Open Molding Process

Contact-MoldingAt Beetle Composites we commonly use an open-mold, spray gun fiberglass manufacturing technique. Handheld spray guns are used to apply composites resin and gel coat materials to the open mold. A gel coat is applied first, then a resin, catalyst, and glass mixture. Materials, such as mat, foam, wood or metal may be hand-laid, and hand-held rollers are used to remove air. Once cured or hardened, the product is pulled and finished to the custom design specifications.

At Beetle Composites we utilize two open molding techniques hand: lay-up and spray-up.  However, we also utilize other molding techniques such as filament winding, press molding, centrifugal casting, pultrusion, and vacuum intrusion.

Hand lay-up

Hand lay-up is one of the most basic fabrication techniques for Fiberglass Reinforced Polymer (FRP) products and is also referred to as contact molding.  In this process a simple mold is coated with an appropriate release agent, resin, and special corrosion resistant glass called “C-glass”.  This initial resistant layer is significant because it provides a high-resin, low glass content corrosion barrier. The hand lay-up process uses a combination chopped –glass mat and woven continuous glass filament layered together with resin.


Spray-up is similar in nature to hand lay-up process and is also included in the general category of contact molding.  Simply put, the spray-up process is an automated way of depositing chopped glass onto a structure.  The spray-up method is particularly useful when filling a cavity or when glass mat or weave are too stiff for the design specifications.