Do-It-Yourself Guide to Polyester Plug and Mold Building

On the other hand, there is no quick or easy way to produce a quality polyester plug or mold. Good tooling is a precise painstaking craft. It starts with careful preparation of the pattern (plug) to the final building of the mold. The surface of the pattern must reflect the mirror finish desired in your mold. The building of the pattern must be exact to eliminate any faults that will ruin the mold.

An original plug can be used from wood coated with polyester or epoxy resin. It can be made of plaster, RTV silicone or foam. Your choice of plug-making material is limited only by your imagination. Plaster, foams and low density materials seldom last more than one mold. If several molds are to be pulled from the plug, a polyester and fiberglass plug can be used to make several molds.

The plug should be glossy and as defect-free as possible to minimize the amount of sanding and buffing of the mold. If the mold requires some cosmetic reworking, care must be taken to avoid changing its dimensions or features.

CAUTION: Do not use varnish or lacquer as the finish coating of a plug. The heat generated by the mold laminate can soften and attack these coatings.

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FIBERLEASE is best applied using a spray gun. Use high air pressure (80 to 100 PSI) and low output of liquid. Apply several thin coats followed by a heavier wet coat of approximately 2-4 mils. If spray equipment is not available, acceptable results can be obtained using a poly foam brush, lightly wetted with FIBERLEASE, and a delicate one-way brush stroke. Allow FIBERLEASE to dry at least 30 minutes or until tack-free and glossy.

CAUTION: FIBERLEASE cannot be applied over silicone based waxes.
Use Carnuba based mold waxes only.

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3. Scheduling

• Day One Build
  Mold building should be started early in the morning so you are ready to place the first layer of fiberglass on the mold in the afternoon.
• Day Two (Until Finished) Build
  Complete mold by laminating additional layers at one time. Lay up a maximum of three layers at a time, let cool after 3rd layer.
• Preliminary Curing
  Allow a minimum of five days before separating mold and plug.
• Final curing
  Allow a second five days after pulling mold from plug.

If spray equipment is not available, the gel coat can be applied with a brush. Brush the gel coat onto the plug with a very full brush load, brushing in one direction only. Keep the brush well loaded with gel coat. A mil gauge is very helpful in determining the 20 mil gel coat thickness when brushing or spraying the tooling gel coat

CAUTION: Do not allow tooling gel coat to cure completely as it may shrink and pull away from the plug. This means you should never leave tooling gel coat overnight or over a weekend without first laminating at least one layer of fiberglass. This is the most critical step.

Any defects in this layer such as blisters, voids and dirt contamination will transfer through to the gel coat. These imperfections will not always show up in a new mold immediately, but will appear after a few parts are pulled from the mold. One layer of 3/4 ounce or 1.5 ounce chopped strand mat is commonly used as a first layer, as it will help reduce dimpling, print-through and distortion. Always measure the catalyst accurately and strive to maintain a 33% glass to resin ratio. Try to finish the mold within a week if possible.

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After the laminate is finished, it is usually necessary to construct a cradle to support the mold. The cradle may be constructed of wood or steel, however it is important that the cradle be insulated from the mold when attaching it. This can be accomplished by using spacers between the mold and the cradle. Spacers can be cardboard, foam or Coremat and placed wherever the cradle will come into contact with the mold. Laminate the cradle in place with several layers of mat, being careful not to let resin seep into the spacer material.

After this is complete, allow the mold to cure a minimum of five days before pulling from the plug. and five days after pulling. Cosmetic repairs, if needed, and waxing can begin during the second five day period.

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Providing all of the above have been closely followed, your mold upon release should have an extremely glossy surface. The key is to prepare and maintain the mold in a condition that will give it a long life.

Start by applying six coats of wax using the same procedure as outlined in the preparation of the plug. It is advisable to use FIBERLEASE PVA for the first two parts, or more if release is difficult or sticking is encountered. When the parts release with a minimum of difficulty with no sticking, FIBERLEASE PVA is no longer needed. Rewax only when necessary, such as when parts become difficult to remove.

The following is a typical mold break-in procedure:

• Wax and polish mold six times
• FIBERLEASE PVA the mold
• Coat mold with catalyzed gel coat
• Laminate fiberglass onto the gel coat

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Many of the materials used in polyester plug and mold building are flammable, and can be hazardous to your health if used improperly. To reduce the hazard of fire or injury we recommend the following:

• Keep all flamable materials from flames or other ignition sources.
• Wear appropriate latex or solvent resistant gloves{Keep off skin.}
• Wear safety goggles
• Use in a well ventilated area or use a respirator
• EXERCISE COMMON SENSE AT ALL TIMES
• ALWAYS, WITH EVERYTHING, KEEP AWAY FROM CHILDREN
• Read all instructions and information provided with materials being used
  

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• NEVER PUT LIQUID MATERIAL IN THE GARBAGE .
• DISPOSE OF HAZARDOUS WASTE IN ACCORDANCE WITH LOCAL AND STATE REGULATIONS PERTAINING TO THE DISPOSAL OF SUCH MATERIALS.
• If you are unsure as to what to do with leftover material call your supplier for direction.