Polyester for Beginners

What can be done with polyester? How do you work with polyester? How do you process it and what do you use to create a nice finish? Read it here and order the products here!

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What is polyester resin and what can you use it for? In this article, we explain the basics of working with polyester resin. At Polyestershoppen, you will find all the materials you need to start your polyester project. Our specialists are also ready to advise you and help you get started with your project. So feel free to contact us!

What is polyester resin?

Polyester is a synthetic resin that hardens after adding a hardener. This process is irreversible, meaning polyester cannot be remelted once cured. Polyester does not rot or rust and can be processed with a minimum set of tools. With a polyester repair kit, you can easily carry out minor repairs to items like caravans, boats, or swimming pools.

Polyester is usually combined with fiberglass to produce a strong, impact-resistant, and rigid product. Examples of polyester products include boats, ponds, swimming pools, car bumpers, gutters, artwork, scooter fairings, waterproof linings, and much more.

Advantages of working with polyester:

Polyester does not rot or rust.
An inexpensive and easy method to produce plastic items or perform repairs.
Suitable for a wide range of applications.
Polyester is a strong and rigid system.

Combining polyester resin with fiberglass is called laminating. The resulting plastic material is referred to as a laminate, named after the various layers of fiberglass it consists of.

Polyester is ideal for products where design freedom comes first. Polyester with fiberglass is always laminated against a mold (which can be temporary or permanent). This temporary mold can be made from various materials and can also become an integral part of the structure. Examples of molds include: polyester molds as well as molds made of wood, foam, plaster, or chicken wire. You can manufacture products inside a mold or apply a protective lining over objects. In short, as long as you have a substrate to laminate the polyester against, it can be made using polyester.

Polyester products can be finished in several ways. Against a smooth mold, gelcoat can be applied: a fully colored layer of approximately 0.3 mm thickness based on polyester. This layer adopts the exact surface texture of the mold, usually aiming for a mirror-smooth finish. For filling small pinholes and achieving a smooth finish, use polyester putty. This product cures quickly and is easy to sand.

	Application	Properties
RESION Polyester laminating resin	Laminating with glass mat Creating adhesives and fillets Polyester repairs	Impact-resistant Fast curing Easy to apply Cost-effective Tack-free curing Low styrene emission
RESION Polyester casting resin	Casting ornaments Embedding organic materials (flowers, insects) Casting figurines Jewelry	Fast curing Highly transparent May show shrinkage (approx. 5%) Adjustable reactivity UV-resistant
RESION Vinylester resin	Mold making Shrinkage-free lining Chemically resistant floors, horse trailers, livestock transport, walls, etc. Feeding troughs	High temperature resistance Very high chemical resistance Stronger than polyester Fast curing Osmosis resistant
RESION Polyester topcoat	Finishing polyester ponds and swimming pools Finishing fiberglass laminates Repairing gelcoat damage	Fast curing Easy application High layer thickness Thixotropic Tack-free curing Good water resistance
RESION Polyester gelcoat	Finishing polyester ponds and swimming pools (1st layer) Color layer in molds	Fast curing Easy application High layer thickness Thixotropic Good water resistance
RESION tooling gelcoat	Surface layer for durable molds	High temperature resistance High scratch resistance High gloss level Low porosity
RESION tooling resin	Construction material for durable molds	Shrinkage-free curing Suitable for rapid laminating methods Tack-free curing 5 mm thickness can be laminated wet-in-wet
RESION sanding gelcoat	Carrosserie repair on polyester parts For paintable polyester products	Easy to sand Excellent adhesion with various paint systems Thixotropic High layer thickness Easy application
Polyester putty	Fine finishing of polyester laminates Repairing scratch damage Filling metal parts (auto bodywork) Filling bumpers	Fast curing Easy to sand Good adhesion to various substrates Not water-resistant (use epoxy putty underwater)
Polyester glass fiber putty	Filling holes Repairing cracks	Stronger than standard polyester putty Fast curing Crack-resistant Good adhesion to various substrates Not water-resistant (use epoxy putty underwater)

A polyester topcoat can be applied on the reverse side of a polyester product or when coating an object. This coat is also an approximately 0.3 mm thick layer colored through and through, but its surface texture depends mainly on the application method (brush, roller, or spray) and will always feature a semi-gloss finish with some light texture. It is possible to sand this topcoat smooth and/or polish it to a high gloss.

Polyester resin projects

Polyester has many applications. For several common projects, we have prepared detailed guides:

TIP: Do you have a project in mind but would like some advice first? Contact our customer service team. All of our staff members have hands-on experience with polyester and can assist you with your project.

Reinforcement fibers

When working with polyester resin, we usually use chopped strand mat (CSM). This mat is made of randomly oriented glass fibers roughly 5 cm long. These fibers are bound together by a binder that dissolves in polyester resin. Applying polyester resin to the mat softens it, allowing it to conform easily to the shape underneath. Once cured, the final product derives its structural strength from the glass fibers and maintains its shape via the resin matrix.

	Application	Properties
Fiberglass mat 225g/m²	Suitable as first layer behind gelcoat Suitable as first layer over styrofoam using styrene-free polyester Suitable as top layer for a finer finish on fiberglass laminate	Thickness approx. 0.5 mm Resin consumption 500g/m² Fine texture
Fiberglass mat 300g/m²	Suitable for polyester repairs Suitable for coating wood (2x 300g/m²)	Thickness approx. 0.7 mm Resin consumption 700g/m²
Fiberglass mat 450g/m²	Universal application For fast layer and thickness build-up Suitable for mold building	Thickness approx. 1 mm Resin consumption 1000g/m² Cost-effective
Surface tissue 30g/m²	Suitable as first layer behind gelcoat Suitable as first layer in mold building Suitable as top layer for a smoother finish on fiberglass laminates	Thickness approx. 0.1 mm Resin consumption 100g/m² High chemical resistance Prevents print-through on gelcoat
Woven roving 300g/m2	Suitable for extra strong laminate when alternated with fiberglass mat Alternate woven roving with fiberglass mat 300g/m²	Increases impact resistance Thickness approx. 0.5 mm Resin consumption approx. 500g/m²
Woven roving 600g/m2	Suitable for extra strong laminate when alternated with fiberglass mat Alternate woven roving with fiberglass mat 450g/m²	Increases impact resistance Thickness approx. 1 mm Resin consumption approx. 1000g/m²
Spherecore 3 mm	For extra rigid polyester laminates For lightweight polyester laminates Suitable for laminating curved shapes	Increases stiffness Faster build-up of thickness Thickness approx. 3 mm Resin consumption approx. 1800g/m²
Spherecore 4 mm	For extra rigid polyester laminates For lightweight polyester laminates Suitable for laminating curved shapes	Increases stiffness Faster build-up of thickness Thickness approx. 4 mm Resin consumption approx. 2400g/m²

How to mix polyester resin?

Never mix more polyester resin than you can apply within 10 minutes. Approximately 2% hardener is added to polyester resin.

Never mix excessive amounts of resin at once.
Use a pipette for small quantities of hardener (< 5 ml).
Determine the hardener ratio based on the ambient temperature.
Mix the resin and hardener thoroughly, scraping along the bottom and sides of the mixing cup.

How much polyester hardener do you need for polyester laminating resin?

The chart below indicates how much hardener you need for polyester laminating resin.

	Hardener
	12-17 ℃	18-23 ℃	23-30 ℃
Resin:	2.5%	2%	1.5%
100 grams	2.5 ml	2 ml	1.5 ml
250 grams	6.25 ml	5 ml	3.75 ml
500 grams	12.5 ml	10 ml	7.5 ml
1000 grams	25 ml	20 ml	15 ml

How much polyester hardener do you need for polyester casting resin?

The chart below indicates how much hardener you need for polyester casting resin.

	MEKP	Working time	Curing time
Thickness 1 cm	1%	25 min.	10 hours
	1.5%	22 min.	3 hours
	2%	20 min.	2.5 hours
Thickness 3 cm	0.4%	40 min.	2 hours
	0.7%	27 min.	1.5 hours
	1%	25 min.	45 min.
Thickness 6 cm	0.3%	48 min.	45 min.
	0.35%	43 min.	30 min.
	0.4%	40 min.	30 min.

Laminating

Laminating is the process of building thickness and strength using reinforcement materials such as fiberglass mat and polyester laminating resin. The reinforcement material is thoroughly "wetted out" with the polyester resin using a brush or roller.

Commonly used tools during laminating:

TIP: We also offer complete tool kits containing all the essential accessories used during laminating.

Finishing polyester with polyester topcoat

After laminating, the laminate surface may feel somewhat rough. To finish the laminate and enhance its weather resistance, you can apply a polyester topcoat. Lightly sand the laminate using 60-grit sandpaper to prepare it for topcoat application.

In the video above, Herman demonstrates how to finish polyester with a polyester topcoat. Once cured, your product is protected against weather conditions and displays your desired color.

Polyester repair kit

Purchase your polyester repair kit at Polyestershoppen.nl. Our kit is fully equipped with all the necessary tools to perform a variety of repairs—everything is included! Easily repair holes, cracks, and fractures in polyester items. In addition to small repair kits, we also supply polyester repair packages for larger projects, such as our laminating kit.

Personal protection

Styrene vapors emitted by polyester are harmful to health and the environment. Ensure adequate ventilation in your workspace and preferably wear a half-mask respirator, especially in confined spaces. Make sure to avoid skin contact with polyester resin and hardener by wearing appropriate gloves, such as nitrile gloves or work gloves.

Other commonly used safety equipment:

Safety glasses
Vapor mask with A2 organic vapor filters
Full-face mask (for full face protection) with A2 organic vapor filters

TIP: Polyestershoppen offers a complete personal safety kit containing all the protective gear required when working with polyester.

Have more questions about working with polyester?

As you have read in the article above, working with polyester is straightforward. On this page, we have explained to the best of our knowledge how polyester is processed, the options available, and what to keep in mind during application. There are countless possibilities when working with polyester. Whether you are building swimming pools, shower enclosures, automotive parts, furniture, or artwork, polyester can be applied in almost any situation. The possibilities are virtually endless. Do you still have questions after reading this article, or do you need advice for your specific project? Feel free to contact our specialists. They are happy to assist you!