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How to Make Fiberglass Molds

Fiberglass molds are mostly used in the preparation of items with complex shapes. Molds are the exact representations or replicas of the objects to be produced in bulk. Fiberglass mold making is carried out for mass production of items needed for daily use.
Shashank Nakate
Last Updated: Jan 4, 2019
Fiberglass is prepared from small fibers of glass that are woven into threads. It is fireproof and resistant to damage caused by sunrays. This material is also resistant to cold temperatures.
In the process of casting and mold making, brittle polyester resin is mixed with fiberglass to offer the required strength and stability to the final product; the material is especially strong along its axis (of the fibers) in terms of compression and tension.
For a strong and robust material like fiberglass, the weight is surprisingly less. All these properties and qualities make fiberglass quite a useful material. It has many applications and is used for making pipes, roofing, cladding, automobiles, door skins, tubs, etc.
Procedure for making fiberglass molds is simple, however, it takes a few days (and not hours) to create a mold. The materials required for preparing molds are inexpensive.
Thus, one can make fiberglass molds at home itself without having to worry about the cost incurred. A detailed information on how to make fiberglass molds is presented through following paragraphs.
Fiberglass Mold Making
The process of fiberglass mold making involves the activity of preparation of plug. A plug is used for making molds. Plugs are an exact representation of molds that you are going to make.
They could be prepared with the help of materials like plaster, wood, putty, formica or sheet metal. One should always stay careful about the dimensions of plugs, so that the molds you would be making attains a perfect shape.
If you are going to use materials like plaster, wood or putty for making plugs, then it becomes necessary to apply lacquer resin for sealing the pores. Plugs have to be buffed and sealed with TR-311 and TR-301. The plaster has to be oven-dried before sealing it.
A mold-release paste known as Partall Paste #2 should be applied after sealing the plug. The paste should be allowed to dry before applying the next coat. In this manner, 5 coats of the paste should be applied to the surface of plug.
The next step in the process is to spray the plug with polyvinyl alcohol (PVA). Three coats of PVA should be applied and the plug kept for drying for about 30 minutes. The plug should then be covered with the MEK peroxide hardener followed by application of gel coat. The coat should be applied by means of a bristle roller.
Care should be taken to see that the gel coat is free of wax. A tooling gel coat, if used for the purpose of coating, should help increase the longevity of mold. Two layers of gel coat must be applied with a gap of 4 hours to allow complete drying. It takes about 24 hours for the gel coat to dry completely.
Application of skin coat is the next step in this process. At first, a fiberglass mat should be laid on the surface. Once the fiberglass layer is applied, a polyester resin should be spread with the help of roller.
Air bubbles (if any) and white fibers should be removed before the coat dries up. Next layer of resin should be applied after 24 hours. In all, three layers of resin should be applied to the surface.
The fiberglass should be removed after the skin coat dries completely. It takes several days for the complete drying of skin coat. A metal-cutting blade should be used for cutting the excess resin. A stirring stick or plastic wedge need to be used to separate the mold from the plug.
The mold should be polished with the help of a 220 grit sandpaper followed by applying the Partall Paste #2. A heavy-duty cleaner and sealer glaze should then be used to give the mold a clean and sparkling look.
Fiberglass has many applications and it is used in making a variety of items. The different instruments or items ranging from fiberglass pipe insulation to fiberglass dune buggies are available in the market. The process of fiberglass mold making being easy to carry out, it is used in creating molds for a variety of items needed for daily use.