Polyester Laminating Resin

FREQUENTLY ASKED QUESTIONS

• What is the difference between laminating resin and finishing resin?

  Polyester resin comes in two forms, a laminating resin that does not contain wax, and a finishing resin that contains wax. Polyester laminating resin remains tacky to the touch and does not cure in the presence of air, making it ideal for layups. Polyester finishing resin contains wax, which allows the resin to cure. Finishing resin is typically used as the final coat in a layup.
• What is the difference between laminating resin and gelcoat?

  Laminating Resin and Gelcoat are both polyester resins, use MEKP catalyst, contain styrene, and can be tinted with compatible colorants. However, Gelcoat typically contains ISO (isophthalic) resins that give it stronger UV and water resistance for use as a finish coat. Polyester Laminating Resin does not contain wax, is used in build layers only, is typically an orthophthalic resin, and has no UV resistance.
• What is the difference between polyester resin and epoxy resin?

  Polyester resin is used more for fiberglass layups or if you’re going to finish a repair with gelcoat, as the polyester resin will bond to the gelcoat better than epoxy. Epoxy is ideal for adhesive applications because it cures fully when applied as a thin film. Epoxy resin does not shrink when cured, while polyester resin does, based on the amount of resin that’s poured. Epoxy is also not naturally UV resistant and it will not bond to polyethylene.
• Do I need to sand when using laminating resin?

  No, sanding is not required between coats, or before a final coat with a polyester laminating resin.
• What is the shelf life of laminating resin once opened?

  Shelf life is about six months to one year once it’s opened. To ensure maximum stability and to maintain optimum resin properties, resins should be stored in closed containers at temperatures below 77 degrees Fahrenheit, and away from heat sources and sunlight. It’s important to store it in a cool, dry space.
• What color is the laminated finish?

  It comes clear, but with an amber tint. If aesthetics are important, look for products stating crystal clear.
• Can laminating resin be used for fiberglass layup on wood?

  Yes, it holds very nicely. Apply a coat to the wood first. This will allow the wood to absorb some of the resin. Then apply an additional generous coat to the wood and lay your fiberglass. Apply additional resin to saturate the cloth. Use a brush to tab in any angles or radius bends.
• Do I have to add wax in order for it to dry?

  Laminating fiberglass resin remains tacky unless you add wax to it for the final layers in your layup, or apply an airdry product, such as PVA (polyvinyl alcohol) to the surface. For a complete cure, you can also use a finishing type resin for the final layer, such as our TotalBoat Polyester Finishing Resin.
• Does it set up tacky or dry?

  It contains no wax to prevent the creation of an oxygen barrier that would cause it to cure, so it stays tacky and won’t sag while you’re building up layers. It requires a final coat of Polyester Finishing Resin containing wax to cure to a hard, tack-free finish. Alternatively, you can add a paraffin wax additive to the laminating resin before catalyzing with MEKP.
• What is the working time for this product?

  The gel time depends on the temperature during the time you are using it and how much hardener you use. Adjust the hardener level to slow down or speed up gel time. Cooler temperatures may require a higher percentage of hardener than warmer temperature conditions. At 70 degrees F, one teaspoon of hardener per quart of resin will give you about 20 minutes to Gel time, 2 teaspoons will give 15-20 minutes and 3 teaspoons will give about 10 minutes.