stage of hardening. A laminating resin will cure with a tack (stick) unless a surfacing agent or finishing resin is used. A finishing resin has wax that will rise to the top when  cured.  This will create a nice hard finish.

Fiber content- The amount of fiber present in a composite. This is usually expressed as a percentage volume fraction or weight fraction of the composite.

Cast- To form material into a certain shape by pouring it into a mold and letting it harden without applying external pressure.

If you want to see a comprehensive list of composite/ fiberglass definitions, all in one place, you can check it out here- Composites Glossary. Save