Choosing the Right Resin

About Resins


Choosing Composite resinsSo, you are starting a new project. You have your fabric chosen, your tools laid out and your designs are solid. But you haven’t decided on a molding resin, have you? It’s easy to overlook, when your busy comparing Kevlar to Carbon Fiber, but the resin you choose can have just as much an impact on your finished project. Molding resin selection can vary based on fabric compatibility, service conditions, and desired characteristics of the finished part.

There are generally three types of thermosetting resin to consider when approaching your project: Epoxy, Vinyl Ester, and Polyester. Here is a broad overview of what the three, including their characteristics, and what they should be used for.

Epoxy Resin

For composite parts that demand the ultimate strength, fabricators will use an Epoxy Resin. In addition to increased strength properties, epoxies also generally outperform polyester and vinyl ester for dimensional stability and increased bonding with other materials.


Epoxy Resin

High Strength Properties

Can be used in vacuum infusion applications

Easy to handle

Medium viscosity


Cannot be used with chopped strand mat

Not UV stable. This must be paired with a top coat when exposed to UV rays

Fibre Glast offers a host of choices when it comes to Epoxy resins. Our System 1000 Epoxy works great as a general purpose resin, while our System 2000 Epoxy, which offers the highest of strength properties which makes it great for structural aerospace. Our System 3000 and System 3300 are both high temperature epoxies, with the 3300 being perfect for exceptionally stable and long-lasting high temperature molds. For more information our our epoxies, visit the Epoxy store page.


Polyester Resins

Polyester Resins are the most widely used resins in the composites industry. Polyester Resins are less expensive, offer some corrosion resistance, and are more forgiving than epoxies. The majority of all fiberglass parts are constructed using Polyester Resins because they are easy to use, fast curing, and tolerant of temperature and catalyst extremes. Fibre Glast carries two different types of Polyester Resins, each with their own strengths and uses.

Polyester Molding ResinPolyester Molding Resin



-Easy to handle

-Rapid wet-out

-High thixotropic index (product won’t run on vertical surfaces)


-lower physical properties compared to more expensive resins


Our #77 Polyester Molding Resin is a general purpose polyester resin, ideal as a orthophthalic fiberglass resin for part fabrication and for building low cost molds. This resin is easy to work with, less expensive compared to it’s epoxy and vinyl ester counterparts, and is wax free, meaning you won’t have to sand being coats.

Isophthalic Polyester ResinIsophthalic Polyester Resin


-Dimensionally stable (minimal shrinkage)

-resists post cure problems

-can be used in food contact applications


-Slightly more expensive than general purpose polyester resins


The #90 Isopthalic Polyester Resin is perfect for making dimensionaly stable polyester molds, fabrication of corrosive service parts, and as a durable repair material for tank linings. The Isophtalic Resin boasts much better strength when compared to general purpose polyester resins, which allows it to be used in more demanding applications.


Vinyl Ester Resin

Vinyl Ester Resin is considered a hybrid of polyester and epoxy—meaning its handling characteristics, properties, and price generally fall just between the other two. It is important to note that, Of the three, vinyl ester resin will provide the highest corrosion resistance, temperature resistance and elongation (toughness.) Because of this, they are typically used when high durability, thermal stability, and corrosion resistance is needed.


Vinyl Ester Resin

-Extremely tough

-corrosion resistant

-heat resistant


-short shelf life (3 months)


Vinyl Ester resins are quickly becoming popular within areas of modern high performance composites. We offer the #1110 Vinyl Ester Resin, which is compatible with all of our fabrics, pigments and fillers. It is suitable for construction of most chemical storage and full tanks. Though we recommend testing the the tank for compatibility before putting it into service.

Still not sure which is right for your project? Read our full Learning Center Article About Resins. You can also reach us on our Facebook or our Twitter with any questions you might have. Let us know your thoughts in the comments below.


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1 Dave { 12.28.12 at 5:47 pm }

How long is lay up polyester good for…shelf life. How about gelcoat?

2 { 01.24.13 at 2:46 pm }

All of our products except Vinyl Ester Resin are guaranteed to have a six-month shelf life from date of purchase when stored in unopened containers and at ambient temperatures. Vinyl Ester Resin has only a three-month guarantee.

You can see our policies and guidelines for all our product here

But….many customers do report that in some instances they have had resin for 1 year and it was still useable (we just don’t guarantee it) . I hope this helps

3 Dave G { 03.05.13 at 5:54 am }

Where can I find cure times for your epoxy resins? I need to know how long to hold vacuum and keep my heat source on. Using 2060 hardener at 150 degrees.

4 { 03.06.13 at 6:09 pm }

The time is project dependent, and may be different based on the ambient temperature and thickness of the laminate. Our, product data sheet ( ) should give you direction on this question.

5 John { 03.08.13 at 1:02 pm }

I work mainly in urethane and polyester resins. For top coat is there a clear epoxy resin with low viscosity that can be sprayed with a cup-gun and that offers UV properties?

6 { 03.08.13 at 9:30 pm }

We carry a urethane coating resin (#3500 Clear Urethane Casting/Coating Resin) that gives epoxy parts a UV protective coat, but it cannot be sprayed.

7 Brian Smith { 03.18.13 at 4:05 pm }

I’m just getting started in cpoomposites. I’ve used some epoxies before but am curious about polyester. I’ve heard it smells quite bad and needs lots of ventilation. Is this true. Can I use it in my lab or should we work outside?
I’m not concerned with any real performance benefits between epoxy and polyester. We are just going to be making flat fiberglass panels that will be cut on the CNC router.
Thanks for your help

8 { 03.19.13 at 12:42 pm }

If you’re working in a shop, you definitely need great ventilation, but that goes for any resin. If you decide to work outside, make sure that it’s out of sunlight, the humidity is not high and the temperature stays above 60 F during the part’s cure schedule.

9 manuel { 03.19.13 at 1:00 am }

I need to fix a water tank, it have baffles, i need a resin that work in vertical position. what kind of resin should i use? .

10 Jim { 05.11.13 at 2:52 pm }

We have a fibreglass lined concrete swimming pool. The original fiberglass and resin (type unknown) are still in excellent shape. Polyester resins seem to chip and delaminate. Swimming pool paints (latex) and epoxy paints turn to chalk after just a couple of years. We have been told that vinyl ester resin and gelcoat is the only combination to use for swimming pools. Can you comment?

11 { 05.13.13 at 12:33 pm }

If you would like to speak with a Fibre Glast Customer Service Representative, please call 800-821-3283.

We would be glad to help you.

12 ed { 05.21.13 at 9:18 pm }

Iam covering a wooden boat with 4 oz glass and am looking for a clear finish, what is the best epoxy to use.

13 { 06.04.13 at 5:33 pm }

If you are tied to an Epoxy resin, we do not have an offering that will offer a clear finish. Our System 2000 Epoxy has a light amber tint. If you aren’t set on an epoxy resin, our #83 Polyester Laminating Resin sounds like it might be an appropriate fit for your application. That said, our resins aren’t formulated to yield the clearest finish. If you need additional assistance, feel free to call one of our Fibre Glast Customer Service Representatives, at 800-821-3283.



14 Rick Kraus { 08.23.13 at 1:51 am }

I”m putting in a new floor in my boat and i”m using 1,5 oz strand mat. What is the best resin for this application

15 { 08.23.13 at 1:01 pm }

Thanks for the question Rick. There are a few factors that can go into answering that question based on the boat design and use. You might be best served calling one of our Fibre Glast Customer Service Representatives, at 800-821-3283.

16 Paola { 09.30.13 at 9:32 pm }

I am doing an sculpture of plaster of paris, and I would like to apply on top of it a polyester resin, Please can you tell me if will work out the combination, I tried before but with fiberglass and worked perfect. Thank you!!

17 { 10.18.13 at 12:19 pm }

It used to be pretty common to make plugs or molds out of plaster of paris and then laminate with resin and fiber. That will certainly work. I’m not positive I was understanding your question though. If you need additional assistance, feel free to call our customer service line and we might be able to help you more. 800-821-3283 or

18 Felipe Jugo { 10.07.13 at 2:47 am }

I want to laminate a boat hull skin in glass and vinylester resin to minimize osmosis risk , and then laminate the internal structure in poliester resin to keep cost down. Is this OK? Is there a technical reason for not doing it?

19 richard { 10.19.13 at 3:14 am }

I am looking at building whitewater paddles what is the strongest most durable epoxy?

20 Jacob J { 11.18.13 at 10:02 pm }

Do you happen to know if I can use polyester resin/fiberglass to make a mold from a sulphor free, oil based clay sculpture? Any ideas would be incredibly helpfully! Thank you

21 Carbon Epoxy { 02.17.14 at 12:41 am }

Carbon is good to use as it is light and strong.

22 Turki { 05.10.14 at 10:03 am }

could anyone provide the sound properties of fiberglass with polyester resin? I need them for noise reduction enclosure
thanx in advance 🙂

23 Van { 06.18.14 at 9:49 am }

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24 { 06.18.14 at 2:32 pm }

You can certainly quote our blog, providing links to us.


25 curt { 06.23.14 at 4:14 am }

i have systen 2000 epoxy can i use vinyl ester on top of the epoxy on stringers

26 { 06.23.14 at 12:31 pm }

We would not recommend putting vinyl ester or polyester resins on top of epoxy. They do not bond with the epoxy.

27 Ben { 07.06.14 at 2:04 pm }

I’m rebuilding a fiberglass body kit for a truck. Can I lay vinyl ester resin over the original polyester(?) resin?

28 { 07.07.14 at 12:36 pm }

As long as you prepare the surface correctly, vinyl ester resin will bond and is suitable for use over polyester resin.


29 dan iverson { 07.07.14 at 1:37 pm }

I have a Coleman camper (Cheyenne series) made of a white polyester plastic type of material that has developed some cracking in a number of places on the roof surface, some of them over 1/8 of an inch wide. I was wondering if a “new” hard shell could be created by coating the roof with a resin of some kind

30 { 07.07.14 at 6:45 pm }

Depending upon the severity of the damage, you may or may not need to add reinforcement fabric for your repair.

If the damage is largely cosmetic, our #4116 polyester filler is a no-shrink solution that will be exceptionally rigid and strong. If you need a bit more strength, or have minor holes, you may need to start with our #4100 polyester fairing compound, a fibrous filler for structural repairs.

If there is structural damage, the best bet would be performing a full repair with multiple layers of reinforcement fabric. Check out the newest blog post about repairing canoes for an overview on the repair process.

31 Paul { 07.15.14 at 5:55 pm }

Which polyester resin is best for doing multiple layers of 1708 bixial fiberglass for a boat transom?

32 Rene { 12.09.14 at 8:56 pm }

I am new to the Fiberglas repair process…so with that said. I am trying to repair a Fiberglas horse saddle what type of material would be best for strength and durability? What is the process? Any advice would be very helpful.

33 abowser { 12.31.14 at 8:48 pm }

First, make sure that our products are right for your application. All of the fiberglass on our site is meant to be combined with resin to make a hard laminate part. If this is what you’re looking for, and if you’re new to the process, I’d suggest starting out in the Learning Center on our website, The articles and videos posted there will give you a foundation from which to begin. Let us know if you have any more questions!

34 Bud { 02.02.15 at 4:38 am }

I want to made molds for pouring lead out of carbon fiber. I tried the 2000 series resin but it did not hole up well with the 650 degree F. pouring temperature. Will the 3000 series resin hold up better under that temperature?

35 { 05.12.15 at 12:49 pm }

Most epoxy resins have maximum service temperature ranges significantly below 650F, including System 3000. Depending upon the size of the part you intend to make, and the efficiency of the thermal transfer, you might be able to make something work. That said, we do not have a recommendation for this application since it is well beyond the typical service temperature range for any of our resins.

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37 Susan Tang { 04.07.15 at 4:21 pm }

I would like to pick the correct resin for casting some kitchen ware. Can I use Isophthalic Polyester Resin to cast coasters and coat the inside of bowls/cups?

38 { 05.12.15 at 12:44 pm }

Our resins are designed only to be used to create reinforced laminates and are brittle when not reinforced. That said, our Isophthalic Polyester resin is appropriate for food-contact applications, as long the parts are produced appropriately.

39 nisrin { 06.21.15 at 6:36 pm }


I have a question please.
what is the appropriate resin/epoxy and curing agent to be used with unidirectional carbon fibers if the method of fabrication used is resin infusion or hand layup
Also, what is the shelf life of this epoxy and curing agent?
Thank you

40 { 06.23.15 at 1:29 pm }

While a high strength epoxy resin would typically be used with unidirectional carbon, application specific details could lead to other options. Feel free to contact our customer service department (800-821-3283) for to get more detailed information about your specific application.

41 Daq { 06.25.15 at 7:17 pm }

Hi, I’m looking into fabricating a mat/grate for the floor under my cooking equipment in a commercial kitchen. It seems that vinyl Esther would be best, my only concern is its resistance to oven/grill cleaner (sodium hydroxide). The contact would be occasional, please let me know what you think

42 Bill S { 07.14.15 at 7:00 pm }

What is a good resin for repairs to a “Royalex” canoe?

43 Lori { 09.26.15 at 8:00 pm }

We want to use quarter to fifty cent piece size rock to make a hearth on floor in front of fireplace. Our goal is to of course have stones show and have s smooth surface for cleaning. Is the product always shiny? And how heat resistant is it. Hot wood sparks are pretty hot! Which resin would be best?

44 jyoung { 09.28.15 at 1:36 pm }

Hey Lori,

It looks like the resin you are wanting is more of a casting resin as opposed to a laminating resin. Our resins are all designed to be used only as laminating resins (applied in thin layers, with reinforcement fabrics) so this isn’t really an application that we would have a recommendation for. We would, however, recommend that any resin you choose for this application be fire retardant due to the high risk of burning or charring (like you said, wood sparks can emit some serious heat) Unfortunately, none of our resins are appropriate for the type of application you’re looking for.

45 Mike { 10.17.15 at 5:51 pm }

I am repairing auto body “cancer” and wish to use vinyl ester resin and fiberglass cloth over the sandblasted steel. In your opinion, do you feel that I can get good results?

46 jyoung { 10.27.15 at 12:36 pm }

Hey Mike, Vinyl ester will bond adequately to sandblasted steel. Epoxy would offer an improved bond, but as long as the surface is adequately prepared (sandblasted, cleaned, lightly sanded to provide mechanical key, cleaned again) any of our resins should provide adequate bonding.

47 Dominic Vaillancourt { 10.27.15 at 8:11 pm }

I am looking at the possibility of building a Teardrop trailer.

I would like to use (Palette Pad) which is a honeycomb type cardboard for the walls and roof, what type of resin should I use, and which fiberglas fabric would be recommended for this project.



48 jyoung { 10.28.15 at 12:16 pm }

The type of resin and fabric will vary based on the strength properties of the palette pad you intend to use for the walls and roof, as well as the ultimate strength you need for the trailer. Additionally, it will depend on whether you are adding fiberglass for weatherproofing or structural purposes.

Depending on the strength you need, you’ll likely need to apply multiple layers of either 7 ounce or 10 ounce fiberglass fabric, followed by a surfacing fabric. If the ultimate strength isn’t as critical, either our #77 Polyester Molding Resin or our #90 Isophthalic Polyester Resin will work for this project. If you are trying to optimize the strength-to-weight ratio of the trailer (you might want to consider a different core material, if that is the case) you might want to use our system 1000 Epoxy resin with the #1025, 25-minute Pot Life Hardener, which will allow for fewer layers of fabric and subsequently less resin.

Now, if your palette pad is strong enough on it’s own and you are just looking to add a protective layer, our #77 Polyester Molding Resin and 2-3 layers of a lightweight fiberglass fabric (such as our #241 2 ounce or #262 4 ounce) will be sufficient.

If you want to get into further specifics, go ahead and give our customer service number a call at 800-838-8984. They’ll be able to get into specifics with you, and make sure you know what you’ll need.

49 Mary Ann Liu { 05.04.16 at 6:58 pm }

I am taking a 2 part mold off an exercise ball for an art project. Can i use Polyester resin on exercise balls? The type that people do stretching exercises on? Do I need a separator to protect the rubber?

50 Mary Ann Liu { 05.04.16 at 7:01 pm }

Thanks for taking the time to answer

51 Choosing your Composite Fabric - Fiber Glast Blog — Fibre Glast Blog { 07.27.16 at 1:27 pm }

[…] and About Reinforcements. Be sure to also check out our information in resins, including Choosing Your Resin, Polyester vs Vinyl Ester, as well as our white paper About […]

52 Beginners Guide: The basics of Epoxy Resins - Fibre Glast Blog — Fibre Glast Blog { 08.02.16 at 12:43 pm }

[…] in learning more about resins? Check out our other blogs, Polyester vs Vinyl Ester Resins, and Choosing the Right Resin. You can also check out our white paper, About Resins, over at the Fibre Glast Learning […]

53 Beginners Guide: The basics of Epoxy Resins – The Fibre Glast Blog { 08.04.16 at 4:40 pm }

[…] in learning more about resins? Check out our other blogs, Polyester vs Vinyl Ester Resins, and Choosing the Right Resin. You can also check out our white paper, About Resins, over at the Fibre Glast Learning […]

54 Ant { 08.06.16 at 2:11 am }

I made part out of carbon fibre that needed to be extremely flexible and thin. It was amazing. I then tried to do a similar part out of fibre glass and vinyl ester and I can hear it cracking and showing small stress fractures. Do you think it’s just because of the fabric or have I got my resin wrong? Thanks

55 Kevin { 10.15.16 at 2:52 pm }

i am looking for a 2 part resin that is uv resistant and has some strength properties . Planning on pouring small 2″ balls with a thru hole to run a rope thru with about 10 to 15 of these balls . the balls will ride up and down a pile-ling at my marina. and the line running through them will be tied to my 28′ boat. This will eliminating the constant adjusting of the mooring lines. Any suggestions on a product that will best be suited for this application ?

56 Joshua Leath { 10.19.16 at 2:22 pm }

Hi Kevin,
Thanks for the comment. For your application, you would want to go with a casting resin or urethane. A casting resin will be clear, if that’s what you are wanting. We do not stock casting resins, but our #90 should work fine. If you do not need it to be clear, a casting urethane allows you to choose the hardness (softer and less brittle, vs harder and more brittle). This would be our 60 Shore D (about as hard as a solid rubber tire) or our 75 Shore D (Very hard). Any of the resins or urethanes can also be colored with a pigment.

Free free to call us at 800-838-8984 with any questions!

57 Derek Johnson { 11.11.17 at 4:12 am }

Can you recommend an epoxy that will bond well with nylon? I know nylon is slick and doesn’t play well with most things.

58 Adam Smith { 12.26.17 at 1:25 pm }

Hello Derek. Unfortunately we do not supply an epoxy that will bond with nylon.

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